Murine antibody responses to soluble proteins are generally restricted to the immunoglobulin G1 (IgG1) isotype. When mice were infected with Toxoplasma gondii Beverley and concomitantly immunized with a soluble unrelated protein antigen, a modification in the isotypic distribution of antibodies directed against this nonparasite antigen was observed, with a preferential production of IgG2a. Interestingly, when mice were immunized with a soluble protein antigen during the chronic phase (day 40) of infection with T. gondii Beverley, a similar modification in the isotypic distribution of antiprotein antibodies was observed.
Nguyen, T., Delmée, M., Bigaignon, G., Van Broeck, J., Vercammen, M., Nguyen, T., Turneer, M., Wolf, S., & Coutelier, J.-P. (1998). Acute and chronic phases of Toxoplasma gondii infection in mice modulate the host immune responses. Infection and Immunity, 66(6), 2991-2995. https://hdl.handle.net/2078.5/141784 (Original work published 1998)