Functional role of IL-2 receptors on tumour-infiltrating lymphocytes

This study was undertaken to investigate the pathways involved in the interleukin 2 (IL-2)-driven growth of tumour-infiltrating lymphocytes (TILs). For this purpose, TIL lines and freshly isolated TILs obtained from 16 patients with solid cancer (three melanoma, seven primary colorectal carcinoma, four hepatic metastases from colorectal cancer and two lung cancer) were evaluated for (a) expression of IL-2 receptor (IL-2R) both at the RNA level and on the cell surface by flow cytometric analysis and (b) their proliferative activity in response to IL-2 and the role of IL-2R subunits in the IL-2-driven TIL growth. Northern blot analysis showed that TILs express a strong message for both the p55 and the p75 IL-2R. Accordingly, flow cytometric analysis demonstrated that TILs bear both IL-2R chains. TILs cultured in vitro in the presence of rIL-2 were able to proliferate in response to different concentrations of this cytokine. Monoclonal antibodies (MAbs) specifically recognising the p55 and p75 IL-2R chains (anti-Tac and TU27 respectively) exhibited a marked inhibitory effect on IL-2-driven growth when added individually or in appropriate combinations. Our results demonstrated that TILs are equipped with a fully functional IL-2 receptor system, thus suggesting the involvement of this structure in the activation and expansion of TILs following immunotherapy with IL-2.