MISTRG mice, in which the M-CSF (CSF1), CSF2/IL3, SIRPA, THPO genes were humanized on a RAG2−/−, IL2RG−/− immunodeficient background, generate functional human monocytes, tissue macrophages, alveolar macrophages, and natural killer (NK) cells in a profile more similar to humans than other models, affording an opportunity to model multiple human immune cell types that interact with tumor cells in a human TME.10–12 However, efficiency of engraftment in most mouse strains and even the relatively efficient MISTRG mouse precludes the routine engraftment of adult HSPCs. The gene discussed is CSF1; the disease is neoplasm.