The tumor disappearance reaction: an in vivo effect of a noncytotoxic lymphokine active against tumor cells.

A lymphokine, tumor migration inhibition factor (TMIF), that can inhibit the migration of tumor cells in vitro without cytotoxic effect has been described. TMIF can be produced in vitro or in vivo. In the present study, it is demonstrated that administration of TMIF can lead to a transient decrease in recoverable tumor cells from the peritoneal cavities of otherwise untreated mice. This result, which appears to be due to a direct effect of the mediator, rather than a consequence of inflammatory cell accumulation, is analogous to the effect of macrophage migration inhibition factor (MIF) on macrophages in the well known macrophage disappearance reaction. These findings demonstrate that TMIF can exert an effect in vivo predicted from its in vitro properties, and raise the possibility that this effect can be exploited in an appropriate therapeutic model.