Enhanced NK cell activity in mice injected with interferon and interferon inducers.

Abstract

NATURAL KILLER (NK) cells constitute a distinct subgroup of cells within the immune system1,2. They are found in the lymphoid organs of several species including man and are cytolytic on contact in short-term in vitro assays for several cell types, in particular tumour cells1–5. Although the level of NK cell activity is under genetic control6,7, several extraneous agents, including bacterial adjuvants, animal viruses and NK-sensitive tumour cells induce an increase in in vivo NK cell activity6–10. Several of these agents are also known to increase the resistance of mice to transplantable tumours. This effect may be mediated by NK cells, as a positive correlation exists between in vivo resistance to syngeneic tumours and the levels of NK cell activity in the individual mice11,12. Viruses as well as several immunoadjuvants are also inducers of interferon. Here we present evidence that interferon and interferon inducers markedly enhance NK cell activity in mice, and suggest that interferon may be the mediator by which many different agents increase NK cell activity in vivo.