Analysis of the T-Cell Receptor Vα Gene Repertoire and Clonal Expansion in the Benzene-Exposed Group.

Benzene is a potent human leukemogen, but its mechanism of hematotoxicity is uncertain. It is well know that benzene inhibit T cells proliferation. Several reports revealed that clonal expansion TCR Vβ T cells could be found in workers exposed to benzene. In this study we observe the distribution of TCR Vα gene repertoire and clonal expansion in peripheral blood mononuclear cells from 9 donors and 16 workers exposed to benzene. Complementarity determining region 3 (CDR3) of TCR Vα subfamily genes were amplified using RT-PCR. The PCR products were further analyzed by genescan to evaluating clonality of T cells. 29 Vα subfamily could be detected in 9 donors.1~11 Vα subfamilies were identified in all but one of the workers studied. The most frequently expressed Vα subfamily were Vα₃, Vα₁₂ and Vα₁₉ (68.8%), Vα₁₄(56.3%), with a lower expression rate found in Vα_5,Vα₁₅, Vα₁₆, Vα ₂₂, Vα ₂₃ and Vα ₂₄ (6.3%). Clonal expansion T cells in one or more Vα subfamily were found in 12 out of all workers studied, including oligoclonal, oligocolonal trend and bioclonal patterns. The frequency of clonal expansion T cells in Vα₁₂, Vα₁₄ and Vα₁₉ subfamilies were higher than others. In conclusion, skewed distribution and clonal expansion of TCR Vα subfamily T cells could be found in workers exposed to benzene. Vα₁₂, Vα₁₄ and Vα₁₉ subfamilies may be highly sensitive to benzene exposed. This is the first report of clonal expansion TCR Vα T cells in the benzene-exposed group. The bias pattern of TCR Vα T cells may be due to the immune cytotocicity from benzene. However, whether the oligoclonality in some Vα subfamilies reflect the phenomenon of clone absense or may be a response clone to benzene-related impairment during exposed to benzene, remains an open question.