| IntroductionAs one of the important marker of human cell surface, HLA( Human leukocyte antigen) is the most complicated human dominant polymorphic genetic system because of its high homogeneity and complicated polymorphism. It differs significantly in different regions and races, which can be regarded as the best sign of colony genetic character and used for investigating disease susceptibility group distribution and disease association study. The HLA system is the most polymorphic of all human genetic systems. It plays an important role in aspects of antigen recognition, presentation, immune response and regulation. HLA genes locate in human chromosome 6p21.3 region. HLA class I gene spans approximately 1500 kb, encoding transplanting antigen. This region consists of a large number of immunologically relevant genes, including loci HLA-A, B, C, D, E, F, G, H, I, J, L and K. HLA-A, B, C genes have similar configuration , spanning approximately 4000 ~ 5000 bps. The class I gene consists of genes encoding a chain and (32m chain. Gene encoding a chain has 8 exons, in which has polymorphic exon 2 and exon 3 and conservative exon 4. Exon 2, 3 and 4 encode functional region a1, a2, a3 in heavy chain of HLA class I molecules. 30% amino acid sequences vary in al and o2 region because of the polymorphism of alleles. The class I antigen is the proteinic product encoded by different RNA, which has different antigenic determinants. Therefore, the polymorphism of HLA-A, B, C originate from region al and a2. HLA class II gene spans approximately 1000 kb, which consists of a lot of immunologically relevant genes, too. These gene include HLA-DR, HLA-DQ and HLA-DP, which has similar configuration. DR region consists of 1 a gene,4B genes in which 2B genes are pseudogenes. B gene is polymorphic, while a gene is conservative.The polymorphism of class II molecules presents in region B1. HLA-DR antigen is the most important antigen of immune response in heterogenous transplantation. It is more important than class I molecules. The speciality of HLA-DR comes from the highly polymorphic DRB1 locus alleles. DNA typing for HLA locus is necessary for donor selection of organ transplantation, individual identification in forensic medicine, disease and HLA association study and anthropological research.Serological research of HLA began in early 1960's. Microlymphocytotoxic-ity assay of HLA typing was the basic method and technique for immune genetic study and MHC (Major histocompatibility complex) research, which was established by Terasaki in 1964 and certificated as international standard technique by NIH (National Institutes of Health) in 1970. In late 1980' s, HLA methodology developed from serology to modern molecular biology and from detecting in cellular level to detecting in molecular level with the development of technology and interaction of new subject knowledge. The establishment of PCR technique provided an effective method and shortcut for application of molecular biology in HLA research field. After the 11th International Histocompatibility Workshop and Conference held in 1991, HLA research went into DNA typing stage from serological study stage.Sequence specific oligonucleotide probes (SSOP) method was first used for detecting HLA class II genes by Saiki and his fellows in 1986. This method has the advantages of a greater accuracy and speciality, a higher level of resolution and fewer sample demanded compared with serological typing. But for HLA class I genes, it was difficult to use this method, especially for large clinical samples, because class I gene was more complicated, demanding bigger SSOP sets and there were a lot of sharing sequences between alleles in class I HLA genes.Because the genetic differentia among individuals originated from the genes encoding antigen protein, DNA typing was undoubtedly the most accurate method. It had greater accuracy than serological typing and cytological typing, and replaced the latter gradually. The most accurate sequencing typing method was first used for HLA-DRB1,...
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