EFFECT OF TREATMENT WITH ANTI-IgD FROM BIRTH ON THE PRODUCTION OF DIFFERENT CLASSES OF ANTIBODIES IN BALB/c MICE

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.

Physiology of IgD. III. Effect of treatment with anti-IgD from birth on the magnitude and isotype distribution of the immune response in the spleen

Continued treatment with monoclonal anti-IgD (Ig-5a) from birth in BALB/c mice causes a markedly increased responsiveness to i.v. injected dinitrophenylated ovalbumin (DNP-OVA) with Bordetella pertussis at the age of 8 weeks. The 19S plaque-forming cell (PFC)/spleen response is particularly enhanced, 6-8-fold, but all the other isotypes also show increases of 2-6-fold, including IgA and IgE. Both primary and secondary PFC responses and serum antibody titers are enhanced. After transfer of spleen cells from anti-Ig-treated mice to irradiated recipients the IgM/IgG ratio becomes similar to that of controls. In contrast, the response of anti-IgD-treated mice to i.p. immunization with either 0.2 or 100 micrograms DNP-OVA plus alum is reduced by approximately 80% for each Ig isotype except IgM and remains low upon transfer of spleen cells to recipients. It is concluded that the paucity of B cells in peripheral lymph nodes of the anti-IgD-treated mice causes the low responsiveness to i.p. immunization, but that the IgD- B cells in the spleen are quite able to respond and are, in fact, more responsive than IgD+ B cells. This increased responsiveness, together with the higher IgM/IgG ratios for all Ig isotypes and an otherwise similar order of isotype distribution (gamma 1 greater than gamma 2b greater than gamma 2a = epsilon greater than or equal to alpha) as in controls, suggests that a hyperresponsive, but less mature IgD- B cell population is selectively produced in the spleens of mice treated with anti-IgD from birth.