Mac1⁺Gr1⁺ cells in the thymus are C/EBPαdependent and show polynuclear morphology. (A) Gating of Mac1⁺Gr1⁺ granulocytes in the adult mouse thymus and spleen. (B) Sorted Mac1⁺Gr1⁺ cells in the thymus and CD4/CD8 double-negative (DN) T-lymphocytes were cytospun and examined by Wright-Giemsa stain at 100×. Scale bars represent 10 μm. (C) The development of total CD4⁺ thymocytes and thymic granulocytes was examined in mixed chimeras of C/EBPα^F/F;VavCre⁺ fetal liver or C/EBPα^F/FVavCre⁻ control fetal liver and congenic CD45.1⁺ BM. Two mice per group were examined 10 weeks after reconstitution of lethally irradiated CD45.1⁺ hosts. (D) B cells and granulocyte development in the spleen were examined in mixed chimeras of C/EBPα^F/F;VavCre⁺ fetal liver and congenic CD45.1⁺ BM. Two mice per group were examined 8-10 weeks after reconstitution.