How to activate mast cells: Complement protein C3a
- The complement system is part of the immune system. It allows infecting organisms to be more readily found and destroyed by the immune system.
- Mast cells express a receptor for C3a, a fragment produced during activation of the immune system.
- C3a is an anaphylatoxin. It participates in exaggerating the anaphylactic response.
- C3a increases vascular permeability, causes smooth muscle contraction, and draws white blood cells to inflamed spaces.
- In mucosal mast cells (GI mucosa), C3a inhibits histamine and TNF release.
- In serosal mast cells (skin, peritoneum, respiratory tract), C3a induces degranulation when stimulated by IgE or IgG.
- Inhaled allergens activate complement system in mucosa of respiratory tract, resulting in formation of C3a.
- Tryptase can change C3 to C3a.
Corticotropin releasing hormone, cortisol and mast cells
- The term HPA axis refers to the mechanisms by which the hypothalamus, pituitary gland and adrenal glands control each other.
- The HPA axis regulates many things, including the stress response, immune modulation, emotions, sexuality and digestion.
- The hypothalamus is in the brain. It turns signals from the nervous system into endocrine signals that allow changes by using hormones.
- The hypothalamus makes corticotropin releasing hormone (CRH).
- The pituitary gland makes and releases many hormones, including adrenocorticotropic hormone (ACTH), thyroid stimulating hormone, growth hormone and others.
- When the pituitary gland receives signals from the hypothalamus, it releases these hormones.
- CRH from the hypothalamus stimulates the pituitary to produce ACTH.
- The adrenal glands make and release cortisol, epinephrine, norepinephrine and other molecules in response to hormones from the pituitary.
- ACTH from the pituitary stimulates the adrenals to produce cortisol.
- Cortisol tells the hypothalamus to stop releasing CRH and the pituitary to stop making ACTH.
- Taking steroids regularly suppresses ACTH so your body stops making its own steroids. This is weaning steroids is important.
- CRH is released in response to stress, such as anaphylaxis.
- CRH can bind to mast cells and cause release of VEGF.
- CRH is also released by mast cells.