title: Molecular studies of a rare DR2/LD-5a/DQw3 HLA class II haplotype. Multiple genetic mechanisms in the generation of polymorphic HLA class II genes.
abstract: A cDNA library was constructed from a homozygous B lymphoblastoid cell line (REM) obtained from an individual of a long isolated American Indian tribe, the Warao. The REM cell line expresses serologically defined determinants, DR2 and DQw3, and the T lymphocyte-defined (Dw/LD) specificity, LD-5a. T cells can recognize differences between FJO (a DR2/DQw1 cell line that expresses the Dw specificity MN2) and REM for both DR and DQ molecules. cNDA clones encoding the polymorphic DR beta 1-, DR beta 2-, DQ beta-, and DQ alpha-chains were sequenced and compared with other DR and DQ gene sequences. The DR beta 1-sequence of REM is identical to the DR beta 1-sequence of FJO; the DR beta 2-sequence is also identical to that of FJO except for one amino acid difference at position 67 in the polymorphic first domain (Leu in REM, Phe in FJO) due to a single point mutation. The DQ beta-sequence is identical to that of DR4/DQw3 haplotype; the DQ alpha is different from the DQ alpha of DR4/DQw3 haplotype and identical to the DQ alpha of both the DR3/DQw2 haplotype of a Raji cell line and the DR5/DQw3 haplotype in deduced amino acid sequence. Taken together, these findings suggest that: 1) a single amino acid difference (position 67) in the third hypervariable region of the first domain of the DR beta 2-chain in the DR2 haplotype is apparently sufficient for stimulating T cell responses; 2) the DQw3 serologic specificity may be defined mainly by the DQ beta-rather than DQ alpha-chain; and 3) multiple genetic events have probably occurred to generate the rarely found REM (DR2/LD-5a/DQw3) haplotype.
mesh_terms: D000595:Amino Acid Sequence; D001402:B-Lymphocytes / Q000032:analysis; D001483:Base Sequence; D002460:Cell Line; D003001:Cloning, Molecular; D004247:DNA / Q000302:isolation & purification; D005802:Genes, MHC Class II; D006681:HLA-D Antigens / Q000235:genetics*; D006683:HLA-DQ Antigens / Q000235:genetics*; D006684:HLA-DR Antigens / Q000235:genetics*; D006239:Haplotypes; D006801:Humans; D008957:Models, Genetic; D008969:Molecular Sequence Data; D011110:Polymorphism, Genetic
chemical_list: D006681:HLA-D Antigens; D006683:HLA-DQ Antigens; D006684:HLA-DR Antigens; D004247:DNA