PHGY 313 Lecture Notes - Lecture 19: Type I Hypersensitivity, T Helper Cell, Type Iv Hypersensitivity

• School: McGill University
• Department: Physiology
• Course: PHGY 313
• Professor: Kathleen Cullen

Document Summary

4 types of hypersensitivity: o o o o o o o o o o o o o: type 1. Antigen: cell or matrix-associated antigen, cell surface receptor. Mechanism: complement, phagocytes, nk cells, antibody alters signaling: type 3. Reduced exposure to pathogens in developed world can promote allergic disease (atopy) Reciprocal balance between th1 and th2 responses (low th1 activation atopic. In sanitary developed countries, there isn"t much of these pathogens so low th1 activation. Inherited and environmental factors are determinants of atopic allergic diseases (ige-mediated type 1) Exposure to infectious agents in childhood stimulates a th1 type of immune response and non-atopy. Diet, microbiota, genetics are other factors that lead to atopy. Prerequisite for type 1 hypersensitivity reaction is: production of ige during 1st o encounter with ag. Ige binds irreversibly to fc receptors on mast cells, basophils, and eosinophils. Ige causes allergic reactions due to high affinity fc receptor and cell distribution of the receptor (fc r)