Clarification of human blood ILC subtype interrelatedness and discovery of amphiregulin production by human NK cells shed light on HIV-1 pathogenesis

Abstract Human blood innate lymphoid cells (ILCs), which include ILCs and natural killer (NK) cells, derive from a common CD117+ILC precursor (ILCP). Yet, the relationship among the ILC subsets remains unclear. Bulk and single cell RNA-Seq and ATAC-Seq showed that blood ILC subsets cluster into ILC2s, ILCPs, a mixed cluster of CD56dim and CD56− NK cells, and a separate cluster of CD56hiNK cells that share features with both ILCs and CD56dimNK cells. In surprising contrast to mice, tissue repair protein amphiregulin was produced by human NK cells, with higher levels in CD56hiNK cells than in ILCs. Amphiregulin production by human NK cells was promoted by TCF7/WNT signaling and inhibited by TGFB1, a cytokine elevated in people living with HIV-1. Knockout of RUNX3, a WNT antagonist downstream of TGFB1, increased amphiregulin production in human NK cells. CD4+T cell depletion in people living with HIV-1, or from PBMCs in tissue culture, was associated with expansion of metabolically inert, nonfunctional CD56−NK cells. Experiments in tissue culture and in humanized mice revealed that CD56−NK cells are derived from CD56dimNK cells, and that CD4+T cell-derived IL-2 stimulates MTOR activity in CD56dimNK cells to prevent this transition. These findings clarify how ILC subsets are related to each other and provide insight into how HIV-1 infection disrupts ILC homeostasis and contributes to pathology.