Tissue-resident macrophage (MΦTR)-based immune therapies have been proposed for various diseases. However, it is still a challenge to generate a considerable amount of MΦTR that possess tissue-specific functions. Here we show that fetal liver monocytes (FLiMo) cultured with GM-CSF (also known as CSF2) rapidly differentiate into a long-lived, homogeneous alveolar macrophage (AM)-like population in vitro. CSF2-cultured FLiMo (CSF2-cFLiMo) remain the capacity to develop into bona fide AM upon

more »

... fer into Csf2ra-/- neonates and prevent development of alveolar proteinosis for at least 1 year in vivo. Compared to bone marrow-derived macrophages (BMM), CSF2-cFliMo more efficiently engraft empty AM niches in the lung and protect mice from influenza virus infection. Notably, to harness the potential of this approach for gene therapy, we restored a disrupted Csf2ra gene in FLiMo and their capacity to develop into AM in vivo, by retroviral expression of a wild-type gene. Taken together, we provide a novel platform for high-throughput genetic manipulation of AM that can be used for biological and therapeutic studies.