CD8+ T lymphocytes isolated from renal cancer patients recognize tumour cells through an HLA- and TCR/CD3-independent pathway

Purpose: The aim of this study was to characterize the immune response of patients affected by renal cell carcinoma (RCC). Methods: Long-term RCC lines were established by retroviral-mediated transfer of the large T-antigen of SV40 into fresh carcinoma cells. Reactive T cell effectors were generated by iterative stimulations of patients' PBMC with autologous tumour cells. Results: This protocol led to the induction of CD8⁺ T cell clones reactive against the autologous tumour, but not against NK-sensitive cell lines. However, some of these effectors recognize normal renal cells, allogeneic renal carcinoma cell lines and colon and non-small cell lung carcinomas but not melanomas and lymphoblastoid lines, without evidence of shared classical HLA class I (HLA-I) molecules. Further characterization performed on the CD8 ⁺ TCR α/β⁺ clone, CTL30, demonstrated that neither expression of CD1, HLA-Ia nor HLA-Ib, correlated with the T cells' recognition. Moreover, β2m expression by target cells was not required to achieve interaction of tumour-effector cells. In agreement with this observation, the lytic activity of CTL30 was not inhibited by anti-HLA-I Ab, and antigen expression was not affected by inhibitors of antigen processing. Lytic activity of CTL30, while partially inhibited by anti-NKG2D, could not be abolished by anti-CD3 Abs. Moreover, growth and expansion of CTL30 was sustained only by T cell interaction with antigen-expressing tumour cells; unspecific mitogenic stimuli, such as anti-CD3 and PHA, did not allow T cell expansion. These results demonstrated the existence of an α/β T cell population, recognizing epithelial tumour cells through an HLA-unrestricted, CD3-independent mechanism.