SEQUENCE VARIABILITY OF THE DQB1 AND DQB2 UPSTREAM REGULATORY REGION IN CHIMPANZEES (PAN TROGLODYTES) AND HUMANS.
          S Reichstetter, R Bontrop, R Wassmuth.   Institute for Clinicical Immunology, University of Erlangen-Nürnberg, Erlangen, Germany; Biomedical Primate Research Center, Dept. of Immunobiology, Rijswijk, Netherlands.
          Pronounced polymorphism is a hallmark of MHC genes.  Interestingly, polymorphism also extends into the upstream regulatory region (URR), where isotypic and allelic differences have been detected.  In this study the DQB URR polymorphism in the chimpanzee (Pan troglodytes) has been evaluated and compared to the human DQB1 and DQB2 URR, termed QBP1 and QBP2, respectively.  For the analysis of the chimpanzee QBP2, direct sequencing of the PCR product containing the region between -620 bp to +1 bp (ATG start codon) was carried out.  The same primers and PCR conditions which had been employed in humans previously were used.  QBP1 sequences were obtained after cloning of PCR product.  In chimpanzee, sequence information was obtained in 14 individuals for a homologous 620 bp QBP1 stretch and for a 260 bp QBP2 fragment.  At least 8 different QBP1 sequences were found in chimpanzees with 81 polymorphic positions (13.1 %) whereas QBP2 contained 3 different alleles with 2 polymorphic positions.  Thus, the degree of interallelic similarity for QBP1 in chimpanzees was essentially the same as in humans, where 10 QBP1 with 89 polymorphic positions and 2 QBP2 alleles with a single T to C exchange are known. When both species were compared, 89 differences for the QBP1 consensus sequences were detected.  Of these 89 differences, only three positions were species-specific and non-polymorphic.  The chimpanzee QBP2 sequences exhibited the same set of deletions and point mutations characteristic for the human QBP2 alleles. In a total of three QBP2 differences, two polymorphic differences and one non-polymorphic difference between humans and chimpanzees was detected. In conclusion, chimpanzee QBP1 and QBP2 variants closely resemble their human counterparts, suggesting that also DQB1 is expressed in chimpanzee while DQB2 is a pseudogene.