Take home points: July 2015

Mast cell interactions with B and T cells
• Mast cells communicate with other cells by:
o Releasing chemicals to tell another cell to do something
o Other cells releasing chemicals to tell mast cells to do something
o Moving right up against other cells, which allows the cells to “talk”
• B cells are white blood cells that make antibodies and protect against infections.
o Mast cells can tell B cells to make IgE, an allergy antibody.
o When mast cells touch B cells, the mast cells can release IL-6 which tells B cells to live longer.
o Mast cells can tell B cells to make IgA, an antibody.
• T cells are white blood cells that have many functions.
o T cells and mast cells are found close together in many inflammatory conditions, like ulcerative colitis.
o Activated T cells can activate mast cells.
o Mast cells can tell T cells to proliferate and produce inflammatory molecules.
o A kind of T cell called Treg (T reg, like in regulatory) cells can make mast cells harder to activate and interfere with degranulation.

Mast cells in kidney disease
• Kidney disease is often not identified until 60-70% of functional kidney cells have been damaged beyond repair.
• Mast cells are rare in healthy kidneys.
o Damaged kidneys can have up to 60x the normal amount of mast cells.
o Mast cell count is not related to disease severity.
• Atopic disease, like atopic dermatitis and allergic asthma, is linked to idiopathic nephrotic disease, kidney disease of unknown origin.
o The nephrotic disease and atopic disease could be manifestations of the same overarching condition.
o In patients with both, IgE levels are high.
• Tryptase is elevated in some patients with kidney damage.
• Mast cells are responsible for bringing other inflammatory cells to the damaged kidney.
• Mast cells can cause fibrosis in kidneys.
• In some roles, mast cells can protect kidneys from damage.

Regulation of mast cells by IgE and stem cell factor (SCF)
• Mast cells are mostly regulated in two ways
• IgE binds to the IgE receptor (FceRI) on mast cells and activates them
o Activation by IgE results in degranulation and secretion of mediators
o IgE induces mediator release by affecting the amount of calcium inside mast cells
• Stem cell factor (SCF) binds to the CKIT receptor on mast cells and tells them to stay alive
o SCF also increases degranulation and production of cytokines
o SCF helps mast cells to adhere to other cells

Mast cells in vascular disease: Part 3
• Mast cells are involved in the formation and growth of aneurysms
• Activated mast cell populations are increased in vessels that rupture
• Chymase, a mast cell mediator, can degrade vessels and increase risk of rupture
• Leukotrienes contribute to aneurysm formation

The effects of cortisol on mast cells: Part 2 of 3

Glucocorticoids, like cortisol, can affect mast cells in many ways. As I discussed in my previous post, there are many ways for mast cells to release mediators when activated. In all of these pathways, there are many molecules involved that carry the signal, like people passing the Olympic torch. In mast cells, one of the molecules that suppresses inflammatory activation signal is called SLAP (yes, really).  Cortisol increases the amount of SLAP in mast cells so inflammatory activation signals are suppressed.

An important step in degranulation is changing the amount of calcium inside the cell and moving it to different parts of the cell. In some studies, glucocorticoids can affect this movement of calcium. Other studies have found that in some pathways, glucocorticoids don’t affect calcium movement, but instead interfere with things like the IgE receptor.

Cortisol is also thought to directly inhibit stem cell factor (SCF) binding to the CKIT receptor. When SCF binds to the CKIT receptor, this sends a signal to the mast cell to stay live.  This means that taking glucocorticoids can let mast cells die at the appropriate time. SCF also tells mast cells to go to inflamed spaces.  By blocking this signal, glucocorticoids suppress inflammation.

One of the ways that molecules carry a signal is by changing the next molecule in the pathway. A big way that cells changing molecules is by chopping off a piece of them called a phosphate group.  This is done by special enzymes called phosphatases.  Glucocorticoids affect the availability of phosphatases so they aren’t able to get to the right part of the cell to carry the signal.  When this happens, there is less activation and less histamine release.

Arachidonic acid is the molecule modified to make eicosanoids (leukotrienes, thromboxanes and prostaglandins.) Glucocorticoids directly interfere with the production of these molecules in multiple ways.  The first way is by interfering with COX-2, one of the enzymes that makes prostaglandins.  Another way is by preventing arachidonic acid from being released to a place where they can be turned into leukotrienes, thromboxanes and prostaglandins.  This occurs because glucocorticoids increase the amount of a powerful anti-inflammatory molecule called annexin-I.  Annexin-I inhibits the molecule that releases the arachidonic acid, called phospholipase A2.

Annexin-I was the subject of an important paper earlier this year. In trying to identify exactly how mast cell stabilizers like ketotifen and cromolyn work, the researchers discovered that treatment with mast cell stabilizers decreased degranulation and increased annexin-I made by mast cells.  They also found that glucocorticoids had the same effect.

References:

Oppong E, et al. Molecular mechanisms of glucocorticoid action in mast cells. Molecular and Cellular Endocrinology 2013: 380, 119-126.

Varghese R, et al. Association among stress, hypocortisolism, systemic inflammation and disease severity in chronic urticaria. Ann Allergy Asthma Immunol 2016: 116, 344-348.

Zappia CD, et al. Effects of histamine H1 receptor signaling on glucocorticoid receptor activity. Role of canonical and non-canonical pathways. Scientific Reports 2015: 5.

Coutinho AE, Chapman KE. The anti-inflammatory and immunosuppressive effects of glucocorticoids, recent developments and mechanistic insights. Mol Cell Endocrinol 2011: 335(1), 2-13.

Sinniah A, et al. The role of the Annexin-A1/FPR2 system in the regulation of mast cell degranulation provoked by compound 48/80 and in the inhibitory action of nedocromil. International Immunopharmacology 2016: 32, 87-95.

IgE-independent anaphylaxis; or, I haven’t been this excited on a Tuesday night in a long time

Mast cell patients are intimately familiar with the phenomenon of testing positive for allergies to things you know aren’t problems and negative for things that almost killed you.  If you ask any health care provider what the allergy antibody is, they will say it is IgE.  And for the most part, that is true.  But mast cell patients suffer reactions that do not demonstrate an IgE pathway to their allergies and anaphylaxis, and it is reason most of us suffer for years before being diagnosed correctly.

The idea that anaphylaxis is a function directly executed by IgE is a deeply ingrained part of western medicine.  In this model, IgE specific for an allergen binds to the allergen, and binds to the IgE receptor on mast cells and basophils, resulting in massive degranulation.

This is the classic model of anaphylaxis, with some creative license:

  1. You come into contact with something. Let’s say it’s Peanut, an anthropomorphic peanut.
  2. Immune cells called B cells think they once saw Peanut in a dark alley behind a bar. Peanut could have been waiting for a ride like any responsible peanut who has been drinking, but dark alley = shady = Peanut is trouble.
  3. The B cells make “Wanted!” posters with a picture of the peanut on it. Many, many posters.
  4. The B cells make lots of IgE to make sure every cell in the body sees the Wanted! posters. There will be nowhere for peanuts to hide. (I swear that as I was typing, I just heard the theme to the Good, the Bad and the Ugly.  I SWEAR.)
  5. Everyone knows that Peanut is a bad guy. They have seen the poster many times.  They do not need to see it again.  Do not show the poster again.  WE KNOW PEANUT IS BAD, IGE.  GO HOME, IGE, YOU’RE DRUNK.
  6. You guys know what happens next.  Peanut shows up.
  7. Someone remembers that IgE has been coming around the bar with the poster of Peanut. Peanut = bad guy.
  8. Everyone is hoping that if they tell IgE where Peanut is that IgE will leave them alone. No one really likes IgE but he is making such a big deal about Peanut and maybe Peanut is bad.  A little bad.  No one really knows but they know they do NOT want to deal with IgE if Peanut gets away.
  9. IgE and Peanut have a Western style gun duel at high noon. IgE captures Peanut by binding to him.
  10. While IgE is bound to Peanut, he also binds to a mast cell, which is like home base. IgE knows that Peanut is trouble and he is part of a Peanut gang and they are all bad, too.
  11. Mast cells deploy the tanks, duckboats, submarines, helicopters and fighter planes in the early allergy response to fight the Peanut gang. This causes massive inflammation with effects throughout the whole body.  Mediators released in the early response include histamine and tryptase.
  12. Mast cells start building more defenses and release them a little at a time later on in the late allergy response. Mediators released in the late response include prostaglandins and leukotrienes.

But we all know that it doesn’t always happen like this, because mast cell patients often have normal tryptase and IgE despite having a massive anaphylactic event, or even normal histamine or prostaglandins.

Last month, a comprehensive paper described alternative anaphylaxis pathways in mice that may be analogous to what is happening to mast cell patients having anaphylaxis that is not mediated by IgE.  That is to say, this pathway needs more research to know for sure if it is what is happening to us, but I have been watching the literature on this closely for a while and I100% think this is real.

There have now been multiple reports of the ability to induce anaphylaxis in mice while interfering with the IgE allergy pathway (either by not making IgE or the IgE receptor, or by treating the mice with anti-IgE, which blocks the IgE from binding to the receptor). Scientists found that by anaphylaxis could be mediated by IgG if the trigger was given intravenously. In particular, they were able to identify the murine IgG2b as the antibody subclass responsible.  In mice, IgG2b can cause anaphylaxis when IgE is not able to participate, at all.

The most important mediator in IgE anaphylaxis is histamine.  But the most important mediator in IgG anaphylaxis is platelet activating factor (PAF).  PAF levels have been linked with severity of anaphylaxis previously (I wrote a post about this around this time last year).  This could explain why many patients have normal tryptase, n-methylhistamine or histamine levels despite a very short amount of time elapsed from anaphylaxis. This is not a histamine show.  And maybe the reason so many mast cell patients cannot get complete relief despite taking huge doses of antihistamines is because histamine isn’t the PRIMARY issue.  (Author’s note: Please do not stop taking your antihistamines.  I love my antihistamines.  Just saying I think maybe there is something happening above histamine in these reactions.)

It’s also not just a mast cell show.  IgG can activate basophils, monocytes and macrophages, and neutrophils to release PAF.  Human neutrophils can mediate IgG dependent anaphylaxis when infused into mice.  So now we have a mechanism for anaphylaxis that is not IgE independent – it can also be mast cell independent.  Mind blowing. (Worth mentioning here that the phenomenon of mast cell independent anaphylaxis is not new or specific to IgG anaphylaxis – groups have found instances of mast cell independent anaphylaxis for almost thirty years.)

PAF levels are much higher in anaphylaxis patients than in control patients, and the enzyme that degrades PAF, called PAF acetylhydrolase, is much lower. It is important to note that binding at the IgE receptor can also produce PAF, but that also causes degranulation and release of histamine and tryptase, which seems to be absent in some patients.

To induce IgG mediated anaphylaxis, you need more allergen than for IgE anaphylaxis.  A lot more. 100-1000x more.  So in mice that have both IgE and IgG for peanut (not really peanut), doesn’t it seem like the IgE would react first to the peanut, and you would have IgE anaphylaxis?  But that’s not what happens.  What happens is that the IgG scoops up the peanut faster than the IgE can.  The IgG can block IgE anaphylaxis.  (WHAT UP MAST CELL PATIENTS DOING WAY BETTER ON IVIG?!?!)

IgG anaphylaxis in mice has been exclusively isolated to triggers administered intravenously.  The reason this fact matters is because of the frequency with which people (who don’t always have mast cell disease) have anaphylaxis to intravenous antibody treats, like IVIG, monoclonal antibodies for treating various diseases, or transfusions (which contain IgG antibodies). Treatments of this kind provide a huge influx of allergen. This pathway favors IgG anaphylaxis over IgE anaphylaxis because of how the IgG will scoop the allergen up (see previous paragraph).

As a final aside, there is also the curious fact that a group of patients with CVID (common variable immunodeficiency, a primary immunodeficiency disease) have a mutation that makes one of the IgG receptors found on cells like mast cells WAY more active.  The CVID patients with this mutation also have antibodies to IgA and experience anaphylaxis after IVIG.

I know I have gone on and on but this is the most exciting thing to happen to tryptase and histamine normal anaphylaxis patients in the last decade, at least.  There is SO much work that needs to be done.  Mouse and human mast cells are different.  Mouse and human IgG antibodies are different.  They could not induce food allergy in mice with an IgG dependent mechanism.  We need to pursue research on the role of PAF specifically in anaphylaxis patients with normal tryptase and histamine.

But now, when you tell your doctor that anaphylaxis is not always IgE dependent, you can give them a reference to a solid paper that fairly describes the findings, the caveats and the strengths of the current research on IgE independent anaphylaxis.  And it’s not just speculation. PEOPLE OUTSIDE OF MAST CELL DISEASE RESEARCH GROUPS ACKNOWLEDGE THAT THIS IS REAL.  IGE INDEPENDENT ANAPHYLAXIS IS REAL.

Boom.

Someone hold my Epipens while I make my dog dance with me.

Reference:

Finkelman FD, Khodoun MV, Strait R. Human IgE-independent systemic anaphylaxis. J Allergy Clin Immunol 2016.

 

The Devil’s Arithmetic

When I was in grad school, I took immunology. I still have my textbook and refer to it sometimes, my crowded notes in the margins. The chapter on allergy and anaphylaxis is highlighted in green, somehow aggressively bright after eleven years.

It’s kind of amusing to recall this time in my life, before every mast cell activation pathway had been hammered into my brain. There’s also some black humor in reading about how IgE activation is the allergy pathway. You know, THE allergy pathway. This book doesn’t cover any other pathways. As if you cannot possibly be allergic to something without IgE.

That’s the problem, of course. This is what most healthcare providers or science majors learn in school. They learn about allergy and anaphylaxis, but they learn about the textbook description which invariably refers to IgE mediated food anaphylaxis. They learn about peanut allergy.

I don’t have a peanut allergy. I literally don’t have a single food allergy that displays the hallmark swelling/closing airway that people expect. But I have major food allergies, some bad enough to require epinephrine, IV Benadryl, Pepcid, Solu Medrol, Zofran and IV fluids.

The problem is not just that I’m allergic to some foods. It’s that I’m not always allergic to the same foods as I was the day before. Or the same medications. Or the same environmental exposures. My reactions on a given day are the cumulative product of the amount of irritation my mast cells have experienced in the previous day or two. There is always a running tally in my mind.

There are a lot of analogies and models used to describe mast cell attacks both to patients and to people who don’t have them. I have always thought of it as a bank. You make deposits and you make withdrawals. Like this:

For the sake of simplicity, let’s assume you have $100 in a bank account. Any activity that can cause mast cell activation has to be paid for. The cost is proportionate to the amount of activation. Getting a splinter: $2. Being hot: $10. Being in direct sunlight: $10. Standing up for 20 minutes while being hot in direct sunlight: $35. Cardiovascular exercise: $40. Arguing with your spouse: $60. Moderate pain experienced in your day to day life: $50. A painful medical procedure: $70. Mild cold: $40.

Some things are too costly to ever attempt.  Undercooked egg whites: $9000.  Massive bleach exposure: $7500.

You can make deposits into the bank with medications and physical changes. Getting enough sleep: $30. Wearing loose, comfortable clothes: $15. Doing orthostatic manuevers before standing up: $10. Taking baseline mast cell medications on your normal schedule: $50. Eating food that is warm but not hot: $15. Monitoring your exercise and stopping for breaks: $15. Wearing a cooling vest on a hot day: $20. Oral Benadryl: $25. IV Benadryl: $50. Steroids: $50.

So you have this running tally in your head all day long. When you start getting close to $100, you get stressed. You know you can’t afford to spend more than $100. Things that you could have done four hours ago safely are no longer safe. Things you could eat on a day spent relaxing at home inside with comfortable ambient temperature cannot be eaten if your apartment is too hot or if you are in a lot of pain.

You are constantly trying to avoid running out of dollars before you can get home and go to bed. Part of this is because you don’t want to trigger a physical reaction. Part of it is that this phenomenon – allergies as a function of circulating histamine/mast cell activation rather than IgE – is hard to explain briefly to people who don’t have this disease. So people will see you on a super crappy day only being able to eat one thing at a party and then four months later, when your body is much less inflamed, will see you eat three things at a party. And then it’s a thing, because these people invariably think that you are faking/being overdramatic as if somehow it is worth the effort to “pretend to have allergies.” WHO FUCKING DOES THAT?

Cost for being around someone who gives you shit for not always having the same restrictions: $75.

So everyday, you get $100. Except this is the US and our banks hate us so we have overdraft. This means that you can spend more money than you have but then they charge a steep fee and so the next day, you don’t have $100. You have maybe $30 dollars. After overspending, it can take a few days to get back to baseline.

Sometimes it’s worth it. Sometimes you can sort of game your body into getting more than $100 out of a day. This is the purpose of premedication for procedures and surgery. This is the purpose of good sleep hygiene, eating safe foods, not getting stressed, taking medications appropriately and on a schedule. You can bank a little. Not as much as you can overdraft, but you can get ahead a little bit.

Today, I went to the supermarket to grab some things for lunch at work. They didn’t have organic apples that looked in decent shape. They had non-organic apples and my safe peanut butter/honey and my safe pretzel chips. I had to run through my entire day to determine how much physical activity and stress was likely to be in the rest of my day to figure out what I could (probably) safely eat for lunch.

It’s like this all day, every day. This math wouldn’t be hard except that it’s constant and unavoidable and controls my life.

The Sex Series – Part Four: Seminal allergy

Author’s note: This series is long and covers a number of topics other than vaginally penetrating sex, including male and female orgasms, reactions of the penis, testicles and prostate, anal sex, and pelvic floor dysfunction and pelvic pain.  The first several posts are about vaginally penetrating sex because this is what I get asked the most questions about.  It is not meant to be exclusive to anyone on the basis of gender or sexual orientation.

**
It is possible to be truly allergic to semen, although this is rare.  One of the hallmarks of this condition is that it is completely preventable with condom use.

Most patients react during or after their first experience with vaginal penetration by a penis resulting in ejaculation.  Each subsequent exposure generally causes a worsening reaction. However, it is possible to develop an allergy after a number of intercourse encounters. In studies, patients with seminal allergy are allergic to semen from multiple partners, although there are anecdotes about patients reacting to semen from a single partner and not only.

This type of allergy has been linked to IgE.  The testing for this sensitivity involves skin prick tests with seminal protein that produce wheal and flare response.  Semen specific IgE is often appreciable in the blood following exposure.  Some patients have type III and type IV hypersensitivity reactions to semen and symptoms can occur days after the exposure.

Like all other forms of allergy, the range of reactions is massive.  It can range from a low level itching to anaphylaxis requiring epinephrine.  Itching, burning, redness, swelling, pain, and blistering in the vagina have all been reported. Trouble breathing, cough, wheezing, GI symptoms, generalized hives, disseminated angioedema and full anaphylaxis can occur.  Anaphylaxis has been reported in 16 cases, with one case causing loss of consciousness.

Across studies, most patients have either a personal or family history of allergic conditions.  80% of patients in one study had a family history of atopic disease.  One study found that the onset of seminal allergy often coincides with genital system conditions or procedures like hysterectomy, IUD placement or removal, pregnancy and tubal ligation.  It is hypothesized that the disruption of the normal state of immune activity in the vagina by these activities can trigger seminal allergy, but this has not been proven.

References:

Schlosser BJ. Contact dermatitis of the vulva. Dermatol Clin 2010: 28; 697-706.

Moraes PSA, Taketomi EA. Allergic vulvovaginitis. Ann Allergy Asthma Immunol 2000; 85: 253-267.

Chen WW, Baskin M. A 33-year-old woman with burning and blistering of perivaginal tissue following sexual intercourse. Annals of Allergy, Asthma & Immunology 2004; 93: 126-130.

Harlow BL, He W, Nguyen RHN. Allergic reactions and risk of vulvodynia. Ann Epidemiol 2009; 19: 771-777.

Liccardi G, et al. Intimate behavior and allergy: a narrative review. Annals of Allergy, Asthma & Immunology 2007; 99: 394-400.

Sonnex C. Genital allergy. Sex Transm Infect 2004; 80: 4-7.

How to activate mast cells: Receptors and ligands Master Table (part 1)

There are many receptors on mast cells.  The molecules that bind to these receptors are called ligands.  Different receptors can cause activation in different ways.

I am posting this table a little at a time as I anticipate getting a lot of questions about it.  I put this together for my own reference and I didn’t keep track of all sources.  I am hoping to go through the literature again and track this at some point.

These tables are not exhaustive, and I’ll add to them over time as I have the chance.

Receptor Ligand (molecules that bind to the receptor) Result
0X40 0X40 ligand Suppression of mast cell activation
A2A, A2B, A3 Adenosine At low concentration, degranulation:

histamine, tryptase, carboxypeptide, chymase, heparin, chondroitin

De novo: IL-1b, IL-3, IL-4, IL-8, IL-13

 

At high concentration, inhibits FcεRI degranulation

C3α receptor C3α De novo:
IL-3, IL-4, IL-5 IL-6, IL-8, IL-10, IL-13, TNF, GM-CSF, CCL2, CCL3, CCL5

 

Degranulation : histamine, tryptase, carboxypeptide, chymase, heparin, chondroitin

 

Increases IgE and IgG dependent degranulation

C5α receptor C5α Degranulation : histamine, tryptase, carboxypeptide, chymase, heparin, chondroitin

 

Cannabinoid CB2 receptor 2-arachidonoyl-glycerol, anandamide Suppression of mast cell activity
CCR1 CCL3 (MIP1α), CCL5 (RANTES) Degranulation : histamine, tryptase, carboxypeptide, chymase, heparin, chondroitin
CCR3 CCL11 No degranulation
Increases IgE dependent secretion: IL-3, IL-4, IL-5 IL-6, IL-8, IL-10, IL-13, TNF, GM-CSF, CCL2, CCL3, CCL5
CCR4 CCL2 (MCP-1) No degranulation, reléase of cytokines
CCR5 CCL3 (MIP1α), CCL5 (RANTES), CCL4 (MIP1β) No degranulation, reléase of cytokines
CD200 receptor CD200 (OX2) Inhibitory
Cd300α receptor Eosinophilic granule proteins Inhibitory
CD47 (integrin associated protein, IAP) Integrins Histamine secretion
CD48 E. coli, M. tuberculosis Degranulation : histamine, tryptase, carboxypeptide, chymase, heparin, chondroitin

 

De novo : TNFa, IL-6

CD72 CD100 Inhibits CKIT activation
CKIT receptor tyrosine kinase (CD117) Stem cell factor De novo:
PGD2, leukotriene B4, leukotriene C4, PAF, IL-3, IL-4, IL-5 IL-6, IL-8, IL-10, IL-13, TNF, GM-CSF, CCL2, CCL3, CCL5

 

Increased IgE dependent degranulation: histamine, tryptase, carboxypeptide, chymase, heparin, chondroitin

Corticotropin/ corticotropin releasing hormone receptor CRH, urocortin Secretion of VEGF
CX3CL1 Fractalkine No degranulation
CX3CR1 Chemokines No degranulation, reléase of cytokines
Estrogen receptor Estrogens Increased IgE dependent degranulation: histamine, tryptase, carboxypeptide, chymase, heparin, chondroitin
ETA Endothelin-1 Degranulation: Histamine, tryptase, carboxypeptide, chymase, heparin, chondroitin, renin

 

De novo: TNFa, IL-6, VEGF, TGF-b1

ETB Endothelin-1 Unknown
FcαR (CD89) IgA Unknown
FcγRIIA, FcγRI, FcγRIIIA IgG/antigen Degranulation: Histamine, tryptase, carboxypeptide, chymase, heparin, chondroitin, renin

 

De novo:
PGD2, leukotriene B4, leukotriene C4, PAF, IL-3, IL-4, IL-5 IL-6, IL-8, IL-10, IL-13, TNF, GM-CSF, CCL2, CCL3, CCL5

FcγRIIIB IgG/antigen Cannot induce activation
FcεRI IgE with or without antigen Degranulation: Histamine, tryptase, carboxypeptide, chymas, heparin, chondroitin, renin

 

De novo:
PGD2, leukotriene B4, leukotriene C4, PAF, IL-3, IL-4, IL-5 IL-6, IL-8, IL-10, IL-13, TNF, GM-CSF, CCL2, CCL3, CCL5

Regulation of mast cells by IgE and stem cell factor (SCF)

Mast cells are regulated by two dominant mechanisms. The first is the allergic response via the high affinity IgE receptor. This receptor is called FcεRI. When an IgE molecule binds to this receptor, it triggers the release of calcium in pockets inside the cells, causes the cells to take up more calcium from outside the cell, and changes the cell membrane so that it can degranulate and secrete mediators. There are a number of other things that can affect the strength of the response triggered by FcεRI.

The second mechanism is the survival and activation response when stem cell factor (SCF) binds to the CKIT receptor (also called KIT). SCF is the primary growth and survival factor in non-neoplastic mast cells. In the absence of mast cell disease, it is absolutely required for survival. SCF also attracts mast cells and enhances degranulation from the FcεRI (IgE) receptor, production of cytokines and movement of mast cells from one place to another.

When SCF is increased in tissues, it increases the amount of mast cells there, how long they live and what roles they play. It also increases mast cell responsiveness. In some instances, SCF can directly cause degranulation with IgE involvement.

Despite understanding the importance of SCF, it is not well understood what happens after SCF binds to the CKIT receptor. We know that it increases survival and proliferation, but it’s not clear how. It is possible that the concentration of SCF or CKIT may play a role.

In tissues, mast cells often exist as a part of a membrane, and SCF is important in mast cell adhesion to other cells. When SCF is part of that membrane, it can increase histamine and eotaxin production in mast cells.

Monomeric IgE is IgE that is not bound to an allergen. In the presence of SCF, monomeric IgE can directly cause release of histamine, LTC4 and IL-8. It also makes mast cells more reactive.   When monomeric IgE binds to the FcεRI (IgE) receptor without SCF present, it causes production of IL-6 but not degranulation. However, IL-6 promotes mast cell survival.

References:

Cruse, G., Bradding, P. Mast cells in airway dieases and institial lung disease. Eur J Pharmacol (2015).

River, K., Gilfillian, A.M. Molecular regulation of mast cell activation. J Allergy Clin Immunol 2006, 117, 1214-1225.

Gilfillian, A.M., Beaven, M.A. Regulation of mast cell responses in health and disease. Crit Rev Immunol 2011, 31, 475-529.

 

Mast cell inhibitory effects of some microorganisms

We have talked recently about how infections can activate mast cells and result in worsening of symptoms in mast cell patients. However, some organisms are actually able to decrease mast cell degranulation and secretion of mediators. Some of these organisms are highly pathogenic with dangerous infectious capabilities, but some are commensal bacteria that can be found in probiotics. These findings support a growing body of evidence that indicates that the changes in our commensal organisms in the last thirty years have contributed to the increased frequency of atopic disease in developed countries. Additionally, improved hygiene and public health have decreased the frequency of some infections, which may also contribute to allergic conditions.

Lactobacillus and Bifidobacteria have been found to directly inhibit mast cell degranulation. Lactobacillus reduces both mast cell degranulation and cytokine secretion by reducing the number of IgE receptors on mast cell surface. Expression of IL-8 and TNF-a are actively decreased, while expression of the anti-inflammatory IL-10 is increased. Bifidobacterium bifidum inhibit IgE activation of mast cells in similar ways.

Salmonella typhimurium is a frequent cause of foodborne illness. In the US, it is estimated to cause 1,000,000 illness events annually, resulting in 19,000 hospitalizations and 380 deaths. It causes diarrhea, fever and severe abdominal cramping that can last several days. A 2001 study found that Salmonella are able to avoid detection by neutrophils through inactivation of local mast cells. Specifically, Salmonella inject a protein known as SptP into the fluid inside mast cells. Following exposure to Salmonella, mast cells lost their ability to degranulate, even when exposed to IgE or strong antigens.

Yersinia pestis, which causes plague, can also suppress mast cell degranulation by injecting a similar protein called YopH. Several forms of commensal E. coli (which do not cause infection) have been found to exhibit similar suppression.

Some organisms can cause mast cells to lyse (burst) and thus die. Pseudomonas aeruginosa releases exotoxin A, which causes lysis of mast cells.

Infectious fungi, such as Aspergillus fumigatus, release a gliotoxin that suppresses mast cell degranulation as well as mediator secretion. Other fungal products that decrease mast cell activity include FK-506 from Streptomyces tsukubaensis and cyclosporine A from Tolypocladium inflatum. Cyclosporine A is often used as an immunosuppressive after organ transplant and also sees some use in treating inflammatory disorders.

Some nematodes (roundworms) are also able to block mast cell degranulation. Filarial nematodes release a molecule, ES-62, that blocks IgE activation of mast cells as well as inhibiting secretion of allergic inflammatory factors. This finding is notable as it provides a possible reason why allergic diseases occur less frequently in developing countries. Toxoplasma gondii, a parasitic protozoan that causes toxoplasmosis, also prevented mast cell degranulation.

 

References:

Choi, H.W., Brooking-Dixon, R., Neupane, S., Lee, C.-J., Miao, E.A., Staats, H.F., Abraham, S.N., 2013. Salmonella typhimurium impedes innate immunity with a mast-cell-suppressing protein tyrosine phosphatase, SptP. Immunity 39,1108–1120.

Cornelis, G.R., 2002. Yersinia type III secretion: send in the effectors. J. Cell Biol. 158, 401–408.

Magerl, M., Lammel, V., Siebenhaar, F., Zuberbier, T., Metz, M., Maurer, M., 2008. Non-pathogenic commensal Escherichia coli bacteria can inhibit degranulation of mast cells. Exp. Dermatol. 17, 427–435.

Harata, G., He, F., Takahashi, K., Hosono, A., Kawase, M., Kubota, A., Hiramatsu, M.,Kaminogawa, S., 2010. Bifidobacterium suppresses IgE-mediated degranulationof rat basophilic leukemia (RBL-2H3) cells. Microbiol. Immunol. 54, 54–57.

Forsythe, P., Wang, B., Khambati, I., Kunze, W.A., 2012. Systemic effects of ingested Lactobacillus rhamnosus: inhibition of mast cell membrane potassium (IKCa)current and degranulation. PLoS One 7, e41234.

Oksaharju, A., Kankainen, M., Kekkonen, R.A., Lindstedt, K.A., Kovanen, P.T., Korpela,R., Miettinen, M., 2011. Probiotic Lactobacillus rhamnosus downregulates FCER1and HRH4 expression in human mast cells. World J. Gastroenterol. 17, 750–759.

Wesolowski, J., Paumet, F., 2011. The impact of bacterial infection on mast celldegranulation. Immunol. Res. 51, 215–226.

Niide, O., Suzuki, Y., Yoshimaru, T., Inoue, T., Takayama, T., Ra, C., 2006. Fungal metabolite gliotoxin blocks mast cell activation by a calcium- and superoxide-dependent mechanism: implications for immunosuppressive activities. Clin.Immunol. 118, 108–116.

Melendez, A.J., Harnett, M.M., Pushparaj, P.N., Wong, W.S., Tay, H.K., McSharry, C.P.,Harnett, W., 2007. Inhibition of Fc epsilon RI-mediated mast cell responses by ES-62, a product of parasitic filarial nematodes. Nat. Med. 13, 1375–1381.

Hae Woong Choi, Soman N. Abraham. Mast cell mediator responses and their suppression by pathogenic and commensal microorganisms. Molecular Immunology 63 (2015) 74–79.

Allergic to infections: How bacteria, viruses and fungi activate mast cells

I am often asked about whether an infection, even a mild cold, can cause worsening mast cell symptoms.  The answer is yes.  Viral, fungal and bacterial infections can all cause mast cell activation, and patients with prior activated mast cells are especially susceptible.  This is why it is so important for mast cell patients to avoid contagious illness as much as possible.

Several cell types in the human body have Toll-like receptors (TLRs) on their cell surfaces. These receptors bind many types of molecules that indicate presence of infection. These molecules are called pathogen-associated molecular patterns (PAMPs) and they share similar shapes that identify them as being released by infecting organisms. When these PAMPs are bound by TLRs on cell surfaces, it sends signals for the cells to mount an immune response.

The expression of TLRs on mast cells has been well studied using both mouse (murine) and human mast cells. TLR1, 2, 3, 4, 5, 6, 7, 9 and 10 have been identified on mast cells by at least one study. Some of these TLRs were only detected by finding related mRNA. (When cells express a gene to make a protein like a TLR, the DNA gene is copied into mRNA, which tells the cell how to make the TLR.) Since only the mRNA and not the TLR was directly identified, these TLRs require more research to be fully characterized.

TLR2 is one of the most well studied and understood of toll-like receptors found on mast cell surfaces. TLR2 is also known as CD282. Substances that bind to TLR2 include many molecules released by bacteria and fungi. Several types of peptidoglycans and found in bacterial cell membranes bind TLR2. In particular, lipoteichoic acid is a potent activator of TLR2. This molecule is found on the surfaces of gram-positive bacteria, like Staphylococcus spp. (Staph, MRSA) and Streptococcus spp. (Strep). Other bacteria that are known to activate TLR2 include Neisseria meningitides, Haemophilus influenzae, and Borrelia burgdorferi, among others. Mycobacteria are also activating to TLR2. Zymosan is found in cell membranes of yeast and binds TLR2. Aspergillus fumigatus (fungi) and several viruses, including Herpes simplex, Varicella zoster, Cytomegalovirus and measles, activate TLR2 responses. Heat shock protein 70 (HSP 70) is released by cells in the body when they are under certain types of stress, and this can activate TLR2.

When TLR2 is bound, mast cells produce and release several types of molecules that are not prestored in granules. The molecules released depend on which protein has bound TLR2. These molecules include IL-1b, which causes inflammatory pain hypersensitivity; IL-5, which activates eosinophils; leukotriene B4, which forms reactive oxygen species and participates in inflammation; leukotriene C4, which causes slow contraction of smooth muscle, including in the airway; GM-CSF (Granulocyte macrophage colony-stimulating factor), a growth factor for white blood cells; TNF, which has many inflammatory effects; RANTES, which brings other white cells to the site of inflammation; and others. TLR2 activation is responsible for the worsening of asthma symptoms in the presence of bacterial infection.

Multiple studies reported that stimulation of TLR2 with peptidoglycan (a constituent of gram positive bacterial cell membranes) induced degranulation. Stimulation with peptidoglycan induced histamine release as well as cytokine release in a 2003 study (Varadaradjalou 2003). Another study found that peptidoglycan did not cause statistically significant degranulation, but zymosan (a fungal product) and Pam3Cys (a synthetic molecule that acts like LPS, another component of bacterial membranes) did induce significant degranulation (McCurdy 2003). Other studies have not been able to replicate these results.

There is also evidence that stimulation of TLR2 can change the behavior of mast cells. When mast cells are grown in the presence of bacterial cell membrane products, they make different amounts of different proteins. Another study demonstrated that two bacterial cell membrane products downregulated the amount of FceRI (the IgE receptor) on the surface of mast cells, so after two days, mast cells were less responsive to stimulation by IgE molecules. This was partially due to the effects of TLR2 (Yoshioka 2007).

However, mast cells that are sensitized react more strongly to TLR2 activation with LPS (Medina-Tamayo 2011). This effect seems to be reliant on prior binding of IgE. Other very technical studies have investigated the effect of antigen (such as bacterial, viral or fungal products) on the interplay between the IgE receptor and TLR receptors.   While most of this work has been done in mouse cells, several investigators have shown that activation of TLR receptors and the IgE receptor causes enhanced release of cytokines but not degranulation. It is thought that the exaggerated response to IgE receptor and TLR2 stimulation can cause the exacerbation of allergic type conditions during active infection. (Qiao 2006)

 

References:

Hilary Sandig and Silvia Bulfone-Paus. TLR signaling in mast cells: common and unique features. Front Immunol. 2012; 3: 185.

Abraham S. N, St John A. L. (2010). Mast cell-orchestrated immunity to pathogens. Nat. Rev. Immunol. 10440–452.

Dietrich N., Rohde M., Geffers R., Kroger A., Hauser H., Weiss S., Gekara N. O. (2010). Mast cells elicit proinflammatory but not type I interferon responses upon activation of TLRs by bacteria. Proc. Natl. Acad. Sci. U.S.A.1078748–8753

Gilfillan A. M., Tkaczyk C. (2006). Integrated signalling pathways for mast-cell activation. Nat. Rev. Immunol.6218–230.

Fehrenbach K., Port F., Grochowy G., Kalis C., Bessler W., Galanos C., Krystal G., Freudenberg M., Huber M. (2007). Stimulation of mast cells via FcvarepsilonR1 and TLR2: the type of ligand determines the outcome. Mol. Immunol. 442087–2094.

McCurdy,J.D., Olynych,T.J., Maher, L. H.,and Marshall, J.S.(2003). Cutting edge: distinct Toll-like receptor2 activators selectively induce different classes of mediator production from human mast cells. J. Immunol. 170, 1625–1629.

Medina-Tamayo, J., Ibarra-Sanchez, A., Padilla-Trejo,A., and Gonzalez- Espinosa, C. (2011). IgE-dependent sensitization increases responsiveness to LPS but does not modify development of endotoxin tolerance in mast cells. Inflamm. Res. 60, 19–27.

Qiao,H., Andrade,M.V., Lisboa,F. A., Morgan,K., and Beaven, M. A. (2006).FcepsilonR1 and toll-like receptors mediate synergistic signals to markedly augment production of inflammatory cytokines in murine mast cells. Blood 107, 610–618.

Yoshioka,M., Fukuishi,N., Iriguchi,S., Ohsaki, K., Yamanobe,H., Inukai, A., Kurihara,D., Imajo,N., Yasui, Y., Matsui, N., Tsujita, T., Ishii, A., Seya,T., Takahama,M., and Akagi, M. (2007). Lipoteichoicacid down- regulates FcepsilonRI expressionon human mast cells through Toll-like receptor2. J. Allergy Clin. Immunol. 120, 452–461.

Varadaradjalou, S., Feger, F., Thieblemont, N., Hamouda, N.B., Pleau, J. M., Dy,M., and Arock, M. (2003). Toll-likereceptor2 (TLR2)and TLR4 differentially activate human mast cells. Eur. J. Immunol. 33, 899–906.

Food allergy series: FPIES (part 2)

FPIES is usually diagnosed clinically. Endoscopy and biopsy are not necessary to diagnose, but is sometimes done to rule out other conditions.

Scopes have shown a variety of inflammatory changes in the GI tract of FPIES kids. Diffuse colitis, friable mucosa, rectal ulceration and bleeding have been observed.  Increased levels of TNFa and decreased receptors for TGF-b have been found in the GI tract. Baseline intestinal absorption is usually normal.

Biopsies have shown villous atrophy, tissue edema, crypt abscesses, increased white blood cells, including eosinophils and mast cells, and IgM and IgA containing plasma cells. Radiology showed air fluid levels (collection of both fluid and gas in the intestines), narrowing and thickening of the mucosa in the rectum and sigmoid colon and thickening of the circular folds in the small intestine. When surgery has been performed, distension of the small bowel and thickening of the jejunum has been seen.

Food specific IgE is not usually present. In one study, 21% of patients with solid food FPIES had detectable food specific IgE. 18-30% with FPIES to cow’s milk or soy have IgE for it. If IgE is found, the course of FPIES is longer. One study found a decrease in food specific IgG4 in FPIES patients along with an increase in food specific IgA.

FPIES is managed by removing the offending food. Exclusive breastfeeding can be protective. If not breastfed, use of casein hydrolysate formula is recommended. Less commonly, amino acid formula or IV fluids may be needed. Doctors recommend introducing yellow vegetables and fruits as solids rather than cereal at six months of age. Grains, legumes and poultry should be avoided for the first year of life. Once tolerance is established to one food in a high risk category, like grains, the child is more likely to tolerate other foods in the same category.

Oral food challenges (OFC) should be undertaken to determine if tolerance to the food has been achieved. A conservative approach recommends challenges every 18-24 months in patients without recent symptoms. OFCs are high risk procedures for FPIES children. The following procedure should be observed:

  • Any FPIES OFC must be physician supervised. Generally, inpatient settings are preferred, but if an outpatient setting can provide appropriate supportive care, it may be acceptable. Intravenous access should be secured prior to beginning and IV fluids and medications should be immediately available in case of reaction. ICU care is not recommended unless there is a history of near fatal reactions.
  • Blood should be drawn immediately before beginning the OFC to provide baseline complete count count and neutrophil count.
  • Over the first hour, 0.06-0.6g/kg body weight of food protein should be administered in three equal doses. It should not exceed 3g of total protein or 10g of total food or 100ml of liquid for initial feeding.
  • If patient has no reaction, give a full serving of food as determined by their age.
  • Observe patient for several hours afterward.
  • In the event of reaction, administer 20 ml/kg boluses of normal saline.
  • In the event of severe reaction, including repetitive vomiting, profuse diarrhea, lethargy, hypotension or hypothermia, administer 1 mg/kg methylprednisolone intravenously, up to 60-80mg total. About 50% of patients who react to FPIES OFCs will need IV fluids and steroids.
  • Epinephrine must be available during FPIES OFCs for treatment of hypotension and shock. In FPIES cases, epinephrine does not resolve vomiting and lethargy.
  • In children with positive skin tests and/or food specific IgE, antihistamines should also be available during OFCs.
  • Blood should be drawn six hours after OFC to compare to baseline values. If patient has diarrhea, stool guaiac tests should be done, and stool samples should be tested for white bloods, red blood cells and eosinophils in feces.

An OFC is considered either positive or negative. Positive means there is a reaction. Negative means there is not. It is positive if the patient experiences vomiting, lethargy or diarrhea in an appropriate time frame. In the absence of symptoms, if the neutrophil count is over 3500/ul, or white blood cells, frank or occult blood, and/or eosinophils are present in feces, the challenge is still considered positive.  More than 10 leukocytes/hpf in gastric juice at the 3 hour mark has been suggested as a positive marker, but needs further investigation. In the study that noted this marker, gastric juice was obtained via orogastric feeding tubes.

One study looked at the resolution of FPIES over a ten year period. 160 subjects were included in the study. 54% were male. Median age of diagnosis was 15 months. 180 OFCs were done for 82 patients, of which 30% had obtained an FPIES diagnosis based on previous OFCs. 44% of patients reacted to cow’s milk; 41% to soy; 22.5% to rice; and 16% to oat. 65% had only one food sensitivity, 26% had two, and 9% had three or more. Most had some form of atopic disease and 39% had detectable food specific IgE. 24% had IgE specific for the food causative for their FPIES reaction. Of the patients with IgE for cow’s milk, 41% of them moved from an FPIES reaction type to an IgE allergy reaction type.

60% of FPIES cases resolve by three years of age. This finding is an average and different populations see much different results. In South Korea, 90% of patients resolve by three years of age. In the US, only 25% resolve by this age. The differences observed are thought to be due to other factors, such as the frequency of food specific IgE and atopic disease. The median age for FPIES resolution depended largely on the food: 4.7 years for rice, 4 years for oat, 6.7 years for soy, 5.1 years for milk. If milk IgE was present, the patient did not become tolerant of milk during the course of study.

FPIES overwhelmingly affects very young children. However, there are rare cases of older children and adults developing FPIES at a later age. These cases involve fish and shellfish as the offending foods.

 

References:

Leonard, Stephanie, Nowak-Wegrzyn, Anna. Food protein induced enterocolitis syndrome: an update on natural history and review of management. Ann Allergy Asthma Immunol. 2011; 107:95-101.

Caubet, Jean Christoph, et al. Clinical features and resolution of food protein induced enterocolitis syndrome : 10-year experience. J Allergy Clin Immunol. 2014; 134(2): 382-389.