Leishmania species: comparative ultrastructure of experimental nodules and diffuse human cutaneous lesions in American leishmaniases.

Experimental nodules of American leishmaniases were obtained by inoculating 0.1-1 x 10(5) amastigotes into the dorsum of the hindpaws of golden hamsters and of C57Bl/6J mice. The amastigotes were obtained by biopsy of lesions in six human cases of cutaneous leishmaniases and were serially maintained in golden hamsters and in a fetal calf serum-containing medium. Human nodules were obtained by biopsy from several patients with diffuse cutaneous leishmaniases, always prior to treatment. Within the same host species, no ultrastructural differences were seen in the tissue response to isolates of Leishmania mexicana, L. brasiliensis, or L. garnhami, nor were there differences between the host species in response to a particular isolate of the genus Leishmania. The typical inflammatory response was a macrophage granuloma with abundant polymorphonuclear neutrophils, some eosinophils, and plasma cells. Simple human cutaneous leishmanial lesions, as well as experimental nodules in regression, show many fibroblasts, much collagen fiber, but very few parasites. In typical lesions, parasites occurred within macrophage phagolysosomes, within distended lacunar cells, and in the intercellular spaces. Leishmaniae strongly adhered to parasitophorous vacuoles by a site of their plasma membrane directly opposite the flagellum, and the host cell cytoplasm close to the adherence site became highly vacuolated. In most cases the intra- and extracellular parasites show normal morphology, which suggest the inability of phagocytic cells to attack them.