Seminal fluid interacts with epithelial cells lining the female reproductive tract to induce pro-inflammatory cytokines and initiate immune adaptations for pregnancy. The plasma fraction of seminal fluid plays a key role, however sperm may also contribute. To assess the impact of sperm, CBAF1 female mice were mated with intact or vasectomised Balb/c males.
Gene expression profiles of endometrial tissue were examined by microarray (n=4/group) and qPCR (n=16-20/group). Cytokine profiles from uterine luminal fluid were assayed by Luminex assays (n=12/group). Immune cells in uterus and uterine-draining lymph nodes were assessed using immunohistochemistry (n=6/group) and flow cytometry (n=10-14/group).
Microarray data showed that mating with intact males induced greater changes in gene expression than mating with vasectomised males, with 110 genes (78 up-regulated, 32 down-regulated) differentially regulated (>1.5-FC, FDR<0.01) in intact compared to vasectomised mating. Cytokines and miRNAs associated with neutrophil recruitment including G-CSF, IP-10, IL-6, MCP-1 and miR-223-3p were amongst those specifically regulated by sperm, and immunohistochemical analysis revealed greater increases in neutrophils in the endometrium of females mated to intact compared to vasectomised males (p<0.05). Amongst T cell populations in the lymph node, total CD4+ T cells (CD4+ cells), Treg cells (CD4+CD25+Foxp3+ cells) and thymic Treg cells (CD4+CD25+Foxp3+Nrp+ cells) were not altered, but fewer antigen-specific peripheral Treg cells (CD4+CD25+Foxp3+Nrp- cells) were induced in females mated with vasectomised males, compared with intact males (p<0.05).
This study provides evidence that sperm contribute to the immune-regulatory activity of seminal fluid, and particularly are involved in neutrophil recruitment. Although neutrophils play a fundamental role in innate immune responses, recent studies have highlighted a link between neutrophils and Treg cells, raising the possibility that sperm-mediated neutrophil recruitment may contribute to antigen-specific Treg cell expansion. Current studies aim to further understanding of the association between neutrophils and Treg cells in early pregnancy and identify sperm signalling factors.