Resumen

TORRES, Elza Araújo  y  RAMALHO, Renata Belmonte. O complexo HLA. Ciência educ. [online]. 1996, vol.02, pp.70-76. ISSN 1516-7313.

The human Major Histocompatibility Complex (MHC is named HLA (Human Leukocyte antigens), because its products were first defined on the surface of lymphocytes. The MHC genes are very closely located on the short arm of chromosome 6 and inherited as a codominant haplotype. MHC genes are the most polymorphic genes ever described. The extreme polymorphism of the HLA is due to the multiplicity of alleles, encoded by each of the different loci. The HLA antigens are classified as a product of the genes and can be ordered according to either their similar or different functions and expressions: class-I (HLA-A, B, C), class-I1 (HLADR, DQ, DP), class-III (C2, C4). A large number of other genes has been mapped to this region of which several are non-functional pseudogenes or genes for which no expressed protein thus have been found. The main function of the HLA complex is to collect peptides inside the cell and transport them to the cell surface to become recognized by T-cells. The interaction of T cell receptor (TCR) and the peptide presented by MHC molecule is central to self/nonself discrimination, tolerance induction and immunity. Class II molecules present peptides from endosomal compartment to helper T cells (CD4), and class I present peptides from proteins which are synthesized in the cell to cytotoxic T cells (CD8). The importance of HLA complex is in organ transplantation, paternity tests, maternal-fetal incompatibilities and disease associations.

Palabras clave : HLA; Histocompatibility; Antigens; Immunity; Genes.

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