Suppression of antibody responses by Toxoplasma infection in mice.

The immunosuppression elicited by Toxoplasma infection was proved to be due to suppressor macrophages. The induction of the suppressor macrophages are regulated by both H-2-linked and -nonlinked genes. The suppressor macrophages affect the proliferating step of lymphocytes, inhibiting them to reduce helper T cells, plasma cells and memory T- and B cells. The suppressive effect is via close contact of suppressor macrophages with lymphocytes, and not mediated by prostaglandins or H2O2. The more suppressive strain of mouse had heavier parasite burden than non-suppressive mouse strain. The patterns of induction of suppressor cells by various parasitic infections were compared and discussed.