[Induction of thymocyte proliferation with B cell stimulatory factor-1].

Murine B cell stimulatory factor (BSF)-1 or interleukin 4 has been shown to regulate various aspects of B cell activation and differentiation. More recently it has been shown that this lymphokine is also involved in the regulation of T cell and mast cell proliferation. In this study we purified BSF-1 activity from supernatants of T cell hybridoma FS6-14. 13 and tested its activity on a variety of in vitro assays. It was found that the purified BSF-1 material has various activities previously ascribed to BSF-1, and interestingly enough it also induces strong proliferation of thymocytes in collaboration with phytohemagglutinin. These results strongly suggest that BSF-1 plays a regulatory role in thymocyte differentiation and further support the notion that lymphokines generally have a broad spectrum of activity.