Trichomonas vaginalis‐induced neutrophil apoptosis causes anti‐inflammatory cytokine production by human monocyte‐derived macrophages

SUMMARY Neutrophils are the predominant inflammatory cells found in the vaginal discharge of patients with a Trichomonas vaginalis infection. Neutrophils have a shorter life span than other leucocytes. Our previous study indicated that live T. vaginalis alters Mcl‐1 expression and caspase‐3 activation, thereby inducing apoptosis of human neutrophils. However, it was previously unknown that the apoptotic neutrophils brought about by T. vaginalis can influence vaginal inflammation. Thus, human monocyte‐derived macrophages (HMDM) were incubated with T. vaginalis‐induced apoptotic neutrophils. Cytokine production and phagocytosis by HMDM were evaluated by ELISA and myeloperoxidase stain, respectively. HMDM showed increased anti‐inflammatory cytokine production (IL‐10) and decreased levels of pro‐inflammatory cytokines, such as TNF‐α and IL‐6, compared with macrophages alone. Therefore, these results suggest that apoptotic neutrophils caused by T. vaginalis may lead to the resolution of vaginal inflammation by anti‐inflammatory cytokine production in the human macrophages.