Role of CD4+ TH1- and TH2-cell-secreted cytokines in cryptosporidiosis.

Cryptosporidium parvum is now recognized as an important gastrointestinal pathogen around the world. Unfortunately, control measures for cryptosporidiosis are currently not well defined and very little is known about the immunological events relevant to the control of infection. Cytokine depletion experiments were conducted by injecting adult BALB/c mice with monoclonal antibodies directed to IL-2, IL-4, and IL-5, prior and during C. parvum infection. Faecal oocyst excretion and intestinal parasite number were monitored from day 4 to day 31 post-infection. Mice injected with monoclonal antibodies to IL-5 or IL-4/IL-5, but not IL-4 alone, harboured significantly higher numbers of both intestinal parasites and excreted oocysts. It is concluded that IL-5 complemented with IL-4 appears to be an important TH2-dependent mechanism for controlling cryptosporidiosis. Nevertheless, we suggest that cytokines secreted by both TH1 and TH2 cells may operate in concert in controlling cryptosporidiosis, triggering different functional mechanisms in a dynamic and simultaneous up- and down-regulatory fashion.