scRNAseq reveals a loss of BM B-cell progenitor populations after Abx administration. (A) UMAP visualization of scRNAseq data of ∼37 000 single cells combined from BM from mice treated for 14 days with the vehicle Ctrl or Abx cocktail in drinking water. Colors indicate general identity used for differentiating cell types, as labeled in the figure, demonstrating overall agreement between lineage identification and UMAP-based clustering. (B) Relative abundances of the cellular lineages observed from the scRNAseq data set. (C) Total murine BM cells per femur were counted on a hemocytometer in WT mice treated with Ctrl or Abx. (D) BM B-cell progenitor populations were quantified by flow cytometry in Ctrl- and Abx-treated WT mice. For panels A-D, statistical significance was determined by the Mann-Whitney U test. Data are displayed as mean ± standard error of the mean (SEM). ∗P ≤ .05; ∗∗P ≤ .01; ∗∗∗P ≤ .001; ∗∗∗∗P ≤ .0001. GMP, granulocyte-monocyte precursor; MEP, megakaryocytic-erythroid progenitor; MPP, multipotent progenitor; MSC, mesenchymal stromal cell; UMAP, uniform manifold approximation and projection.