Innate and cell-mediated immune responses to Cryptosporidium parvum.

Cryptosporidium parvum has gained much attention as a major cause of diarrhea in the world. Knowledge of the host immune mechanisms responsible for the clearance of this parasite from the gastrointestinal tract may prove to be vital for successful therapeutic treatment of cryptosporidiosis, particularly in the immunodeficient host. This chapter focuses on the innate and cell-mediated immune mechanisms associated with resistance to and resolution of a C. parvum infection. Much of the work in these areas is still in its infancy. Despite this, general consensus supports a role for interferon-gamma (IFN gamma) in mediating the initial resistance to C. parvum, although the mechanism by which this cytokine imparts resistance is unclear. It is also generally agreed that CD4+ T lymphocytes are required for the resolution of both acute and chronic cryptosporidiosis. However, the effector mechanism is again unclear. Several studies suggest that IFN gamma may also be involved in the resolution of cryptosporidiosis. However, the extent to which this cytokine is involved in the actual resolution of infection has been debated. Less extensive studies investigating the participation of other cells and cytokines in the innate and cell-mediated immune responses to C. parvum are also discussed.