Effects of dehydroepiandrosterone in immunosuppressed rats infected with Cryptosporidium parvum.

Cryptosporidium parvum is a coccidian parasite that causes diarrheal disease in animals and humans. Severe cryptosporidial infections were noted in young adult rats immunosuppressed with the glucocorticosteroid dexamethasone (DEX). B-cell and T-cell responses to the mitogens lipopolysaccharide and concanavalin A, respectively, were depressed in the DEX-treated rats. In addition, DEX treatment suppressed serum IgG levels, in vitro IgG production, and natural killer cell activities. Previous results have shown that DEX-immunosuppressed rats treated with dehydroepiandrosterone (DHEA) exhibit significant reductions in cryptosporidiosis as determined by monitoring oocyst shedding in the feces and parasite colonization of the small intestine. Results from this study indicated that B- and T-cell responses to their respective mitogens, serum IgG levels, and in vitro IgG production were greater in DHEA-treated immunosuppressed rats than in untreated DEX-immunosuppressed rats infected with C. parvum. Similar results were demonstrated in DHEA-treated versus normal control rats infected with C. parvum. These results suggest that the effects of DHEA in reducing cryptosporidiosis are the result of a potentiation of the immune system in the immunosuppressed rats.