Role of BCGFII in the differentiation to antibody secretion normal and tumor B cells.

This report describes the effects of B cell growth factor (BCGFII) and other lymphokines in the differentiation of normal and tumor B cells. We compared BCL1 tumor B cells, normal B cells giving rise to a polyclonal response without the intentional addition of antigen, and an antigen-driven, SRBC-specific response. BCL1 tumor B cells gave maximum PFC responses when partially purified BCGFII was added or when suboptimal doses of BCGFII were mixed with one of several putative terminal differentiation factors we call B cell differentiation factors BCDF. IFN-gamma was not active as any of these factors. Maximum polyclonal responses of B cells were seen when either IL 2 or BCGFII were mixed with BCDF. In contrast, SRBC-specific responses showed a strict requirement for IL 2, and BCGFII and BCDF synergized with IL 2 to give a maximum response. The involvement of BCGFII in all of these responses suggests that BCGFII acts as a growth factor for a population of B cells that has differentiated much of the way towards Ig secretion, and that many B cells become responsive to this growth factor. In addition, the fact that different lymphokine requirements were seen in the different experimental systems raises the possibility that there are multiple pathways to Ig secretion, and suggests that different subpopulations of B cells defined either by different lineages or by different stages of development within a single lineage have requirements for distinct lymphokines that regulate their growth and differentiation.