Entamoeba histolytica produces monocyte locomotion inhibitory factor (MLIF), a pentapeptide with in vitro and in vivo anti-inflammatory properties. MLIF may interfere with leukocyte migration, disturbing the balance of pro- and anti-inflammatory cytokines secreted by CD4(+) T lymphocytes. We evaluated the effect of MLIF on expression of pro- and anti-inflammatory cytokines in human CD4(+) T lymphocytes. Regulatory cytokines [interleukin-1 beta (IL-1beta), IL-2, interferon gamma (IFN-gamma), IL-5, IL-6, and IL-10] were studied by enzyme-linked immunosorbent assay method in CD4(+)-cell supernatant fluids. Proinflammatory cytokines were produced per se by MLIF (IL-1beta, IL-2, and IFN-gamma) and also anti-inflammatory cytokines (IL-5, IL-6, and IL-10) with 1-phorbol-12 myristate-13 acetate + MLIF; the IL-1beta, IFN-gamma, IL-5 and IL-6 production was inhibited but not that of IL-10 which disclosed increase in its expression. MLIF disturbs the pro- and anti-inflammatory balance, and it induces inhibition of IL-1beta (principal proinflammatory cytokine) and increases IL-10 (prototype of an anti-inflammatory cytokine).