| Webster's Online Dictionary |
| Expressions | Domain | Definition | |
| Histocompatibility antigens | Geology | The antigens on cells which are responsible for rejection of foreign body tissue such as grafts transplanted from a genetically dissimilar donor. (references) | |
| Histocompatibility Antigens | Health | A group of antigens that includes both the major and minor histocompatibility antigens. The former are genetically determined by the major histocompatibility complex. They determine tissue type for transplantation and cause allograft rejections. The latter are systems of allelic alloantigens that can cause weak transplant rejection. (references) | |
| Histocompatibility Antigens Class I | Health | 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 recognized during graft rejection and restrict cell-mediated lysis of virus-infected cells. They are primarily associated with rheumatologic diseases and certain malignant disorders. (references) | |
| Histocompatibility Antigens Class II | Health | 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 IE 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. (references) | |
| Minor Histocompatibility Antigens | Health | Allelic alloantigens often responsible for weak graft rejection in cases when (major) histocompatibility has been established by standard tests. In the mouse they are coded by more than 500 genes at up to 30 minor histocompatibility loci. The most well-known minor histocompatibility antigen in mammals is the H-Y antigen. (references) | |
| Minor histocompatibility antigens | Religion | These antigens, encoded outside the MHC, are numerous, but do not generate rapid graft rejection or primary responses of T cells in vitro. They do not serve as restricting elements in cell interactions. (references) | |
Source: compiled by the editor from various references; see credits. | Top | ||
