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.

[edit] 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.

[edit] Examples

Some clinical examples:

Disease	Target antigen	Main effects
Systemic lupus erythematosus	Nuclear antigens	Nephritis Skin lesions Arthritis
Post-streptococcal glomerulonephritis	Streptococcal cell wall antigens	Nephritis
Polyarteritis nodosa	Hepatitis B virus antigen	Systemic vasculitis
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:

• Rheumatoid arthritis
• Subacute bacterial endocarditis^[5]
• Symptoms of malaria
• Farmer's lung (Arthus-type reaction)

[edit] References

v • d • e Immune disorders: hypersensitivity and autoimmune diseases Type I/allergy/atopy (IgE) Foreign Atopic dermatitis · Allergic urticaria · Hay fever · Allergic asthma · Anaphylaxis · Food allergy (Milk, Egg, Peanut, Tree nut, Seafood, Soy, Wheat), Penicillin allergy Autoimmune none Type II/ADCC (IgM, IgG) Foreign Pernicious anemia · Hemolytic disease of the newborn Autoimmune Cytotoxic Autoimmune hemolytic anemia · Idiopathic thrombocytopenic purpura  · Bullous pemphigoid  · Pemphigus vulgaris · Rheumatic fever · Goodpasture's syndrome "Type 5"/receptor Graves' disease · Myasthenia gravis Type III (Immune complex) Foreign Henoch-Schönlein purpura · Hypersensitivity vasculitis · Reactive arthritis · Rheumatoid arthritis · Farmer's lung · Post-streptococcal glomerulonephritis · Serum sickness · Arthus reaction Autoimmune Systemic lupus erythematosus · Subacute bacterial endocarditis Type IV/cell-mediated (T-cells) Foreign Contact dermatitis · Mantoux test Autoimmune Diabetes mellitus type 1 · Hashimoto's thyroiditis · Guillain–Barré syndrome  · Multiple sclerosis  · Coeliac disease · Giant cell arteritis GVHD Transfusion-associated graft versus host disease Unknown/ multiple Foreign Hypersensitivity pneumonitis (Allergic bronchopulmonary aspergillosis) · Transplant rejection · Latex allergy (I+IV) Autoimmune Sjögren's syndrome · Autoimmune hepatitis · Autoimmune polyendocrine syndrome (APS1, APS2) · Autoimmune adrenalitis lymphocyte navs: cells/physio, immunodeficiency/immunoproliferative immunoglobulin/neoplasia, proc