Preservation of Langerhans cells and macrophages in states of severe monocytopenia, such as GATA-2 and IRF8 deficiency, remains a key demonstration of the ability of human tissue macrophages to survive without continual replenishment by monocytes.31, 59 These observations were extended to the alveolar space, which contained large numbers of macrophages. This evidence concerns the gene IRF8 and Decreased total monocyte count.