univalent antibody

u·ni·va·lent an·ti·bod·y

an "incomplete" form of antibody that has a single binding site; in the case of Rh+ erythrocytes, such an anti-Rh antibody may coat the cells but not cause them to agglutinate in saline; however, agglutination does occur when such coated cells are suspended in serum or other protein media, such as albumin, therefore called serum agglutinin.

Synonym(s): incomplete antibody (1) , inhibiting antibody

u·ni·va·lent an·ti·body

(yū'ni-vā'lĕnt an'ti-bod-ē)

An "incomplete" form of antibody that may coat antigen, but which according to the "lattice theory" does not have a second receptor for attachment to another molecule of antigen; in the case of Rh+ erythrocytes, such an anti-Rh antibody may coat the cells but not cause them to agglutinate in saline; however, agglutination does occur when such coated cells are suspended in serum or other protein media, such as albumin, therefore called serum agglutinin.
Synonym(s): incomplete antibody (1) .

antibody

specialized serum proteins produced by B lymphocytes in response to an immense number of different antigens (>10⁷) to which an animal may be exposed. Antibody produced by a particular antigen combines with that antigen only. The exquisite specificity of Ab for the antigen that stimulated its production is the basis for all antibody-antigen reactions both in vivo and in vitro. Antibodies are heterodimers composed of two light (L) and two heavy (H) chain polypeptide molecules. The amino termini of the L and H chains have a variable amino acid sequence V_L and V_H. The specificity of Ab for Ag is conferred by the V_L and V_H domains. There are five major classes of antibody, designated IgG, IgM, IgA, IgD and IgE. Abbreviated Ab or Ig. Called also immunoglubulin or gamma globulin. See also immunity.

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affinity purification of antibody

see immunofiltration.

anaphylactic antibody

antibody, usually IgE, formed after the first injection of certain allergens and responsible for the signs of anaphylaxis following subsequent exposures to the same allergen.

antibody-antigen reaction

the specific combination of antigen with homologous antibody resulting in the reversible formation of antibody-antigen complexes that differ in composition according to the antibody-antigen ratio. See also antigen.

antinuclear antibody (ANA)

autoantibodies directed against components of the cell nucleus, e.g. DNA, RNA and histones; they may be detected by immunofluorescence. A positive ANA test is characteristic of systemic lupus erythematosus, Sjögren's syndrome and rheumatoid arthritis.

anti-idiotype antibody

antibodies against the antibody variable region.

anti-immunoglobulin antibody

those produced against an immunoglobulin, often used as reagents to study immunoglobulin molecules.

antiplatelet antibody

see antiplatelet antibody.

antispermatozoal antibody

produced following entry of sperm into the bloodstream, e.g. following rupture of the epididymis as in Brucella ovis infections.

blocking antibody

circulating antibody (usually IgG) that reacts preferentially with an antigen, preventing it from reacting with a cell-bound antibody (IgE) and blocking the induction of anaphylaxis.

antibody classes

see immunoglobulin.

clonotypic antibody

clone specific antibody.

cold-reacting antibody

see cold agglutinin.

complement-fixing antibody

immunoglobulins of the IgG or IgM class which bind complement.

cross-reacting antibody

one that combines with an antigen other than, but structurally related to, the one that induced its production.

cytophilic antibody

cytotropic antibody (below).

cytotoxic antibody

that which binds antigens expressed on the cell surface, which may (a) activate the complement pathway or (b) activate killer cells, resulting in cell lysis.

cytotropic antibody

those that attach to tissue cells (such as IgE to mast cells and basophils) that have an Fc receptor.

antibody-dependent cell-mediated cytotoxicity (ADCC)

a cytotoxic reaction in which nonsensitized cells bearing Fc receptors recognize target cells that have antibody bound to antigen exposed in the cell membrane of the target cell.

fluorescent antibody

see fluorescence microscopy.

heteroclitic antibody

one with greater affinity for an antigen other than the one that stimulated its formation.

hormonal antibody

has been investigated mostly as a means of controlling fertility in animals. See also contraception.

humoral antibody

see humoral immunity.

immune antibody

one induced by immunization or by transfusion incompatibility, in contrast to natural antibodies.

incomplete antibody

an antibody which combines with antigen without producing an observable reaction such as agglutination; originally used to describe Rh antibodies.

maternal a's

those passively transferred from dam to fetus or neonate, transplacentally or via colostrum or yolk sac. See also passive immunity.

antibody-mediated cytotoxicity

damage to cells, especially erythrocytes, caused by the reaction of antibodies (IgG, IgM or IgA) with cell surface antigens.

antibody-mediated immunity

humoral immunity.

monoclonal antibody

see monoclonal antibodies.

natural a's

ones that react with antigens to which the individual has had no known exposure. The best examples are anti a and b antibodies present in serum of humans of blood group B and A, respectively.

neutralizing antibody

one that reduces, destroys or blocks infectivity of an infectious agent, particularly virus, by partial or complete destruction of the agent.

nonagglutinating antibody

see incomplete antibody (above).

polyclonal antibody

a collection of immunoglobulins that react against the same or different antigenic determinants of the one antigen molecule.

protective antibody

one responsible for immunity to an infectious agent.

reaginic antibody

see reagin and immunoglobulin E.

antibody repertoire

all the antibody specificities that can be produced by an individual.

saline antibody

complete antibody.

skin-sensitizing antibody

see reagin.

univalent antibody

see incomplete antibody (above).