Human CD4+ HLA-G+ regulatory T cells are potent suppressors of graft-versus-host disease in vivo

Pankratz S., Bittner S., Herrmann A.M., Schuhmann M.K., Ruck T., Meuth S.G., Wiendl H.

Abstract

CD4+ T cells expressing the immuno-tolerizing molecule HLA-G have been described as a unique human thymus-derived regulatory T (tT reg) cell subset involved in immunoregulation and parenchymal homeostasis during infectious and autoimmune inflammation. We compared properties and molecular characteristics of human CD4+ HLA-G + with those of CD4+CD25+FoxP3-expressing tTreg cells using in vitro studies of T-cell receptor (TCR) signaling, single-cell electrophysiology, and functional in vivo studies. Both tTreg populations are characterized by alterations in proximal-signaling pathways on TCR stimulation and a hyperpolarization of the plasma membrane when compared to conventional CD4+ T cells. However, both clearly differ in phenotype and pattern of secreted cytokines, which results in distinct mechanisms of suppression: While CD4+HLA-G + cells secrete high levels of inhibitory molecules (IL-10, soluble HLA-G, IL-35), CD4+CD25+FoxP3+ cells express these molecules at significantly lower levels and seem to exert their function mainly in a contact-dependent manner via cyclic adenosine-monophosphate. Finally we demonstrate that human CD4+HLA-G+ tTreg cells significantly ameliorated graft-versus-host disease in a humanized mouse model as a first proof of their in vivo relevance. Our data further characterize and establish CD4+HLA-G+ cells as a potent human tT reg population that can modulate polyclonal adaptive immune responses in vivo and thus being a promising candidate for potential clinical applications in the future. © FASEB.