IFN-γ neutralization corrects splenic atrophy and cytopenias. (A,B) Spleen and BM cellularity (on day 15) from 3 distinct experiments and comparing 3 groups of mice: wt (n = 5), IFN-γRKO hosts injected with anti–IFN-γ antibody R4-6A2 (n = 9), and IFN-γRKO hosts injected with isotype-matched immunoglobulins (IFN-γRKO without IFN-γ neutralization; n = 10). In panel A, we also show in light gray the spleen cellularity of 3 IFN-γRKO hosts injected with 70% of the maximal dose of R4-6A2 antibody (n = 3). (C) Peripheral blood leukocyte counts in wt hosts (n = 5), IFN-γRKO hosts with IFN-γ neutralization (n = 5), and IFN-γRKO hosts without IFN-γ neutralization (n = 7), compiled from 2 separate experiments. (D) Differential blood leukocyte counts. PMN, polymorphonuclear cells. All biologic replicates from (C) are represented by dots, and the mean is indicated by the bars. (E) Percentage of c-kit⁺/Sca-1⁺ cells from the Lin⁻ fraction among day 15 splenocytes. Dot plots are representative of at least 5 per group. (F) Numbers of LSK cells per spleen in IFN-γRKO recipients; 3 mice per group, one representative experiment out of 2. All histograms represent mean and SD *P < .05, **P < .01, ***P < .001.