Human uterine epithelial cell secretions regulate dendritic cell differentiation and responses to TLR ligands.

The balance between immunity and tolerance in the endometrium is governed by dynamic interactions of UEC and immune cells including DC. In this study, we tested the hypothesis that soluble immune mediators secreted by UEC modulate the differentiation and functions of human DC. We found that DC differentiated with CM from polarized UEC (i.e., CM-DC) expressed significantly lower surface CD86. Upon activation with LPS or PIC, the expression of CD80, CD86, and CD83 was decreased significantly on CM-DC relative to Con-DC. Further, mRNA for TLR3, TLR4, and TLR5 was decreased significantly in CM-DC relative to Con-DC. As a functional read-out of the effect of CM on DC, we determined the following parameters: First, analysis of cytokine production showed that when compared with Con-DC, CM-DC responded to LPS or PIC stimulation with enhanced IL-10 production but undetectable IL-12p70 secretion. Second, RT-PCR analysis showed that CM-DC significantly expressed higher mRNA for IDO, an immune tolerance-promoting enzyme. Lastly, in a MLR assay, CM-DC induced significantly lower allogeneic proliferative responses compared with Con-DC. These findings indicate collectively that epithelial cells confer a tolerogenic phenotype to DC in the endometrium. Our results suggest novel cellular and molecular mechanisms for the regulation of adaptive immunity within the FRT.