POLYMORPHISM DETECTION AND SEQUENCE-ANALYSIS OF HUMAN T-CELL RECEPTORV-ALPHA-CHAIN-ENCODING GENE SEGMENTS

The T-cell receptor (Tcr) provides specificity for antigen recognition by its variable domain, primarily consisting of two germline encoded variable (V) region gene segments. Thus it has been suggested that inh erited polymorphisms in the TCRV gene segments could contribute to dif ferential immune responsiveness (e. g., autoimmunity) in human populat ions. In the present study, we have sought potentially functional poly morphisms in the germline TCRAV gene segments. Using denaturing gradie nt gel electrophoresis on polymerase chain reaction (PCR)-amplified pr oducts from the pooled DNA of many individuals, we identified polymorp hisms in the TCRAV2S1, AV4S1, AV7S1, and AV8S1 gene segments. A comple te DNA sequence analysis of these PCR products identified polymorphism s that affected amino acids in the predicted antigen-binding regions o f the Tcr alpha chain, as well as polymorphisms in the introns. Genoty pe analysis of all nine DNA point mutations showed a 5%-50% range (ave raging 35%) of minor allele frequencies, often resulting in individual s homozygous for the alternate allele forms. All possible haplotype co mbinations of the amino acid-affecting polymorphisms were found, indic ating that in human populations there are a large number of different germline haplotypes encoding V gene segment alleles. These TCRAV codin g region polymorphisms provide the rationale for, and allow the direct testing of, hypotheses concerning inherited polymorphisms within the T-cell receptor genes that may contribute to autoimmune susceptibility .