Effects of activated T cells on natural killing.

Two populations of human blood lymphocytes--one forming rosettes with sheep erythrocytes, the other non-rosetting--are cytolytic in vitro for several long term cultured tumour-derived cell lines. A particular breast cancer-derived target cell (MDA-157) is only killed by the non-rosetting effector. Rosetting cells from normal donors infected or immunized with influenza virus augment cytolytic activity on MDA-157 targets by non-rosetting effector cells. Similar augmenting activity can be induced by incubating the rosetting population with sources of immune (gamma), but not leucocyte (alpha) interferon in vitro. This augmentation of cytolytic activity does not require compatibility at the major histocompatibility locus between the augmenting and effector populations.