ABSTRACT
The protection against L. major is dependent on the stimulation of an anti-leishmanial T helper 1 [Th1] response and the production of interferon-gamma [IFN-gamma]. BALB/c mice develop a Th2 response and fatal infection with Leishmania major. Strategies that boost IL-12 production have shown to be protective. The innate response to Listeria monocytogenes is associated with IL-12 production. The co- infection of BALB/c mice with L. Monocytogenes attenuates the course of L. Major infection. In this study, 8-16 weeks old female BALB/c mice were used. The lesion sizes were smaller and co-infected mice out-survived the controls injected with L. major alone. The parasite load was reduced at the site of injection, in draining lymph nodes [LN] and spleen. During the first week of infection, in vitro Leishmania re-stimulated LN cells from co-infected mice produced higher levels of IFN-7 and undetectable levels of IL-4 compared with the controls. Significant IL-4 mRNA expression was detected in LN cells of the controls, but not in the co-infected mice