T-cell growth factor contains activity that supports natural killer activity in vitro.

Lymphocytes from athymic and normal mice were tested and compared for cytotoxic activity after in vitro cultures supplemented with concanavalin A or T-cell growth factor (TCGF). Our results indicate that, in addition to cytotoxic T cells, natural killer (NK) activity can be recovered from lymphocytes cultured in the presence of TCGF and that this is not the result of contaminating interferon in the TCGF preparations. The NK nature of the effector cells was established by means of a panel of target cells, including a teratocarcinoma tumour cell, which enabled the distinction of T-cell- and NK-cell-mediated lysis.