Histamine-releasing activity of mouse spleen cell culture supernatants.

Histamine releasing factor (HRF) generated in vitro by spleen cells of immunized mice activates homologous peritoneal mast cells (both normal and sensitized) for small but consistent, dose-dependent histamine and 5-hydroxytryptamine release. Both the time-course of this release and its susceptibility to the enhancing effect of D2O were similar to those observed in IgE-induced release; however, simultaneous challenge of sensitized mast cells with HRF and specific antigen or anti-IgE showed an additive effect, suggesting that mediator release by HRF and by the IgE system are independent of one another.