Further biochemical characterization of human basophil-like cell-promoting activity and its distinction from human interleukin-3-like activity.

Supernatants from lectin-stimulated human peripheral blood mononuclear cells contained two activities; basophil-like cell-promoting activity (BaPA) and a growth factor for murine interleukin-3-dependent cell lines (IL-3-like activity). BaPA had a MW of 24,000 and a pI of 6.0-7.5, while human IL-3-like activity had a MW of 18,000 and a pI of 5.0-5.9. Beside the biochemical differences between the two activities, supernatants from a T cell line were found that contained BaPA and GM-CSF but no IL-3-like activity. These data suggest that BaPA and IL-3-like activity are two different molecular entities.