The absence of serum IgM enhances the susceptibility of mice to pulmonary challenge with Cryptococcus neoformans.

The importance of T cell-mediated immunity for resistance to the disease (cryptococcal disease) caused by Cryptococcus neoformans is incontrovertible, but whether Ab immunity also contributes to resistance remains uncertain. To investigate the role of IgM in resistance to C. neoformans, we compared the survival, fungal burden, lung and brain inflammatory responses, and lung phagocytic response of sIgM(-/-) mice, which lack secreted IgM, to that of IgM sufficient C57BL6x129Sv (heretofore, control) mice at different times after intranasal infection with C.