Leishmania donovani infects lymphocyte cell lines in vitro

Cellular interactions between Leishmania donovani parasites and human B (Daudi) and T (HUT78) cell lines were studied in vitro. Both promastigotes and amastigotes of L. donovani gained entry in approximately 60% of these cells. Transmission electron microscopy revealed the existence of intracellular amastigotes in these cell lines after infection with L. donovani. Immunophenotyping by flow cytometry confirmed the lymphocytic lineages of these cell lines. There was no evidence for intracellular replication of L. donovani in T and B cell lines. The number of intracellular amastigotes peaked on second day post-infection then gradually declined in a time-dependent manner in both the cell lines. Intracellular parasites remained more viable and transformation-competent when infection was performed with amastigotes. Attachment to the cell surface but no internalization of parasites was observed when infection was attempted on human amnion cell line WISH. Amastigotes, not the promastigotes of L. donovani induced IL-12 production by both monocyte and B cell lines.