antibody diversity (medicine) and Lung (medicine)

antibody diversity (medicine)

antibody diversity

The phenomenon of immense variability characteristic of antibodies, which enables the immune system to react specifically against the essentially unlimited kinds of antigens it encounters. Antibody diversity is accounted for by three main theories: 1) the germ line theory, which holds that each antibody-producing cell has genes coding for all possible antibody specificities, but expresses only the one stimulated by antigen; 2) the somatic mutation theory, which holds that antibody-producing cells contain only a few genes, which produce antibody diversity by mutation; and 3) the gene rearrangement theory, which holds that antibody diversity is generated by the rearrangement of variable region gene segments during the differentiation of the antibody-producing cells.

Lung (medicine)

lung
<anatomy> An organ for aerial respiration; commonly in the plural. "My lungs began to crow like chanticleer." (Shak)

In all air-breathing vertebrates the lungs are developed from the ventral wall of the oesophagus as a pouch which divides into two sacs. In amphibians and many reptiles the lungs retain very nearly this primitive saclike character, but in the higher forms the connection with the oesophagus becomes elongated into the windpipe and the inner walls of the sacs become more and more divided, until, in the mammals, the air spaces become minutely divided into tubes ending in small air cells, in the walls of which the blood circulates in a fine network of capillaries. In mammals the lungs are more or less divided into lobes, and each lung occupies a separate cavity in the thorax. See Respiration.

<medicine> Lung fever, pneumonia.

<botany> Lung flower, one of the breathing organs of spiders and snails.

Origin: OE. Lunge, AS. Lunge, pl. Lungen; akin to D. Long, G. Lunge, Icel. & Sw. Lunga, Dan. Lunge, all prob. From the root of E. Light. See Light not heavy.

Source: Websters Dictionary

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