Type ll Hypersensitivity Reaction (Cytotoxic and Cytolytic)
It is mediated by antibodies (IgG, IgM).
When antigen binds to cell surface, these antibodies lead to toxicity (cytotoxicity) or cytolysis (brusting of cells).
The antibody is proceeded against an antigen that can be microbial product absorbed on to a cell or drug.
Both IgG and IgM are produced in type ll reaction.
For example;
1. In case of autoimmune anemia and hemolytic diseases of new born, lysis of RBC's take place by anti RBC's antibodies.
The allergen on the cell surface reacts with antibody to form a complex.
Complement proteins bind with complex and cause lysis of target cell or encourage phagocytosis.
2. Drug reaction
Certain drugs (penicillin, phenacetin) when ingested, get attached to the cell membranes of red cells, neutrophils or platelets and initiated Ab formation. Combination of Ag and Ab lead to cytotoxic (damaging cell) or cytolytic (hemolytic) reaction.
3. Bacterial reaction
These reactions are observed in infections like salmonella and mycobacterium infection.
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