TGF beta down-regulates TLiSA1 expression and inhibits the differentiation of precursor lymphocytes into CTL and LAK cells.

This study analysed the regulatory effects of transforming growth factor beta (TGF beta) on the expression of a 70,000 MW cell surface activation antigen, TLiSA1, involved in the differentiation of cytotoxic T lymphocytes (CTL) and lymphokine-activated killer (LAK) cells from their precursor(s), and also examined the role of TGF beta in the generation of these functional cells. TGF beta was shown to suppress the expression of TLiSA1 and to inhibit, in a dose-dependent manner, the generation of both CTL and LAK cells when present from the beginning of mixed lymphocyte culture; the same inhibitory effect upon the development of cytotoxic effector cells was observed with a monoclonal antibody and with monospecific rabbit antibodies against the TLiSA1 protein. Antibody to TGF beta reversed the inhibitory effect of the cytokine on differentiation and on TLiSA1 expression. Exogenous IL-2 or, to a lesser extent, tumour necrosis factor alpha (TNF alpha) added to mixed lymphocyte cultures (MLC) augmented both TLiSA1 antigen expression and cytotoxic function by the resulting blast cells; the co-addition of TGF beta inhibited both of these cytokine-mediated effects. Similarly, it was shown that phytohaemagglutini (PHA)-induced lymphoblasts up-regulate their surface expression of TLiSA1 and exhibit increased LAK activity in response to IL-2, and TGF beta inhibited both of these events; this IL-2-induced increase in LAK cell function was also inhibited by antibodies to TLiSA1. It is suggested that TLiSA1 antigen expression is intimately linked to the differentiation of cytotoxic effector cells and that such differentiation may be a distinct process from IL-2-induced proliferation, although both events can be regulated by TGF-beta.