Immune response human leukocyte antigen molecules

Human leukocyte antigens are polymorphic cell-surface molecules that are intimately involved in the regulation of the immune response. The antigens are encoded by a series of closely linked genes known as the major histocompatibility complex (MHC), which is located on the short arm of chromosome 6 (BIO). The complex extends over approximately 4000 kilobases or 4 x 10 nucleotides and contains three distinct subregions known as class I, class II, and class III (T19) (see Fig. 1). 

Tissue type is determined hy molecules on the surface of every cell in the body. These molecules are called human leukocyte antigens (HLA) or the major histocompatibility complex (Petersdorfet et al. 1998 Villard 2006). Each person has unique HLAs. The HL As on the cells of the transplant signal to the body that this tissue is foreign, when a person receives a transplant, and stimulate an immune response. The recipient s blood usually is screened for antibodies against the tissues of the specific potential donor. If these antibodies are present severe rejection is expected, and transplantation will not be performed in these cases (Matas and Schnitzler 2004 Talbot and Manas 1997). 

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