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

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Abstract
The observation that anti-Ig antibodies and T cell-replacing factor (TRF) have a synergistic effect on the stimulation of B lymphocytes to differentiate into antibody-secreting cells suggested that the crosslinking of B-cell surface Ig by antigen or anti-Ig antibody might induce the expression of a B-cell receptor for TRF. To test this possibility spleen cells from mice injected with 400-800 .mu.g of anti-IgD antibody 1-3 days before sacrifice were studied to determine if they had an enhanced capacity to adsorb TRF activity from a partially purified culture supernatant of concanavalin A-stimulated mouse spleen cells. Spleen cells from euthymic or congenitally athymic mice injected 24-30 h prior to sacrifice with either affinity-purified goat anti-mouse IgD antibody or a monoclonal allospecific anti-IgD antibody had > 100 times the TRF adsorptive capacity of spleen cells from control mice. Spleen cells from anti-IgD treated DBA/2Ha mice, which have an immune defect associated with the lack of a TRF receptor, were unable to adsorb TRF activity from concanavalin A-stimulated helper supernatants. Apparently, the crosslinking of B-cell surface Ig may induce B lymphocytes to express a receptor or receptors for TRF and enhance B-cell responsiveness to this helper factor.