IL-6 gene-targeting restores lymphopoiesis in SHIP^–/–mice. Bone marrow from wild-type, IL-6^–/–, SHIP^–/–, and IL-6^–/– SHIP^–/– mice were analyzed by flow cytometry and the results are representative of 5 separate animals. (A) B lymphocytes and myeloid cells from marrow of the various indicated animal strains were detected with anti-CD19 and anti–Mac-1 antibodies, respectively. (B) Bone marrow cells from indicated animals were depleted of Lin⁺ (CD2, CD3, CD8, CD19, B220, Mac-1, Gr1, TER-119) cells. The Lin^– fraction was analyzed for levels of c-kit and Sca-1 expression. The gates for c-kit^hiSca-1⁺, c-kit^hiSca-1^–, and c-kit^loSca-1^lo fraction are shown in each panel. The number indicates the percentage of cells falling within the indicated gate. (C) The Lin^– fraction was gated on the fraction positive for reactivity with anti–IL-7Rα antibody. IL-7Rα⁺ cells are plotted for c-kit and Sca-1 expression. The absolute cell numbers from 5 animals are summarized in Table 1. Dotted line indicates isotype control; shaded curve, IL-7Rα.