My confusion with IgE antibodies and allergy?

[sameeralord]

Hello everyone,

There was a simple question given, where there was a bee sting on a guy and the question asked was what is the antibody involved. The answer is IgE. Now my question is when there is bee sting for the first time, why do we called it an allergic reaction. I mean for an allergy to occur don't we have to be exposed to the antigen second time, so IgE attached to Mast cells will release histamine 2nd time. Also why aren't other antibodies like IgA ect not involed in a bee sting. Thanks :smile:

[Jack the Stri]

You are correct, the allergic reaction only occurs after the second sting and due to presence of IgE antibodies. IgA is not involved in this because it functions in mucosal immunity.

[sameeralord]

You are correct, the allergic reaction only occurs after the second sting and due to presence of IgE antibodies. IgA is not involved in this because it functions in mucosal immunity.

Hey thanks for help Jack :smile: I have a quick clarification though. IgA protects body surfaces. It is synthesized by secretory epithelial cells. So it should be found in skin. Is the reason it is not involved is because it protects against microorganisms and IgE against allergens.

[bobze]

Hey thanks for help Jack :smile: I have a quick clarification though. IgA protects body surfaces. It is synthesized by secretory epithelial cells. So it should be found in skin. Is the reason it is not involved is because it protects against microorganisms and IgE against allergens.

Yea kind of. Remember that immunoglobulins are 3d things that bind to different stuff. IgE mostly has impacts on mast cells and basophils and incite them to release their granules (degranulation). Mast cells and basophils contain granules with histamine and heprain (probably the two most important components anyway) which cause "allergic" reactions.

Specifically in the respiratory system (which just make matters confusing for you, the respiratory system has opposite reactions of the systemic parts of the body) histamine causes vasoconstriction. Which makes sense if you think about it from your bodies point of view. If you are breathing "something bad" the body wants to restrict the air inflow to those parts of the tracheobronchial tree, restricting intake of the irritant. The problem occurs when too much histamine is released and you have global (relative to the lung) vasoconstriction which restricts total air flow. In the systemic parts of the body (the nose for instance), histamine causes vasodialation and increased secretions. Again, makes sense from your body's POV. If you have a pathogen invading the nose, you want more blood flow (increases the availability of leukocytes) and more mucous to "flush" the pathogen out.

Secretory IgA (~10% of our IgA) is produced by plasma cells which constitutively secrete IgA which is then transported across the mucosal epithelium and out of the body (via bodily secretions) and mostly aids in interference of bacterial pathogenesis or assists in opsonization (searchable term) of pathogens.