Mobilizing dendritic cells for tolerance by engagement of immune inhibitory receptors for HLA-G.

The presence of dendritic cells (DC) in the maternal decidua has pointed to a biologic role of antigen-presenting cell in maternal-fetal interaction. The expression of immune inhibitory receptors on DC opens the intriguing possibility that these types of receptors are directly involved in maturation/activation of DC and modulate their function. We show that the triggering of the murine inhibitory receptor paired immunoglobulin-like receptor-B by cross-linking or by human leukocyte antigen (HLA)-G tetramer resulted in the modulation of DC function and prolongation of allogeneic graft survival. In addition, we found that the engagement of human inhibitory receptor ILT4 by its natural ligand, HLA-G, alters maturation of human DC. In this study, we examined the mechanisms for the modulation of antigen-presenting cells by HLA-G. These findings have established an important link between HLA-G and immune inhibitory receptor regulation in vivo and in vitro, thereby placing HLA-G in the inhibitory pathway.