Figure 7.

Ccl2 production increases early after BMT and plays a role in the recruitment of monocytes into the spleen. (A) Percentage of Ccl2⁺ cells in whole spleens on days 1, 2, 4, and 6 after BMT. (B) Ccl2 mRNA expression relative to 18S rRNA in sorted spleen F4/80⁺CFSE⁺ and F4/80⁺CFSE^neg cells at 1, 6, and 12 hours after lethal irradiation. (C) Flow cytometry analysis of Ccl2 production in F4/80⁺CFSE⁺ cells (red) and F4/80⁺CFSE^neg cells (blue) after BMT. (D) Representative flow cytometry diagrams of monocytes and macrophage subpopulations in Ccl2⁺ cells. (top) CD11b and Ly6C expression of Ccl2⁺cells. (bottom) F4/80 expression on Ccl2⁺CD11b^loLy6C^lo cells. (E-H) Quantitation of spleen monocytes and CD133⁺Kit⁺ SEPs in Ccl2 mutant BMT model. Ccl2^−/− (knockout, KO) or wild-type (WT) recipients were transplanted with 0.5 × 10⁶ Ccl2^−/− or WT BM cells as donors. KO → KO: Ccl2^−/− donors to Ccl2^−/− recipients; KO → WT: Ccl2^−/− donors to WT recipients; WT → KO: WT donors to Ccl2^−/− recipients; WT → WT: WT donors to WT recipients. Time points included day 8, day 10, and day 12 after BMT. n = 3-4 for each group per time point. (E-F) Total cell numbers of (E) Ly6C^hi monocytes and (F) Ly6C^lo monocytes in whole spleens. (G) Percent (left) and total cells numbers (right) of CD133⁺Kit⁺ SEPs in whole spleens. (H-I) Quantitation of spleen monocytes and CD133⁺Kit⁺ SEPs in Ccr2 mutant BMT model. WT recipients were transplanted with 0.5 × 10⁶ Ccr2^−/− or WT BM cells as donors. (H) Fold change of monocytes and (I) SEPs. n = 2-3 for each group per time point. (J) Model showing the dynamic nature of the splenic stress erythropoiesis niche.