Anaphylaxis comes from the greek word “ana-“ which roughly means against and “phylaxis” which means protection, implying that someone’s immune system has reacted to something in such a way that ends up damaging them, instead of protecting them.
It’s basically a severe type of allergic reaction that affects multiple organ systems and it’s potentially life-threatening.
Normally, the immune system recognizes and acts against pathogens that can cause disease.
These pathogens have specific molecules on their surface, called antigens, and they help trigger an immune response.
In some individuals, though, the immune system overreacts and starts targeting harmless molecules that don’t cause any problems for most people.
These include molecules found in foods like peanuts and shellfish, medications like antibiotics, and in the venom of insect bites.
In most cases, there might be a mild to moderate allergy, but sometimes things get really serious, involving two or more organ systems, and at that point it’s called anaphylaxis.
Anaphylaxis, just like any allergic response, happens in two steps, a first exposure, or sensitization, and then a subsequent exposure, which is when it actually gets a lot worse.
So, let’s say a person is stung by a bee from a nearby beehive, for the first time in their life.
When the bee pierces the skin with its stinger, its venom gets into the skin.
Part of that venom molecule can get picked up by a dendritic cell, which is a type of immune cell.
The dendritic cell gobbles up the foreign particle and presents it to a nearby lymphocyte, called a T cell.
If the T cell is activated, it starts to produce cytokines, which stimulate B cells, another group of lymphocytes, which produce IgE antibodies.
These IgE antibodies get released into the bloodstream and bind to the surface of mast cells and basophils, which are immune cells that are full of granules that contain proinflammatory molecules.