Human normal B lymphocytes produce a growth-promoting activity for granulocyte progenitors in diffusion chamber culture after stimulation with pokeweed mitogen.

We have measured the effect of normal B lymphocytes on more primitive granulocyte progenitors (CFU-dG) clonal growth in double-diffusion chamber culture in vivo. It was found that pokeweed mitogen (PWM) stimulated B cells produce a growth-promoting activity which augments the CFU-dG--derived myeloid colony formation in a dose-dependent fashion. All colonies formed under the experimental conditions were composed exclusively of granulocytes at different stages of maturation. Unstimulated B lymphocytes did not effect the CFU-dG clonal proliferation.