INVOLVEMENT OF P59FYN(T) IN INTERLEUKIN-5 RECEPTOR SIGNALING

Previous studies implicate the nonreceptor protein tyrosine kinase (PT K) p59(fyn) in the propagation of signals from the B cell antigen rece ptor. To elucidate the functions of this kinase, we examined B cell re sponsiveness in mice engineered to lack the hematopoietic isoform of p 59(fyn). Remarkably, antigen receptor signaling was only modestly defe ctive in fyn(Tnull) B cells. In contrast, signaling from the interleuk in (IL)-5 receptor, which ordinarily provides a comitogenic stimulus w ith antiimmunoglobulin, was completely blocked. Our results document t he importance of p59(fynT) in IL-5 responses in B cells, and they supp ort a general model for cytokine receptor signal transduction involvin g the simultaneous recruitment of at least three families of PTK.