ONTOGENY IS A CRITICAL DETERMINANT OF NATURAL KILLER CELL POTENTIAL AND FUNCTION

Abstract

The derivation of natural killer (NK) cells from human pluripotent stem cells (hPSCs) is an exciting alternative for adoptive immunotherapy strategies in the treatment of cancer. While NK cells are component of the embryonic hematopoietic repertoire, their ontogenic origins remain unclear. During mammalian embryogenesis, hematopoietic development in the early yolk sac consists of the (HSC)-independent primitive and erythro-myeloid progenitor (EMP) hematopoietic programs. Neither population is known to harbor lymphoid potential. As we previously observed NK cell development from extra-embryonic-like progenitors derived from hPSCs, we asked whether a yolk sac-derived program possesses NK cell potential. Surprisingly, we determined that EMPs isolated from the yolk sacs of E9.5 mouse embryos harbor robust NK cell potential. Further, these NK cells exhibited a potent degranulation response following stimulation, making them functionally distinct from HSC-derived NK cells. In parallel studies of hPSCs differentiated as previously described, we found that extra-embryonic-like CD34+ myeloid progenitors, similar to murine EMPs, give rise to NK cells that are biased for cytolytic degranulation. In contrast, hPSC-derived CD34+ lymphoid progenitors give rise to NK cells that are phenotypically similar to those derived from cord blood, since both exhibit a poor degranulation response but robustly produce inflammatory cytokines. Collectively, our studies in mouse embryos and human PSCs point to a novel, hematopoietic stem cell (HSC)-independent origin of embryonic NK cells that differ functionally from HSC-derived NK cells. These findings not only identify a myeloid origin to embryonic NK cells, but also have important implications for the design of hPSC-derived NK cell-based therapeutics.