Single-cell RNAseq analysis reveals loss of splenic mouse and human EB macrophages in HMOX-1^–/– HIS mice. Mouse and human CD45⁺ cells were purified by positive magnetic isolation from hHSC-engrafted HMOX-1^–/– and HMOX-1^+/+ MSRG47 mice. Mouse and human CD45⁺ cells were individually analyzed by single-cell RNAseq and UMAPs shown for mouse CD45⁺ cells (A) and human CD45⁺ cells (B). Tables to the right of the UMAPs show changes in specific leukocyte subsets between HMOX-1^–/– (KO) and HMOX-1^+/+ (WT). KO, knockout; UMAP, uniform manifold approximation and projection.