FIG. 1.

The absence of IgM significantly alters numbers of peritoneal extracellular tachyzoites during infection with virulent T. gondii. WT and IgM^−/− mice were infected i.p. with T. gondii RH strain parasites obtained from continuous in vitro culture. (A) Extracellular peritoneal parasite numbers were ascertained on day 6 of infection using a hemocytometer. (B) Survival of IgM^−/− mice compared with WT mice following infection. Results are the mean + standard deviation of three to five mice/group and are representative of three separate experiments.