The emergence of non-cytolytic NK1.1+ T cells in the long-term culture of murine tumour-infiltrating lymphocytes: A possible role of transforming growth factor-β

Abstract

The mechanism by which murine tumour-infiltrating lymphocytes (TIL) decreased their anti-tumour activity during an in vitro culture with interleukin-2 (IL-2) was investigated. A phenotypic analysis revealed that the TIL cultured for 7 days (TIL-d7) were exclusively NK1.1- CD4- CD8+ CD3+ cells and that this population was replaced by natural killer (NK) 1.1+ CD4- CD8- CD3+ cells by day 27 (TIL-d27) during the culture of TIL. The TIL-d7 cells showed a cytolytic activity against B16 melanoma, whereas the TIL-d27 cells had lost this activity, suggesting that the decrease in the antitumour effect of TIL during the culture with IL-2 was due to their populational change. Analysis on the characteristics of the TIL-d27 cells revealed that they expressed skewed T-cell receptor (TCR) Vβ5 and increased mRNA expression of Vα 14. In addition, they expressed transforming growth factor-β (TGF-β) mRNA. Interestingly, TGF-β augmented the proliferation of TIL-d27 cells under the presence of IL-2, but suppressed that of TIL-d7 cells. Moreover, the proliferation of TIL-d27 cells was suppressed by anti-TGF-β monoclonal antibody. Collectively, these results suggest that, in contrast to its suppressive effect on anti-tumour effect vor T cells, TGF-β could be an autocrine growth factor for NK1.1+ T cells and thereby induce non-cytolytic NK1.1+ T cells in the long-term culture of TIL.