Regulation of lymphokine-activated killer activity and pore-forming protein gene expression in human peripheral blood CD8+ T lymphocytes. Inhibition by transforming growth factor-beta

Abstract

The effect of transforming growth factor-beta 1 (TGF-beta) on activation-induced CD8+ T cell cytotoxicity and gene expression was investigated. TGF-beta was demonstrated to inhibit pore-forming protein (PFP) mRNA expression and total benzoyloxycarbonyl-L-lysine thiobenzyl ester esterase activity in CD8+ T cells cultured with IL-2 and OKT3 mAb for 6 to 18 days. Consistently, in the absence or presence of TGF-beta, the PFP mRNA expression and lymphokine-activated killer (LAK) activity of CD8+ T cells were closely correlated. The inhibitory effects of TGF-beta on both CD8+ T cell PFP mRNA expression and LAK activity were reversible by removal of TGF-beta from the culture. Expression of lymphokines, adhesion/recognition molecules, and activated p55 IL-2R, previously implicated in the lytic mechanism of cytotoxic lymphocytes, either was not detectable or did not correlate with TGF-beta inhibition of LAK activity. In addition, independently of effector/target cell binding, the lectin- or heteroconjugated antibody-dependent cellular cytotoxicity of IL-2/OKT3 mAb-activated CD8+ T cells was inhibited by preculture with TGF-beta. TGF-beta also inhibited the rapid activation-induced expression of PFP mRNA and cytotoxic potential in resting T cells, thereby indicating that the effect of TGF-beta was independent of T cell proliferation. TGF-beta inhibition of CD8+ T cell PFP mRNA expression and cytotoxic potential was TGF-beta dose dependent; however, a variety of activation stimuli (including IL-2, IL-6, and OKT3 mAb) were all similarly inhibited by TGF-beta. Therefore, TGF-beta may be an important general regulator of CD8+ T cell cytotoxic function, in particular by suppressing expression of PFP, a major cytolytic protein implicated in the lytic function of cytotoxic lymphocytes.