Splenic macrophage precursor cells from Leishmania donovani infected mice as cytotoxic effectors against pro- and amastigotes

The most important effectors of natural- as well as lymphokine-mediated cytotoxicity against microbicidal and fungal targets and protozoa such as Leishmania donovani are represented by cells of the monocyte-macrophage lineage. We recently described the bone marrow-derived macrophage precursor which is able to spontaneously and extracellularly kill protozoa of the genus Leishmania. These nonadherent, nonphagocytic macrophage precursor cells are present in the spleen of healthy mice only in a small quantity; however, high nmumbers have been isolated from the spleen of L. donovani infected mice. Macrophage precursors from spleen of diseased animals are able to kill spontaneously the promastigote as well as the amastigote form of L. donovani. the mechanism of the spontaneous leishmanicidal activity of macrophage precursor cells derived from spleens of L. donovani infected mice was investigated. This effector function could be defined in part as an antibody-dependent cellular cytotoxicity ( ADCC). In addition we assessed the role of CSFI containing L-cell donditioned supernatant at the leishmanicidal activity of these immature cells of the macrophage lineage. For that purpose, nonadherent cells from healthy mice were cocultivated with this CSFI containing medium for four days. These in vitro proliferated macrophage precursor cells from untreated mice showed an increased leishmanicidal activity. (-y-