HYPERSENSITIVITY REACTIONS

HYPERSENSITIVITY REACTIONS 

 Refers to excessive, undesirable reactions produced by the normal immune system. 

Four types: type I, type II, type III and type IV.

Type I:

immediate or anaphylactic hypersensitivity.

:mediated by  IgE.

The reaction may involve skin,eye, nasopharynx , bronchopulmonary tissues ,gastrointestinal tract.

 The primary cellular component is the mast cell or basophil. 

The reaction is modified by platelets, neutrophils and eosinophils.(mainly mast cells and eosinophils)

The mechanism of reaction:produce IgE, in response to certain allergens.

Reason: individuals produce more of TH2 cells that secrete IL-4, IL-5 and IL-13 which in turn favor IgE class switch. IgE has very high affinity for its receptor (Fcε; CD23) on mast cells and basophils.

A subsequent exposure to the same allergen cross links the cell-bound IgE and triggers the release of various pharmacologically active substances . Cross-linking of IgE Fc-receptor is important in mast cell triggering. Mast cell degranulation is preceded by increased Ca++ influx, which is a crucial process; ionophores which increase cytoplasmic Ca⁺⁺also promote degranulation.

I think I have a type 1 hypersensitivity, because when I eggplant, tomato sauce, pepper , all of my body is itching.