T cell-derived IFN-γ is sufficient to block differentiation of eosinophils. (A) Schematic overview of the experiment. (B) Distribution of subsets of donor T cells derived from WT (CD45.1⁺) and IFN-γ^−/− mice (upper panel) and phenotype of transferred CD45.1⁺ WT T cells in the bone marrow of CD27^−/− and CD70TGxCD27^−/− host mice (lower panel; gated on CD45.1⁺ cells). CD44⁺CD62L⁻ indicates effector memory; CD44⁺CD62L⁺, central memory; and CD44⁻CD62L⁺, naive. (C) Representative plots of Siglec-F staining of bone marrow of CD27^−/− and CD70TGxCD27^−/− host mice injected with PBS, WT, or IFN-γ^−/− T cells (9 × 10⁶ cells/mouse) showing eosinophils as SSC^hiSiglec-F⁺ cells (percentages are shown). (D) Absolute numbers of eosinophils in bone marrow (one femur and one tibia) of host mice after injection with PBS or WT or IFN-γ^−/− T cells. (B-C) Data are representative of 3 mice per group are representative of 2 independent experiments. (D) Data are representative of 5 individual mice per group and are representative of 2 independent experiments. Data are mean ± SD. *P < .05; **P < .01.