T cell receptor Vα and Vβ gene usage by tumour-infiltrating lymphocytes in oral squamous cell carcinoma

Oral squamous cell carcinomas (SCC) are often infiltrated by a large number of T lymphocytes. To clarify the nature of the tumour-infiltrating lymphocytes (TIL), we examined T cell receptor (TCR) Vα and Vβ gene usage by TIL and peripheral blood mononuclear cells (PBMC) obtained from 10 patients with oral SCC. We obtained RNA from TIL and PBMC, synthesized complementary DNA, and used the polymerase chain reaction (PCR) method with a panel of primers specific for the V gene segment subfamily (Vα1-18/Vβ1-20). We thus found that TIL showed more restricted usage of Vβ gene families in contrast to PBMC of the same patients while two unique Vβ gene (Vβ6 and Vβ5.2) segment transcripts were overexpressed in the TIL of more than half of the patients. On the other hand, no major difference was observed in the Vα gene usage between the TIL and PBMC of most patients. To characterize these T cell subpopulations with unique Vβ gene segment transcripts further, we sequenced the complementarity-determining region 3 in Vβ6-Cβ and Vβ5.2-Cβ PCR products derived from TIL and PBMC of two selected patients in each case. Although no usage of the conserved amino acid sequence by TIL was detected, the frequent use of Vβ6/Jβ1.1 in one patient and the Vβ6/Jβ2.7 gene segments in another patient was observed. Regarding the Vβ5.2 transcripts, obtained from the other two patients, no preferential usage of specific Jβ gene segments by TIL was observed. These results suggest that the unique T cell populations are amplified in patients with oral SCC, possibly as a consequence of an in situ immune reaction.