Suppression of specific IgM, IgA and IgG responses in mice treated with anti-delta from birth.

In contrast to previous studies, we report that heterologous anti-delta antibodies can act as a powerful multi-class humoral immunosuppressant. Primary direct plaque-forming cell (IgM) responses of BALB/c mice injected from birth with a rabbit anti-delta antiserum were reduced to 3% of control levels against a T-dependent antigen (sheep red blood cells), and to 2% against a T-independent antigen (dextran); IgA responses against 2 intraduodenal injections of cholera toxin were reduced to 7% of control levels. Other secondary immune responses of anti-delta-suppressed mice were suppressed to a lesser degree. IgM plaque responses generated by 2 injections of sheep red cells, for example, were reduced to 50% of control levels, with reduction of the corresponding IgG response to 42%. The multi-class suppression observed indicates a clonal differentiation pathway in which the IgD+ cell develops into IgM-, IgA- and IgG-secreting cells. In light of reports that the IgD+ cell is antigen sensitive, our demonstration that IgD is capable of delivering the same sort of immunosuppressive signal in response to anti-heavy chain antibodies that IgM delivers also suggests, though it does not establish, an antigen-receptor role for IgD.