Properties of a murine lymphokine that augments E-rosette formation.

Antigenic stimulation of spleen mononuclear cells from contact-sensitized mice produced a soluble factor that enhanced the formation of E-rosettes by human lymphocytes in vitro. Production of this murine E-rosette augmenting factor (E-RAF) occurred over a narrow range of antigen concentrations, was hapten-specific, and depended on T-lymphocytes. The factor was not dialysable, in contrast to other substances extracted from normal leucocytes. Murine E-RAF is thus a lymphokine whose action is not species restricted. It was readily detected 30 min after contact of cells with antigen. E-RAF formation by spleen cells and delayed-type hypersensitivity reactions were elicited over a similar period after contact sensitization of mice.