Parasitic load and histopathology of cutaneous lesions, lymph node, spleen, and liver from BALB/c and C57BL/6 mice infected with Leishmania mexicana.

The course of infection, parasitic loads, and histopathology of cutaneous lesions, draining lymph node, spleen, and liver were compared in BALB/c and C57BL/6 mice over a period of 34 weeks after inoculation in footpad with promastigotes of a Leishmania mexicana reference strain. The results show that the primary footpad lesions first present a 12-week phase that develops similarly in both strains of mice. Thereafter, a cutaneous and visceral dissemination of L. mexicana parasites occurs in BALB/c mice; the latter experience an extensive breakdown of the lymphoid organ microarchitecture, whereas C57BL/6 mice succeed in eliminating the parasite infection from the lymph nodes but not from the primary cutaneous lesion, which does not heal. These results highlight marked differences between responses of key anatomical compartments controlling L. mexicana infection in BALB/c and C57BL/6 mice.