Deletion of Maea expressed by macrophages impairs BM EI niche. (A) Expression pattern and recombination efficiency of Csf1r-Cre in BM cells of R26TdTomato reporter mice (n = 3). (B) Expression pattern and recombination efficiency of CD169-Cre in BM cells of R26TdTomato reporter mice (n = 3). (C) RBC, hematocrit (HCT), hemoglobin (HGB), and reticulocyte (Retic) assessment of steady state control and Maea^CD169-Cre mice. (D) Total BM cellularity of control and Maea^CD169-Cre mice (n = 6). (E) Quantification of BM macrophages and EBs in Maea^CD169-Cre mice and littermate controls (n = 6). (F) Quantification of in vivo EIs (EI) in Maea^CD169-Cre and control BM (n = 4). (G) Quantification of EBs at various stages of maturation from control and Maea^CD169-Cre BM (n = 6). (H) Expression pattern and recombination efficiency of CD169-Cre in splenocytes of R26TdTomato reporter mice (n = 3). (I-K) Quantifications of total cellularity (I), macrophage (J), and EB (K) numbers in control and Maea^CD169-Cre spleens (n = 6). Data are shown as mean plus or minus SEM. *P < .05, **P < .01 by unpaired Student t test. HSC, hematopoietic stem cell; MPP, multipotent progenitors.