cytotoxic hypersensitivity

hypersensitivity /hy·per·sen·si·tiv·i·ty/ (-sen″sĭ-tiv´ĭ-te) a state of altered reactivity in which the body reacts with an exaggerated immune response to what is perceived as a foreign substance. The hypersensitivity states and resulting reactions are usually subclassified by the Gell and Coombs classification (q.v.).hypersen´sitive

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antibody-mediated hypersensitivity 

1. type II h.; see Gell and Coombs classification, under classification.

2. occasionally, any form of hypersensitivity in which antibodies, rather than T lymphocytes, are the primary mediators, i.e., types I–III.

cell-mediated hypersensitivity  type IV h.; see Gell and Coombs classification, under classification.

contact hypersensitivity  a type IV hypersensitivity produced by contact of the skin with a chemical substance having the properties of an antigen or hapten.

cytotoxic hypersensitivity  type II h.; see Gell and Coombs classification, under classification.

delayed hypersensitivity  (DH), delayed-type hypersensitivity (DTH) that which takes 24 to 72 hours to develop and is mediated by T lymphocytes rather than by antibodies; usually used to denote the subset of type IV hypersensitivity involving cytokine release and macrophage activation, as opposed to direct cytolysis, but sometimes used more broadly, even as a synonym of type IV h.

immediate hypersensitivity 

1. type I h.; see Gell and Coombs classification, under classification.

2. occasionally, any form of hypersensitivity mediated by antibodies and developing rapidly, generally in minutes to hours (i.e., types I–III ), as distinguished from that mediated by T lymphocytes and macrophages and requiring days to develop (type IV, or delayed h. ).

immune complex–mediated hypersensitivity  type III h.; see Gell and Coombs classification, under classification.

T cell–mediated hypersensitivity  type IV h.; see Gell and Coombs classification, under classification.

type I hypersensitivity  see Gell and Coombs classification, under classification.

type II hypersensitivity  see Gell and Coombs classification, under classification.

type III hypersensitivity  see Gell and Coombs classification, under classification.

type IV hypersensitivity  see Gell and Coombs classification, under classification.

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cytotoxic hypersensitivity.

See cytotoxic anaphylaxis.

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hypersensitivity

1. a state of altered reactivity in which the body reacts with an exaggerated immune response to a foreign agent; allergy is a synonym for hypersensitivity. anaphylaxis is a form of hypersensitivity.

There are four basic types of hypersensitivity reactions: Type I (called also immediate hypersensitivity) involves cell-fixed antibody, mainly IgE attached to mast cells or basophils. Antigen binding causes the cell to release vasoactive factors. The basis for anaphylaxis and atopy. Type II causes cell destruction (cytotoxicity) by the action of immunoglobulin with complement or cytotoxic cells. Seen in red blood cell transfusion reactions and in alloimmune hemolytic anemia. See also antibody-dependent cellular cytotoxicity. Type III (called also immune-complex or subacute hypersensitivity) causes tissue damage and inflammation by the deposition of antigen-antibody complexes that activate complement and attract polymorphonuclear cells. Type IV (called also delayed hypersensitivity) involves sensitized T lymphocytes that react with cell bound or associated antigen and release lymphokines, causing mononuclear cell accumulation, tissue damage and inflammation, typically manifesting at least 24 hours after exposure to the antigen.

2. a state of increased responsivity to physical stimuli.

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hypersensitivity angiitis

variant of polyarteritis nodosa; a disease of small blood vessels in humans; called also leukocytoclastic vasculitis.

antibody-mediated hypersensitivity

types I, II and III hypersensitivity reactions. Called also immediate hypersensitivity.

bacterial hypersensitivity

immune responses to bacteria or bacterial products may contribute to the clinical features of some diseases, e.g. the anemia associated with salmonellosis, arthritis in erysipelas of pigs, intestinal lesions in Johne's disease, or be the principal cause as in staphylococcal hypersensitivity dermatitis in dogs.

contact hypersensitivity

a type IV reaction produced by contact of the skin with a low-molecular-weight chemical substance having the properties of a hapten in a sensitized individual; it includes allergic contact dermatitis.

cutaneous basophil hypersensitivity

a delayed inflammatory response characterized by large numbers of basophils.

cytotoxic hypersensitivity

type II hypersensitivity.

delayed hypersensitivity

type IV reaction. A slowly developing cell-mediated immune response in which T helper 1 lymphocytes respond to specific antigen by releasing cytokines, some of which activate macrophages, as occurs in tuberculin reaction, graft rejection, some autoimmune diseases, etc.

drug hypersensitivity

may be either an immediate (antibody mediated) or delayed type (T lymphocyte mediated) reaction. See also drug eruption.

flea bite hypersensitivity

see flea allergy dermatitis.

food hypersensitivity

hypersensitivity reaction to various dietary constituents has been the suspected cause of allergic dermatitis in most species, but conclusive evidence is often lacking. It may also result in diarrhea.

fungal hypersensitivity

may contribute to the clinical features of cutaneous fungal infections, particularly kerion formation. It is also the basis for skin testing for systemic mycoses, e.g. histoplasmin and coccidioidin.

helminth hypersensitivity

occurs, e.g. the self-cure phenomenon, and the allergic response of a sensitized animal to an invasion, e.g. of lungs, causes massive pulmonary edema.

immediate hypersensitivity

antibody-mediated hypersensitivity, i.e. types I, II and III, characterized by a response that appears within minutes to hours, resulting either from a release of histamine and other mediators of hypersensitivity from IgE-sensitized mast cells, causing increased vascular permeability, edema and smooth muscle contraction (type I), from antibody-mediated lysis of red blood cells (type II), or from immune complex mediated pathology (type III).

immune complex hypersensitivity

type III hypersensitivity (above).

mold hypersensitivity

see acute bovine pulmonary emphysema-edema.

hypersensitivity pneumonitis

see hypersensitivity pneumonitis.

staphylococcal hypersensitivity

see bacterial hypersensitivity (above).

hypersensitivity threshold

a theory that certain levels of allergens may be tolerated by some sensitized individuals without manifestations of disease, but a slight increase in the level precipitates clinical signs.

tuberculin type hypersensitivity

the classical T lymphocyte cell-mediated hypersensitivity associated with mycobacterium infection or immunization with antigens containing Freund's adjuvant.