Human embryonic stem cell-extracts inhibit the differentiation and function of monocyte-derived dendritic cells

Embryonic stem cells (ESC) possess inherent properties of immune privilege with the capacity to evade allogeneic immune responses. Moreover, ESCs have been shown to prevent immune activation in response to third party antigen presenting cells in vitro and have the capacity to promote allograft survival in vivo. However, clinical use of human ESCs to treat immunological disorders may risk teratoma or ectopic tissue formation. Here, we show that cellular extracts from both human and mouse ESCs retain the immune modulatory properties of intact cells. ESC-extracts that contained 12-24 μg of total protein effectively prevented T cell proliferation in allogeneic mixed lymphocyte reactions (MLR), whereas control fibroblast extracts did not affect proliferation. Cellular mechanisms underlying hESC extract-mediated immune modulation involve the maturation of monocyte derived dendritic cells (mDC). hESC extract-treated mDCs had reduced surface expression of co-stimulatory and maturation markers CD80, HLA-DR and CD83 and secreted lower levels of IL12p40. Accordingly, hESC extract-treated DCs were found to be poor stimulators of purified allogeneic T cells compared to those DCs treated with vehicle or fibroblast extracts. Our results demonstrate that ESC extracts retain the immune modulatory properties of ESCs and for the first time demonstrates that ESC derived factors can inhibit human mDC maturation and function.