Proliferation conditions promote intrinsic changes in NK Cells for an IL-10 response

Constitutively found at high frequencies, the role for NK cell proliferation remains unclear. Here, a shift in NK cell function from predominantly producing interferon-γ (IFN-γ), a cytokine with proinflammatory and antimicrobial functions, to producing the immunoregulatory cytokine IL-10, is defined during extended murine cytomegalovirus infection. The NK cells driven to express IL-10 in vivo acquired responsiveness to IL-12 and IL-21 for IL-10 production, but neither cytokine was required for the endogenous response. In vitro studies with IL-2 to support proliferation and in vivo adoptive transfers into murine cytomegalovirus-infected mice demonstrated that NK cell proliferation and further division enhanced the change. During infection, the responding NK cells acquired histone modifications indicative of an open IL-10 gene, and an IL-10 response was proliferation dependent ex vivo if the NK cells had not yet expanded in vivo but independent if they had. Thus, a novel role for proliferation in supporting changing innate cell function is discovered. The chromatin status of ex vivo isolated NK cells during MCMV infection was investigated by ChIP-seq on histone epigenetic marks (H3K4m3, H3K27m3, H3K36m3) on day 0, day 1.5 and day 3.5 post infection.