Lack of immunoglobulin M suppression by immunoglobulin G antibody in thymectomized, irradiated, and bone marrow-reconstituted mice infected with Toxoplasma gondii

Abstract

Thymectomized, irradiated, bone marrow-reconstituted (T-deprived) mie infected with an avirulent strain of Toxoplasma gondii produced antibody titers comparable to those produced in intact syngeneic mice. Both immunoglobulin M (IgM) and IgG antibodies were produced in T-deprived animals; however, the IgM antibody remained constant in the presence of increasing amounts of IgG. In the intact animals, IgM became undetectable by day 50 postinfection as expected. Feedback inhibition of IgM by IgG seems to be dependent upon T-cells in Toxoplasma-infected mice.

Kinetics of immunoglobulin M and G responses of nude and normal mice to Trypanosoma musculi

“…This hypothesis is not only consistent with current theories on T-cell regulation of antibody production (11,13), but is also highly concordant with the mechanistic explanations of how T cells and immunoglobulin molecules interact to effect suppression of IgM responses (15,20). It is noteworthy that the lack of suppression of IgM production after the IgM to IgG shift in response to Toxoplasma gondii has also been reported in thymus cell-deprived mice (1).…”