| TYPE |
DESCRIPTIVE |
INITIATION |
MECHANISM |
EXAMPLES |
| |
NAME |
TIME |
|
|
| I |
IgE-mediated hypersensitivity |
2-30 mins |
Ag induces cross-linking of IgE
bound to mast cells with release of vasoactive mediators |
Systemic anaphylaxis, Local
anaphylaxis, Hay fever, Asthma, Eczema |
| II |
Antibody-mediated cytotoxic
hypersensitivity |
5-8hrs |
Ab directed against cell-surface
antigens mediates cell destruction via ADCC or complement |
Blood transfusion reactions,
Haemolytic disease of the newborn, Autoimmune Haemolytic anaemia |
| III |
Immune-complex mediated
hypersensitivity |
2-8hrs |
Ag-Ab complexes deposited at various
sites induces mast cell degranulation via FcgammaRIII, PMN
degranulation damages tissue |
Arthus reaction (Localised);
Systemic reactions disseminated rash, arthritis,
glomerulonephritis |
| IV |
cell-mediated hypersensitivity |
24-72hrs |
Memory TH1 cells release cytokines
that recruit and activate macrophages |
Contact dermatitis, Tubercular
lesions |