Interleukin-12 bypasses common gamma-chain signalling in emergency natural killer cell lymphopoiesis

Differentiation and homeostasis of natural killer (NK) cells relies on common gamma-chain (γc)-dependent cytokines, in particular IL-15. Consequently, NK cells do not develop in mice with targeted γc deletion. Herein we identify an alternative pathway of NK-cell development driven by the proinflammatory cytokine IL-12, which can occur independently of γc-signalling. In response to viral infection or upon exogenous administration, IL-12 is sufficient to elicit the emergence of a population of CD122(+)CD49b(+) cells by targeting NK-cell precursors (NKPs) in the bone marrow (BM). We confirm the NK-cell identity of these cells by transcriptome-wide analyses and their ability to eliminate tumour cells. Rather than using the conventional pathway of NK-cell development, IL-12-driven CD122(+)CD49b(+) cells remain confined to a NK1.1(low)NKp46(low) stage, but differentiate into NK1.1(+)NKp46(+) cells in the presence of γc-cytokines. Our data reveal an IL-12-driven hard-wired pathway of emergency NK-cell lymphopoiesis bypassing steady-state γc-signalling.