CD81 is expressed on EBI macrophages and functionally required to overcome anemic stress. (A) Heat map showing the average expression levels of DEGs of cells from Vcam1+ macrophages in PHZ and BLD conditions, respectively. (B) Violin plots comparing the differences in selected gene expression levels in Vcam1– and Vcam1+ macrophages from NT, PHZ, and BLD conditions, respectively. (C) Flow cytometry analysis showing the expression of CD81 in Vcam1+ and Vcam1– macrophages, respectively. (D) Coexpression of CD81 with F4/80 and Vcam1 on EBI macrophages in steady state BM, as well as spleen under PHZ and BLD conditions, as demonstrated by Amnis ImageStream. (E) Schematic illustration of experiment to validate the function of CD81 in erythroid recovery from BLD stress. CD81 blocking antibody (anti-CD81) was administered into BLD-treated mice. (F) Comparison of spleen morphology with or without CD81 blockade under BLD conditions (n = 3). (G) Peripheral blood analysis in mice subjected to BLD stress with and without CD81 blockade (n = 5). (H) Schematic illustration of experiment to validate the function of CD81 in erythroid recovery from PHZ stress. CD81 blocking antibody (anti-CD81) was administered into PHZ-treated mice. (I) Comparison of spleen morphology with or without CD81 blockade under PHZ conditions (n = 3). (J) Peripheral blood analysis in mice subjected to PHZ stress with and without CD81 blockade (n = 5). For all quantification, means ± SEMs; ∗ P < .05; ∗∗ P < .01 by t test. HCT, hematocrit; HGB, hemoglobin; NT, no treatment.