Type lll Hypersensitivity reaction
(Immune complex sensitivity)
Type lll HS reaction is mediated by IgM or IgG.
These complexes may be deposited at different sites in the body such as; kidney, joint, skin and eye.
Phagocytosis take place or chemical substance are released by damaged cells where Ag-Ab (antigen- antibody complex) takes place.
For example;
1. Serum sickness
Horse serum used to provide Immunity against diphtheria toxin.
Horse's seum contains antibodies to the diphtheria toxin but horse serum is recognised as foreign (non- self) in human.
That's why immune system react against it.
If second dose of serum given, serum sickness occurs in body.
Symptoms of serum sickness fever, enlarged lymph nodes and spleen, arthritis, inflammation of kidney, heart and blood vessels, rashes and abdominal pain, due to Ag- Ab complex formed in these organ.
Anaphylatic (immediate reaction) type of Hypersensitivity
It includes; Direct skin test for allergens.
Technique;
1. Prausnitz - kustner reaction
2. Penicillin hypersensitivity
3. Foshay's test
4. Extract of parasitic worms
Patient is normally tested either with the scratch or intradermal method for sensitivity to a variety of allergens.
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