Figure 1.

Effect of l-arginine availability on survival of Leishmania parasite inside macrophages. THP-1 monocyte-derived MΦs (A,B,C) and human monocyte-derived macrophages (hMDM) (D,E) (5 × 10⁴ cells/ml) were grown in l-arginine-supplemented and l-arginine-depleted RPMI medium followed by infection with Leishmania donovani (multiplicity of infection 1:10) for 6, 24, and 48 h. Intracellular parasites were visualized by staining the cells with Giemsa followed by optical microscopy at 100× oil immersion (A). The horizontal bar indicates 5 µm size. The parasite load was measured by counting the number of intracellular amastigotes per 100 macrophages (B,D). The rate of infection was analyzed by counting the percent infected macrophages (C,E). Each experiment was repeated three times. Each determination was made in triplicate and the values were expressed as mean ± SD for three independent experiments. Mann–Whitney U test was used to evaluate statistical significance for comparing two groups; *p < 0.05; **p < 0.005.