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Type III hypersensitivity
Classification and external resources

Immune complex
MeSH D007105
Hypersensitivity types
Type I - Allergy (immediate)
Type II - Cytotoxic, antibody-dependent
Type III - Immune complex disease
Type IV - Delayed-type hypersensitivity
(Antibody Independant)
Type V - Autoimmune disease

Type III hypersensitivity occurs when antigens and antibodies (IgG or IgM) [1] are present in roughly equal amounts, causing extensive cross-linking.

Presentation

It is characterized by soluble antigens that are not bound to cell surfaces (which is the case in type II hypersensitivity). When these antigens bind antibodies, immune complexes of different sizes form[2 ]. Large complexes can be cleared by macrophages but they have difficulty binding to small immune complexes for clearance. These immune complexes insert themselves into small blood vessels, joints, and glomeruli, causing symptoms.

They deposit in tissues and induce an inflammatory response,[3] and can cause damage wherever they precipitate.

The reaction can take hours, days, or even weeks to develop.

Examples

Some clinical examples:

Disease Target antigen Main effects
Systemic lupus erythematosus Nuclear antigens
Post-streptococcal glomerulonephritis Streptococcal cell wall antigens
  • Nephritis
Polyarteritis nodosa Hepatitis B virus antigen
Reactive arthritis Several bacterial antigens
  • Acute arthritis
Serum sickness Various
  • Arthritis
  • Vasculitis
  • Nephritis
Arthus reaction Various
  • Cutaneous vasculitis
Unless else specified in boxes, then ref is: [4]

Other examples are:

References

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