The major histocompatibility complex (MHC) is a set of cell surface molecules encoded by a large gene family in all vertebrates. MHC molecules mediate interactions of leukocytes, also called white blood cells (WBCs), which are immune cells, with other leukocytes or body cells. MHC determines compatibility of donors for organ transplant as well as one's susceptibility to an autoimmune disease via crossreacting immunization. In humans, MHC is also called human leukocyte antigen (HLA). Protein molecules—either of the host's own phenotype or of other biologic entities—are continually synthesized and degraded in a cell. Occurring on the cell surface, each MHC molecule displays a molecular fraction, called epitope, of a protein.[1] The presented antigen can be either self or nonself. On the cell membrane, the MHC population in its entirety is like a meter indicating the balance of proteins within the cell.
The MHC gene family is divided into three subgroups: class I, class II and class III. Diversity of antigen presentation, mediated by MHC classes I and II, is attained in at least three ways: (1) an organism's MHC repertoire is polygenic (via multiple, interacting genes); (2) MHC expression is codominant (from both sets of inherited alleles); (3) MHC gene variants are highly polymorphic (diversely varying from organism to organism within a species)
Of the three MHC classes identified, human attention commonly goes to classes I and II. MHC class II mediates immunization to an antigen—that is, specific immunity, aka acquired immunity or adaptive immunity—and MHC class I thereafter mediates destruction of host cells displaying that antigen. Thus cellular immunity occurs. (The other arm of specific immunity is humoral immunity, whose relation to MHC is more indirect.)
------------------------------
إن كان لديك معلومات آخرى يمكنك إضافتها لتعم الفائدة على الجميع , إعمل share "مشاركة" لطفاً إن عجبتك المعلومة
----------------------------
The MHC gene family is divided into three subgroups: class I, class II and class III. Diversity of antigen presentation, mediated by MHC classes I and II, is attained in at least three ways: (1) an organism's MHC repertoire is polygenic (via multiple, interacting genes); (2) MHC expression is codominant (from both sets of inherited alleles); (3) MHC gene variants are highly polymorphic (diversely varying from organism to organism within a species)
Of the three MHC classes identified, human attention commonly goes to classes I and II. MHC class II mediates immunization to an antigen—that is, specific immunity, aka acquired immunity or adaptive immunity—and MHC class I thereafter mediates destruction of host cells displaying that antigen. Thus cellular immunity occurs. (The other arm of specific immunity is humoral immunity, whose relation to MHC is more indirect.)
------------------------------
إن كان لديك معلومات آخرى يمكنك إضافتها لتعم الفائدة على الجميع , إعمل share "مشاركة" لطفاً إن عجبتك المعلومة
----------------------------
ليست هناك تعليقات:
إرسال تعليق