SUSCEPTIBILITY OF MAJOR HISTOCOMPATIBILITY COMPLEX (MHC) CLASS I-DEFICIENT AND MHC CLASS II-DEFICIENT MICE TO CRYPTOSPORIDIUM-PARVUM INFECTION

Major histocompatibility complex (MHC) class I-deficient and MHC class II-deficient mice lack functional CD8 T cells and CD4 T cells, respec tively. These mice were evaluated for infection following oral adminis tration of 10(7) Cryptosporidium parvum oocysts. MHC class II-deficien t (but not MHC class I-deficient) mice dosed with C. parvum oocysts at 3 to 5 days of age remained infected 8 weeks postexposure. MHC class II-deficient mice exposed to C. parvum oocysts at 5 to 6 weeks of age were significantly more susceptible to infection than control mice (P < 0.0001).