Biology, Eighth Edition (Raven)

Chapter 51: The Immune System

IgE Mediated (Type 1) Hypersensitivity

How do allergies develop? Allergies are exaggerated and inappropriate immune responses caused by B cells producing excess IgE antibodies. An allergen is a foreign substance, often food, pollen, dust (small fragments of organic material), or a chemical such as an antibiotic. The allergen binds to the antibodies and triggers a reaction that includes the production of histamine. The effect is usually local, as in hay fever, but in some cases the whole body can be affected with very serious health consequences. Histamines can cause a dramatic drop in blood pressure and lead to anaphylactic shock. The reasons for the development of allergies are unclear. It is possible that they are a side effect of evolved immune responses to eukaryotic parasites such as nematode worms. Allergies can develop at any time and can become more or less severe with age.

View the animation below, then complete the quiz to test your knowledge of the concept.


In IgE mediated hypersensitivity, all of the following are needed except
A)antigen presenting cell
B)B cell
C)IgE antibody
D)mast cell

IgE molecules attach to
A)mast cells via their variable region
B)mast cells by their constant region
C)T helper cells by their variable region
D)plasma cells by their constant region

Histamine released by mast cells leads to all of the following symptoms except
A)capillary dilation
B)airway constriction
C)high fever
D)mucus secretion

For a hypersensitivity response to occur, two bound IgE molecules on a mast cell must react with a specific antigen.

Activated T helper cells produce cytokines, which stimulate B cells to proliferate and differentiate into plasma cells capable of producing IgE.
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