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 IV hypersensitivity
Classification and external resources
MeSH	D006968

Type IV hypersensitivity is often called delayed type hypersensitivity as the reaction takes two to three days to develop. Unlike the other types, it is not antibody mediated but rather is a type of cell-mediated response.

CD8+ cytotoxic T cells and CD4+ helper T cells recognize antigen in a complex with either type 1 or 2 major histocompatibility complex. The antigen-presenting cells in this case are macrophages which secrete IL-12, which stimulates the proliferation of further CD4+ T cells. CD4+ T cells secrete IL-2 and interferon gamma, further inducing the release of other Type 1 cytokines, thus mediating the immune response. Activated CD8+ T cells destroy target cells on contact while activated macrophages produce hydrolytic enzymes and, on presentation with certain intracellular pathogens, transform into multinucleated giant cells.

[edit] Examples

Disease	Target antigen	Effects
Diabetes mellitus type 1	Pancreatic beta cell proteins (possibly insulin, Glutamate decarboxylase)	Insulitis Beta cell destruction
Multiple sclerosis	Oligodendrocyte proteins (myelin basic protein, proteolipid protein)	Demyelinating disease Perivascular inflammation Paralysis Ocular lesions
Rheumatoid arthritis - Type III Hypersensitivity	Antigen in synovial membrane (possibly type II collagen)	Chronic arthritis Destruction of articular cartilage and bone
Some Peripheral neuropathies	Schwann cell antigen	Neuritis Paralysis
Crohn's disease	Unknown	Chronic inflammation of ileum and colon
Contact dermatitis	Environmental chemicals, e.g. poison ivy	Dermatitis with usually short-lived itching
Mantoux test* (diagnostic)	Tuberculin	Skin induration indicates TB exposure
Unless else specified in boxes, then ref is: [1] * - Mantoux test not taken from [1]

Some other clinical examples:

• Temporal arteritis
• Hashimoto's thyroiditis
• Symptoms of leprosy
• Symptoms of tuberculosis
• Coeliac disease
• Graft-versus-host disease^[2]
• Chronic transplant rejection

[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