Human leukocyte antigen immune response

Contamination of blood products with lymphocytes can lead to transfusion-induced reactions ranging from a mild fever to severe reactions such as alloimmunization and graft versus host disease (GvHD), in which the transfused lymphocytes (graft) survive the defensive immune reaction of the patient (host) and start a reaction which destroys the cells of the host. The patient also may develop an immune response to the human leukocyte antigen (HLA) type of the graft s cells and reject all platelet transfusions that do not match their own HLA system. The HLA system, found on blood platelets and lymphocytes, is more compHcated than, but similar to, the ABO blood group system of red cells. 

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). 

For type 1 DM, the concordance rate for identical twins is only 25—50% and environmental influences must have an important role. Type 1 DM involves an autoimmune attack on the pancreatic /3 cells. Antibodies to islet cell antigens are detected in up to 80% of patients with type 1 DM shortly after diagnosis or even prior to the onset of clinical disease. Type 1 DM is associated with specific human leukocyte antigen (HLA) alleles, especially at the B and DR loci, and the HLA complex is known to play critical roles in the immune response. However, the trigger for the immune response remains unknown. In about 10% of new cases of type 1 DM, there is no evidence of autoimmune insulitis. The ADA and the World Health Organization (WHO) therefore subdivide this disease into autoimmune (lA) and idiopathic (IB) subtypes. 

The combination of microarrays and the studious apphcation of programs to scan these resulting databases provide insight into complex phenomena like Human Leukocyte Antigen group DR (HLA-DR) in the immune response. 

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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