Regulation of Human B Lymphocyte Activation, Proliferation, and Differentiation

This chapter discusses several specific aspects of human B cell activation. The sequence of events and the signals involved in initial B cell activation and the relationship to subsequent proliferation and the generation of Ig-secreting cells have been delineated. The functional and phenotypic heterogeneity found among B cells as well as activation requirements of specific B cell subpopulations have been examined. Finally, the roles of various cytokines including B cell growth factor (BCGF), interleukin 2 (IL-2), interferon-gamma (IFN-γ), and interleukin 1 (IL-1) in B cell responses and their temporal relationship to other B cell activation events are discussed. The nature of the signals transmitted during initial activation determined the capacity of the activated cells to respond subsequently with ongoing proliferation and differentiation. Anatomic site of origin, surface isotype expression, and activation status all play a role in determining the nature of the activation requirements and response potential of B cell subsets. Specific cytokines are presented to provide signals both during and after activation that governed the nature and magnitude of the resultant response. Regulation of human B cell responsiveness is an exquisitely controlled and remarkably complex process.