Liver type 1 innate lymphoid cells develop locally via an interferon-γ–dependent loop

International audienceThe pathways that lead to the development of tissue-resident lymphocytes, including liver type 1 innate lymphoid cells (ILC1s), remain unclear. We show here that the adult mouse liver contains Lin − Sca-1 + Mac-1 + hematopoietic stem cells derived from the fetal liver. This population includes Lin − CD122 + CD49a + progenitors that can generate liver ILC1s but not conventional natural killer cells. Interferon-γ (IFN-γ) production by the liver ILC1s themselves promotes the development of these cells in situ, through effects on their IFN-γR + liver progenitors. Thus, an IFN-γ–dependent loop drives liver ILC1 development in situ, highlighting the contribution of extramedullary hematopoiesis to regional immune composition within the liver