GENETIC INFLUENCE ON THE SHAPING OF THE HUMAN T-CELL RECEPTOR REPERTOIRE - QUANTITATIVE ASSESSMENT BY COMPETITIVE POLYMERASE CHAIN-REACTION

It has been difficult to define the different factors which contribute to the shaping of the human T-cell receptor (TCR) repertoire. In this study, the influence of the polymorphic human leucocyte antigen (HLA) genes and non-HLA genes on the phenotype of the TCRBV segment reperto ire was assessed in a population of HLA class I-matched individuals in cluding three pairs of siblings. The gene expression levels of 24 TCRB V families were evaluated in the CD4(+) and CD8(+) T-cell subsets of u nstimulated peripheral blood mononuclear cells (PBMC) by reverse trans cription (RT) and a newly developed competitive polymerase chain react ion (cPCR) assay. Titration experiments demonstrated that the RT-cPCR assay was suitable for an accurate quantification of the relative TCRB V segment expression levels. The T-cell repertoires of HLA-identical s iblings were found to be more similar than the repertoires of unrelate d individuals. On the other hand, there was no difference in the degre e of similarity between the TCRBV repertoires of CD4(+) T-cells of HLA class II identical or non-identical unrelated individuals. Furthermor e, although most of these individuals had identical HLA class I genes and non-identical HLA class II genes, the TCRBV repertoires of the CD4 (+) T cells exhibited significantly lower variabilities than the reper toires of the CD8(+) T cells. The results of the RT-cPCR assay were su pported by flow cytometric analysis of the CD4(+) and CD8(+) T-cell su bsets of the same eight individuals employing 10 different TCRBV segme nt-specific monoclonal antibodies. These observations argue for a pred ominant role of non-HLA or non-polymorphic HLA determinants for the sh aping of the TCRBV repertoire.