Type –III hypersensitivity / Immune-complex hypersensitivity at a glance

Type –III hypersensitivity is mediated by immune complxes , theat is antigen- antibody  complexes. This immune complex may be formed within the circulation or locally at a site.

Pathogenesis:

• ·                     Formation of antigen- antibody  complexes
• ·                     Deposition of immune complxes in various tissue
• ·                     Initiation of inflammatory reaction in dispersed site by releasing C3a and C5a

Examples:

A. Systemic immune complex Diseases

• ·         Serum sickness
• ·         Immune complex glomerulonephrities (by Streptococcus pyogenes antigen,staphylococcus aureus antigen , Treponema pallidum antigen , Schistosoma spp ,hepatitis B; hepatitis C virus antigen  ,Epstein-barr,measles,mumps viruses, malignant tumor antigen etc )
• ·         Systemic lupus erythematosus
• ·         Immune complex vasculitis
• ·         Dengue haemorrhagic fever
• ·         Dengue shock syndrome
• ·         Drugs : penicillin etc

B. Systemic immune complex Diseases

• ·         Arthus reaction
• ·         Rheumatoid arthritis (Yersinia enterocolitica antigen etc )

• ·         Extrinsic allergic alveolitis / Farmer’s lung

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