Immune mechanisms in bacterial and parasitic diseases: protective immunity versus pathology.

The immunological mechanisms that contribute to resistance versus susceptibility to bacterial and parasitic infection are central to the development of improved prophylactic and therapeutic strategies. The delineation of two subsets of CD4+ T cells in the mouse that regulate these responses has provided a tremendous advance in understanding disease pathogenesis. The elucidation of protective immune mechanisms distinct from those that cause tissue damage should lead to the development of appropriate vaccines against these devastating illnesses.