Induction of a B-lymphocyte receptor for a T cell-replacing factor by the crosslinking of surface IgD.

The observation that anti-immunoglobulin antibodies and T cell-replacing factor (TRF) have a synergistic effect on the stimulation of B lymphocytes to differentiate into antibody-secreting cells suggested to us the possibility that the crosslinking of B-cell surface immunoglobulin by antigen or anti-immunoglobulin antibody might induce the expression of a B-cell receptor for TRF. In order to test this possibility we studied whether spleen cells from mice injected with 400-800 micrograms of anti-IgD antibody 1-3 days before sacrifice had an enhanced capacity to adsorb TRF activity from a partially purified culture supernatant of concanavalin A-stimulated mouse spleen cells. We found that spleen cells from euthymic or congenitally athymic mice injected 24-30 hr prior to sacrifice with either affinity-purified goat anti-mouse IgD antibody or a monoclonal allospecific anti-IgD antibody had greater than 100 times the TRF adsorptive capacity of spleen cells from control mice. In contrast, spleen cells from anti-IgD treated DBA/2Ha mice, which have been shown to have an immune defect associated with the lack of a TRF receptor, were unable to adsorb TRF activity from concanavalin A-stimulated helper supernatants. This suggests that the crosslinking of B-cell surface immunoglobulin may induce B lymphocytes to express a receptor or receptors for TRF and thus enhance B-cell responsiveness to this helper factor.