Characterisation of γδ T cells in renal cell carcinoma patients by polymerase chain reaction analysis of T cell receptor transcripts

Abstract

 Renal cell carcinomas (RCC) contain tumour infiltrating lymphocytes (TIL) but these are essentially immunosuppressed in that they do not generate effective antitumour immune responses in vivo. These TIL comprise predominantly αβ T cells, although γδ T cells are also present. The repertoire of γδ T cells in RCC, however, has not been fully investigated. To identify the γδ T cell populations infiltrating RCC, this study has characterised the γδ T cell receptor (TCR) repertoire expression in these tumours and compared this to autologous normal kidney and autologous peripheral blood. A semi-quantitative reverse transcriptase/polymerase chain reaction technique was used for amplification of rearranged TCR V-C mRNA transcripts. Primers specific for the four human TCR Vγ and six Vδ subfamilies were used, each in conjunction with a primer specific for either the Cγ or Cδ region. The specificity of the PCR products was confirmed by Southern blotting and hybridisation with an internal C region probe. A densitometry score was assigned to each DNA band and the level of V gene expression was determined as a ratio of Cδ gene expression. The γδ TCR expression in each sample was determined as a ratio of Cδ: glyceraldehyde phosphate dehydrogenase densitometry score. This demonstrated that TCR Cδ gene expression was significantly higher in RCC compared to normal kidney (P<0.019), suggesting a selective infiltration of γδ T cells into the tumour. Furthermore, we observed differences in the TCR Vγ and Vδ repertoires between RCC and peripheral blood. Vγ1 expression was significantly decreased (P<0.043) whereas there was an over-representation of Vγ4 transcripts (P<0.028) in RCC compared to blood. A significant reduction in expression of both Vδ1 (P<0.028) and Vδ3 (P<0.051) was also observed within kidney tumour compared to peripheral blood. These findings show that expression of the γδ TCR repertoire in RCC differs from that in peripheral blood and normal kidney.