Activated gamma/delta T lymphocytes infiltrating renal cell carcinoma.

Gamma/delta (gamma delta) T lymphocytes have been postulated to play a role in a surveillance mechanism that eliminates transformed or otherwise damaged cells. In this study, we examined by flow cytometry the frequency and phenotype of gamma delta T cells in the tumour infiltrating lymphocytes (TIL) and peripheral blood (PBL) from renal cell carcinoma patients. The TCR gamma delta + cells comprised an average of 3.8% of the CD3+ TIL and 5.2% of circulating T cells. Analysis of surface immunophenotype revealed that activation markers of T lymphocytes: CD25 and HLA DR were highly expressed on the tumour infiltrating gamma delta + T lymphocytes (median 27.6% for CD25 and 52.0% for HLA DR). More importantly, percentage of activated gamma delta T cells was found to be much higher than compared to all activated CD3+ cells. Furthermore, an unusually high proportion of gamma delta positive TILs express CD4 or CD8 molecules (17.2 and 36.8%, respectively), indicating that they might recognise antigen presented within MHC II or I context. These results suggest that gamma delta T lymphocytes may play a certain role in immune response against tumour cells.