Identification of TIMP1 as an infection-induced host factor. Related to Fig. 5. (A) Serum levels of TIMP1 in Timp1^−/− recipient mice reconstituted with BM cells infected with a retroviral vector expressing TIMP1 (MSCV-TIMP1) or a control vector (MSCV). Each group contains five mice. Symbols represent individual mice. * P < 0.05 (unpaired two-tailed Student’s t test). (B) Experimental procedure. (C) Total granulocytes in the BM of recipient mice at 2 wk after surgery. Symbols represent individual mice. ** P < 0.01; ns, P > 0.05 (unpaired two-tailed Student’s t test). (D) ELISA measurement of TIMP1 levels in the serum samples pooled from five WT or Timp1^−/− mice, as well as from five recipient mice engrafted with WT BM cells or Timp1^−/− BM cells (n = 5). (E) Sorting strategy for purifying BM CD45⁻CD31⁺ endothelial cells (including both sinusoidal [sEC] and arteriolar endothelial cells [aEC]) and CD45⁻CD31⁻ stromal cells. (F) The top UMAP plot highlights the BM stromal cell clusters, and the bottom UMAP depicts Timp1 expression levels. (G) Dot-plot presentation of Timp1 expression in the published scRNA-seq datasets (Dolgalev and Tikhonova, 2021).