Host defense to intracellular pathogens depends upon both innate and adaptive cell-mediated immune responses. Polymorphonuclear leukocytes (PMNs), which belong to the innate immune system, can be massively recruited within hours of microbial infection. In addition to their well-established effector function in innate immunity, they have been reported to secrete immunomodulatory cytokines in response to microbial stimuli in vitro, and thus may contribute to the development of antigen specific immune responses. The murine model of infection with the protozoan Leishmania major has provided crucial information concerning the role of CD4+ T cells of the Thi type in the resolution of lesions and of Th2 type in non-healing lesions. The driving events decisive for CD4+ Th1 or Th2 differentiation have been demonstrated to take place within the first hours to 3 days after infection with L. major. PMNs are recruited to the site of parasite inoculation already one hour following L. major infection and either persist in susceptible mice or decrease to 1-2 % of the cellular infiltrate 3 days after infection in resistant mice. The role of the newly migrating PMNs in the subsequent development of Leishmania-reactive T helper immune response in resistant or susceptible mice is not yet well characterized. Recent advances in this field are reviewed here.