| class iv | All other intermittent streams not meeting higher class criteria. (05 Dec 1998) |
|---|---|
| class switch | Change in the isotype of antibody produced after a B-cell has encountered an antigen. (05 Mar 2000) |
| cover class | A category into which plant species would fit based upon their percent areal cover, the cover classes used (midpoints in parentheses) are T = <1% cover (0), 1 = 1-5% (3.0), 2 = 6-15% (10.5), 7 = 51-75% (63.0), 6 = 76-95% (85.5), 7 = 96-100% (98.0). (09 Oct 1997) |
| histocompatibility antigens class I | Large transmembrane, polymorphic glycoproteins noncovalently associated with nonpolymorphic beta 2-microglobulin. In humans, three structural genes on chromosome 6 code for the HLA-a, HLA-b and HLA-c antigens. In mice, three genes named k, d, and l on chromosome 17 code for the h-2 antigens. Class I antigens are found on most nucleated cells and are generally detected by their reactivity with alloantisera. These antigens are recognised during graft rejection and restrict cell-mediated lysis of virus-infected cells. They are primarily associated with rheumatologic diseases and certain malignant disorders. (12 Dec 1998) |
| histocompatibility antigens class II | Large, transmembrane, non-covalently linked glycoproteins (alpha and beta). Both chains can be polymorphic although there is more structural variation in the beta chains. The class II antigens in humans are called HLA-d antigens and are coded by a gene on chromosome 6. In mice, two genes named ia and i.e. On chromosome 17 code for the h-2 antigens. The antigens are found on B-lymphocytes, macrophages, epidermal cells, and sperm and are thought to mediate the competence of and cellular cooperation in the immune response. The term ia antigens used to refer only to the proteins encoded by the ia genes in the mouse, but is now used as a generic term for any class II histocompatibility antigen. (12 Dec 1998) |
| social class | A stratum of people with similar position and prestige; includes social stratification. Social class is measured by criteria such as education, occupation, and income. (12 Dec 1998) |
| stream class | Classification of streams based on the present and foreseeable uses made of the water, and the potential effects of on-site changes on downstream uses. Four classes are defined (05 Dec 1998) |
| immunoglobulin class switching | Gene rearrangement of the b-lymphocyte which results in a substitution in the type of heavy-chain constant region that is expressed. This allows the effector response to change while the antigen binding specificity (variable region) remains the same. The majority of class switching occurs by a DNA recombination event but it also can take place at the level of RNA processing. (12 Dec 1998) |
| first-class | Of the best class; of the highest rank; in the first division; of the best quality; first-rate; as, a first-class telescope. First-class car or First-class railway carriage, any passenger car of the highest regular class, and intended for passengers who pay the highest regular rate; distinguished from a second-class car. Source: Websters Dictionary (01 Mar 1998) |