The cytokines secreted by the TH cells help determine the isotype produced. For TI-2 responses, presumably the cytokines are produced by cells other than T cells. CD-23 produced by follicular dendritic cells induce differentiation into plasma cells. B cells are induced following interaction with the CD40L present on activated TH cells. Overview of the development of bone marrow derived B cells.
Initial differentiation is independent of antigen.
In the periphery, development is dependent on antigen and in the absence of antigen-induced activation naive B cells die in the periphery in a few days. They are IgMmod and IgDhi at maturity. They arise continuously and throughout life from stem cells in the BM and a BM transplant will give rise to B-2 cells in recipient. They are found in LN and spleen and display a wide range of Ig V region combining sites. If not stimulated by Ag, they disappear and are replaced by different B-2 cells that continue to be generated by the BM throughout the lifetime of the animal.