Figure 2. Unimpaired hematopoiesis in Trem1^−/− mice.

(A) Representative dot plots show the FACS-based identification of lineage-depleted (lin⁻) Sca1⁺ c-kit^hi (LSK) cells and lin⁻ Sca1⁻ c-Kit^hi myeloid progenitors in Trem1^+/+ (top panels) and Trem1^−/− (bottom panels) bone marrow (BM) following lineage depletion and depletion of lymphoid progenitors by MACS. Common myeloid progenitors (CMP), granulocyte-macrophage progenitors (GMP) and megakaryocyte/erythrocyte progenitors (MEP) were further discriminated according to their expression of FcγR and CD34. Filled histograms show TREM-1 surface expression by LSK cells, CMP, GMP and MEP progenitors from Trem1^−/− mice in comparison to Trem1^+/+ mice (lines). (B) Absolute cell numbers of total BM cells, lin⁻ BM cells, lin⁻ Sca1⁻ c-kit^hi myeloid progenitors, LSK cells, CMP, GMP and MEP and colony forming units (CFU) of hematopoietic precursors isolated from the BM of Trem1^+/+ and Trem1^−/− mice were determined as described in the Materials and Methods section. Mean values of n = 2 mice analysed are shown with error bars indicating the range. (C) Mixed BM chimeras were generated by i.v. transfer of 1∶1 mixed Trem1^+/+ x GFP^+/+ and Trem1^−/− x GFP^−/− BM cells (white circles, dotted lines) into irradiated recipient mice. As control, and to account for potential interfering effects of the GFP expression, mixed BM from Trem1^+/+ x GFP^+/+ and Trem1^+/+ x GFP^−/− mice (black circles and lines) was transferred into additional recipient mice. BM chimeras were analyzed after 10 and 31 weeks of chimerism. Neutrophils, Ly6C^hi and Ly6C^lo monocytes were identified in the peripheral blood according to the depicted gating strategy and the GFP⁻ : GFP⁺ cell ratio in the respective cell subsets was determined. Mean values of n = 4–5 mice analyzed per group are shown with error bars indicating the SEM. ns, no statistically significant difference. Data depicted in Figure 2 are representative of two independent experiments.