Allergic Reactions Occur Only in People Who Are Sensitized by Prior

question 24

Multiple Choice

Allergic reactions occur only in people who are sensitized by prior exposure to a specific allergen. Please identify the correct sequence of events that occur in a type I response.
1) The activated B cells proliferate into IgE-producing plasma cells and memory cells.
2)  The Fc portion of the IgE binds to Fc receptors on either mast cells or basophils, so that the Fab sites of the antibodies can interact with a specific allergen.
3)  Sensitization begins when the first contact with the allergen induces an antibody response-helper T cells activate naive B cells.
4) Cross-linking triggers the mast cell  or basophil to undergo degranulation, a process that releases its inflammatory mediators.
5) On second exposure to the antigen, when adjacent IgE molecules on a mast cell or basophil bind to that antigen, the IgE molecules are cross-linked.
6)  These inflammatory mediators can have a variety of effects associated with a type I allergy response. 

• A) 3, 4, 1, 2, 5, 6
• B) 2, 3, 1, 4, 6, 5
• C) 6, 4, 3, 2, 5, 1
• D) 3, 1, 2, 5, 4, 6
• E) 3, 1, 6, 5, 2, 4

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