I have answered the 107 questions I have been asked most in the last four years. No jargon. No terminology. Just answers.
24. What is degranulation?
• Mast cells make chemicals inside them and often store them in pockets inside themselves. These pockets are called granules. When mast cells turn these pockets out so that the chemicals are dumped out of them into the body, that is called degranulation.
• There are several ways that mast cells release chemicals. These chemicals are commonly called mediators because they mediate many reactions in the body.
• Mast cells have to find certain building blocks from inside the body and whenever they find them, they use them to make mediators they need. Mast cells make some mediators whenever they have the opportunity and save them for later so they are there when they are needed. Often, the way mast cells save these mediators is by placing them inside granules. Mediators that are kept this way are called stored mediators.
• Mast cells have two options for getting those mediators out of their granules into the body. The first is to empty some of the granules entirely, just push everything out into the body at once. They can also release a little at a time. When mast cells are activated in response to an allergic or infectious process, overwhelmingly, they release the contents of a granule all at once.
• Frequently, they empty many of the granules at the same time. This can cause an emergency response in your body and can impact your entire body. This is what happens during anaphylaxis but it happens during other processes too, like mast cell attacks, bad infections, or sudden trauma.
• When mast cell patients say “I am degranulating”, it means they feel symptoms associated with mast cell mediator release. Histamine is stored in granules in large quantities so this is an offhand way of saying that they are feeling symptoms coming on.
• Mast cells have other ways of releasing mediators. They make some mediators only when they need to use them. These mediators are not stored but the building blocks they need are. A good example of this method is prostaglandin D2.
• Mast cells do not make prostaglandin D2 and stuff it inside granules. Instead, they keep the building blocks to make it inside of themselves. In this case, the building block they store is called arachidonic acid. When mast cells need to make prostaglandin D2, they use some of the arachidonic acid they have stored. But as soon as they use it to make prostaglandin D2, the mast cells secrete it right into the body. It is not stored in a granule.
• Mediators that are made with this kind of process are called “de novo” mediators. This means that the mediators are made “new” on demand when they are needed.