3175 - Ontogeny as a Critical Determinant of Natural Killer Cell Potential and Function

Abstract

Hematopoietic development during mammalian embryogenesis is comprised of a restricted primitive program of primitive erythroid, megakaryocytic, and macrophage lineages, and a definitive program of definitive erythroid, myeloid and lymphoid potential and hematopoietic stem cell (HSC)-independent and dependent processes. Interestingly, progenitors of natural killer (NK) cells, but not B- or T-cells, have been found in the early human yolk sac, suggesting that NK cells may arise from HSC-independent sources. NK cells are innate lymphoid cells and their derivation from human pluripotent stem cells (hPSCs) is an exciting alternative for adoptive immunotherapy strategies. We have developed an hPSC differentiation method that separates primitive-like hematopoietic progenitors from HSC-independent erythro-myeloid-(T)lymphoid definitive-like potential. Using this system, we find that CD34+ cells from both populations harbor NK cell potential. Further, we find that murine E9.5 yolk sac kit+CD41+CD16/32 + erythro-myeloid progenitors give rise to NK cells ex vivo. As early as E7.5, yolk sac explants give rise to NK cells, as well as primitive and definitive erythroid progenitors. Thus, the murine yolk sac harbors NK cell potential prior to HSC emergence. NK cells from hPSC primitive-like progenitors (pNK cells) mature rapidly, are significantly more granular, and express very high levels of CD16 in comparison to their hPSC definitive-like counterparts (dNK cells) and cord blood-derived NK (cbNK) cells. Both pNK and dNK cells robustly respond to tumor targets and antibody-dependent cell-mediated cytotoxicity (ADCC) in comparison to cbNK cells. In response to K562 cells, pNK cells exhibit a 3-fold preference for cytolytic degranulation, while dNK cells are 3-fold more biased for IFNg secretion. Similarly, in response to ADCC pNK cells display 3-fold more TNFa and degranulation than dNK or cbNK cells. Collectively, these studies suggest that ontological origin is an unexpectedly important consideration in the design of hPSC-derived NK cell-based therapeutics, and raise new questions regarding the potential of early hematopoietic progenitors in the mammalian embryo.