Generation of interleukin-8 from human monocytes in response to Trichomonas vaginalis stimulation

Neutrophils are the predominant inflammatory cells found in the vaginal discharges of patients with Trichomonas vaginalis infection. We have investigated the possible role of interleukin-8 (IL-8) in the inflammatory response elicited by T. vaginalis infection. This study has shown that T. vaginalis induces blood monocytes to produce large amounts of bioactive IL- 8, mainly by membrane components of T. vaginalis (MTV). Monocyte-derived IL- 8 induced by MTV was dose and time dependent. The peak level of IL-8 was 102 ± 11 ng/ml of conditioned media (mean ± standard error; n = 5) obtained from MTV-stimulated monocytes (MTVCM) at 36 h of cultivation. With a multichamber chemotactic assay, we found an optimal neutrophil chemotaxis (177 ± 14 migrated cells) induced by MTVCM collected at 16 h of cultivation when the level of IL-8 was 42 ± 8 ng/ml. A neutralizing monoclonal antibody directed against IL-8, but not the irrelevant antibodies, significantly blocked the neutrophil chemotactic activity (decreased from 153 ± 6 to 23 ± 3 migrated cells; n = 3 [P < 0.001]) induced by MTVCM. Moreover, the maximum increase of the IL-8 mRNA level from MTV-treated monocytes was observed after a 5-h cultivation and decreased thereafter. Monocytes cocultured with MTV in the presence of a neutralizing monoclonal antibody directed against tumor necrosis factor alpha, but not against IL-1β, decreased IL-8 production by 25% (P < 0.05), indicating that the release of IL-8 in MTV-stimulated monocytes is partially dependent on tumor necrosis factor alpha. The capacity of MTV-induced monocytes to synthesize IL-8 suggests that these cells can contribute to the induction of the acute inflammatory response seen in T. vaginalis infection.