8.
“The immune system is an incredibly complex and nuanced organization of cells that communicates readily to destroy anything deemed hostile within the body. It helps explain why vaccines are supposed to work, why allergies come and go, and why transfusions/transplants are hard to successfully pull off.”
“Here is a brief explanation of how allergies work, using pollen (allergic rhinitis) as an example:
Your immune system senses pollen in the body. It doesn’t appear to be one of your cells, so the B-cell collects samples of it, relays it to a Helper T-cell, which in turn helps specialize the B-cell to become one of two cells: effector and memory cells. Effectors mass produce antibodies, while memory cells are reserved for future invasions (this is why initial exposure to a new substance may not necessarily trigger allergic responses. The signal is still weak as the immune system is still acclimating to a foreign particle). Antibodies flood the pollen particles and signal for basophils/mast cells to release histamine, the hormone responsible for inflammatory responses. This is where the runny noses and sneezing come into play (and for more severe allergies, anaphylatic shock).
Allergies may fade out over time for several reasons. When exposed to a non-threatening level of an allergy for a long enough time, the body decides that it’s not really a threat anymore. Furthermore, as people age, the immune system weakens, making it harder to detect and overreact to allergies.”
—u/Dasians
