MURINE LEISHMANIASIS - A PARADIGM FOR THE IMPORTANCE OF T-HELPER-1 AND T-HELPER-2 CELLS

The murine model of leishmaniosis is a prototypic example for the crit ical role played by T helper cells in immunity to pathogens. Cytokines ,such as interleukin-12 and interleukin-4, are the major regulatory fa ctors for differentiation of naive T helper cells into T helper 1 and T helper 2 cells, respectively. T helper 1 cells, which are cellular i mmune mechanisms involving gamma interferon production, are associated with protection against murine leishmaniosis. Loss of T helper 1 acti vity (i.e., reduced gamma interferon production and lack-of macrophage activation) leads to a fatal progressive course of murine leishmanios is. Knowledge of the murine model of leishmaniosis is now contributing to studies of infectious diseases in humans, livestock and companion animals. Greater insight into the pathogenesis, diagnosis and therapy of infectious diseases will be gained from the analysis of cytokine-de pendent regulation of T helper responses during infection. In particul ar, the development of prophylactic and therapeutic vaccines will bene fit significantly from these studies.