CONICET | Buscador de Institutos y Recursos Humanos

Semen deposition on the genital mucosa induces an infiltrationof neutrophils to the vaginal lumen, where they rapidly outnumbersperm cells. Previous reports have shown that neutrophils interactwith sperm cells, but details are lacking regarding the impact of thisinteraction on their function. This study analyzes the influence ofspermatozoa and seminal plasma (SP) on the immune properties ofneutrophils, in paticular their ability to modulate dendritic cell (DC)phenotype and thus influence adaptive immunity.Semen samples from healthy donors were used to obtain SP andspermatozoa (purified by density gradient centrifugation). Neutrophilswere purified from blood by Ficoll-Paque centrifugation followedby dextran sedimentation. DC were obtained from monocytescultured with GM-CSF and IL-4 for 5 days. Neutrophil and DC phenotypewere analyzed by flow cytometry and cytokine productionwas assessed by ELISA.Incubation of neutrophils with sperm cells led to increased expressionof CD11b (MFI 548 +/- 34 vs 1048 +/- 51, n=5), CD66 (MFI 987+/- 144 vs 1348 +/- 151, n=5), and increased production of IL-6 (pg/ml: 701 +/- 105 vs 387 +/- 51, n=4) and TNF (pg/ml: 1038 +/- 234vs 617 +/- 42, n=4). Addition of SP in dilution 1:20 inhibited neutrophilphenotypic activation and secretion of cytokines. Interestingly,this result was mimicked by addition of prostaglandin E2 (10-6 M),a known inhibitor of neutrophil function that is abundant in SP. In asecond set of experiments, neutrophils pre-incubated with SP wereco-cultured with DCs. When compared to DCs co-cultured with controlneutrophils, DCs co-cultured with SP-treated neutrophils haddiminished production of LPS-induced IL-6 (pg/ml: 2456 +/- 344 vs677 +/- 98, n=3) and IL-1b (pg/ml: 1415 +/- 168 vs 419 +/- 84, n=3).Taken together, these results indicate that SP can block thesperm-induced activation of neutrophil and also educate them tomodulate the function of DCs, suggesting a novel immunoregulatoryfunction of SP.