Type IV hypersensitivity

Type IV hypersensitivity
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 that 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, whereas activated macrophages produce hydrolytic enzymes and, on presentation with certain intracellular pathogens, transform into multinucleated giant cells.

Examples

Disease Target antigen Effects
Diabetes mellitus type 1 Pancreatic beta cell proteins
(possibly insulin, Glutamate decarboxylase)
Multiple sclerosis Oligodendrocyte proteins
(myelin basic protein, proteolipid protein)
Rheumatoid arthritis 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
Contact dermatitis Environmental chemicals, e.g. poison ivy, nickel
Mantoux test* (diagnostic) Tuberculin
Unless else specified in boxes, then ref is: [1]

* - Mantoux test not taken from [1]

The pathophysiology of the Tuberculin reaction is explained thus: M. tuberculi are engulfed by macrophages after being identified as foreign, but due to a self- preserving mechanism peculiar to TB it is able to block the fusion of the phagosome within which it is existing with the lysosome which would destroy it. So it can continue existing and replicating within the immune cell designed to destroy it. After several weeks, the immune system somehow [ mechanism as yet unexplained] ramps up and, on stimulation with IFN-gamma, the macrophages become capable of killing M. tuberculi by forming phagolysosomes and nitric oxide radicals. However unfortunately the hyper-activated macrophages secrete TNF which recruits multiple monocytes into the battle. These cells differentiate into epithelioid histiocytes which wall off the infected cells, but at the cost of significant inflammation and local damage.

Some other clinical examples:

References

  1. ^ a b Table 5-5 in: Mitchell, Richard Sheppard; Kumar, Vinay; Abbas, Abul K.; Fausto, Nelson. Robbins Basic Pathology. Philadelphia: Saunders. ISBN 1-4160-2973-7.  8th edition.
  2. ^ "eMedicine - Hypersensitivity Reactions, Delayed : Article by Walter Duane Hinshaw". http://www.emedicine.com/MED/topic1100.htm. 

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Look at other dictionaries:

  • type IV hypersensitivity — hypersensitivity initiated by antigen specific T lymphocytes; unlike forms mediated by antibodies, it takes one or more days to develop and can be transferred by lymphocytes but not by serum. The term is often equated with delayed… …   Medical dictionary

  • type I hypersensitivity — hypersensitivity that occurs rapidly (within several minutes) upon reexposure to an antigen, due to interaction of IgE and the antigen; see type I hypersensitivity reaction, under hypersensitivity reaction, at reaction …   Medical dictionary

  • type II hypersensitivity — hypersensitivity resulting from antibody antigen interactions on cell surfaces; see type II hypersensitivity reaction, under hypersensitivity reaction, at reaction. Called also antibody mediated h …   Medical dictionary

  • type III hypersensitivity — hypersensitivity due to formation of circulating antigen antibody complexes and their deposition in tissues; see type III hypersensitivity reaction, under hypersensitivity reaction, at reaction. Called also immune complex–mediated h …   Medical dictionary

  • Type I hypersensitivity — Infobox Disease Name = Type I hypersensitivity Caption = SEM of miscellaneous plant pollens. Pollens are very common allergens. DiseasesDB = ICD10 = ICD9 = ICDO = OMIM = MedlinePlus = eMedicineSubj = eMedicineTopic = MeshID = D006969 Type I… …   Wikipedia

  • Type III hypersensitivity — Infobox Disease Name = PAGENAME Caption = DiseasesDB = ICD10 = ICD9 = ICDO = OMIM = MedlinePlus = eMedicineSubj = eMedicineTopic = MeshID = D007105 Type III hypersensitivity occurs when antigens and antibodies are present in roughly equal amounts …   Wikipedia

  • Type II hypersensitivity — In type II hypersensitivity (or cytotoxic hypersensitivity)cite web |url=http://pathmicro.med.sc.edu/ghaffar/hyper00.htm |title=Hypersensitivity reactions |format= |work= |accessdate=] the antibodies produced by the immune response bind to… …   Wikipedia

  • type IV hypersensitivity — A delayed hypersensitivity response (it appears 24 to 48 hours after antigen exposure). It results from the binding of antigen to activated T lymphocytes, which then release cytokines and trigger inflammation and macrophage attacks that damage… …   Dictionary of microbiology

  • Type V hypersensitivity reaction — A Type V hypersensitivity reaction occurs when IgG class antibodies directed towards cell surface antigens have a stimulating effect on their target.Grave s disease is an example of this type of hypersensitivity reaction. This disease is also… …   Wikipedia

  • type I hypersensitivity — A form of immediate hypersensitivity arising from the binding of antigen to IgE attached to mast cells, which then release anaphylaxis mediators such as histamine. Examples: hay fever, asthma, and food allergies …   Dictionary of microbiology

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