Granulocytes in the inflammatory process of BALB/c mice infected by Leishmania amazonensis. A quantitative approach.

We used previously immunized (partially resistant) and naive (highly susceptible) BALB/c mice infected with Leishmania amazonensis for evaluating the role of granulocytes in the course of murine leishmaniasis. The animals were examined at different times post-infection and granulocytes counted in lesion tissues examined ultra-structurally. Polymorphonuclear granulocytes predominated during the early phase of infection and their number decreased with progression of infection; their number was similar in both groups during the early and intermediate phases of infection, though slightly higher in immunized animals during the late phase. Eosinophils represented approximately 10% of cells in the inflammatory infiltrate, being higher during the intermediate phase, and not differing between the groups. Another approach was the evaluation of granulocyte migration to the peritoneal cavity of susceptible BALB/c mice or resistant C57BL/6 mice under several stimuli. There was no statistically significant difference between resistant and susceptible animals in any of the treatments. Despite the influx of granulocytes to the lesion and its possible role in the initial destruction of injected Leishmania, this aspect does not seem to have an important effect on the outcome of the leishmanial infection.