Immunopathological studies of Leishmania amazonensis infection in resistant and in susceptible mice.

Leishmania amazonensis infection was studied in mice to evaluate the evolution of leishmaniasis. The association of different methods, such as lesion kinetics, limiting dilution analysis, and immunohistochemistry, established different levels of susceptibility and resistance. Mice were arranged in 3 groups: susceptible (C57BL/10 and CBA), relatively resistant (DBA/2), and resistant (C3H.He). The histopathological analysis of primary lesions and draining lymph nodes showed a predominance of eosinophils and mast cells in the initial phase of infection in all mice. However, the most susceptible mice presented a greater number of amastigotes and higher tissue damage. The immunoglobulin analysis showed that susceptible mice produced high levels of antibodies, whereas resistant and relatively resistant mice exhibited low production of antibodies. Resistant mice showed parasite persistency in the skin and lymph nodes, suggesting that the infection in these mice can be sustained through the infection of cells such as dendritic cells, fibroblasts, and other cells present in these organs.