Mki67 ^−/− mice have specific impairment in lymphocyte-lineage compartment in the spleen despite normal reproduction, organogenesis, and mature lymphocyte cell proliferation. (A) Representative photos showing overall organ morphology of WT and Mki67^−/− mice. (B) Litter sizes of the WT (37 litters from 24 female breeders) and Mki67^−/− mice (33 litters from 12 female breeders). (C) Body weights of WT and Mki67^−/− mice at 3 wk (n = 6 for each genotype), 10 wk (n = 12 for each genotype), and 1 year (n = 5 for each genotype) of age. (D) Survival curves of WT (n = 10) and Mki67^−/− (n = 10) mice within 1 year of age. (E) Total splenocyte counts in WT (n = 3) and Mki67^−/− (n = 3) mice. (F) Gating strategy of the lymphoid and myeloid cell subsets in the spleen. (G) Quantification of the B, T, and myeloid cell subset cell numbers in the spleen of WT (n = 3) and Mki67^−/− (n = 3) mice. NK, natural killer; DC, dendritic cell. (H) Gating strategy of CTV dilution peaks in B cell cultures stimulated by anti-CD40 and IL-4. (I) Quantification of cell division in cultures of mature B cell from WT (n = 3) and Mki67^−/− (n = 4) mice. Data in E–G are representative of three independent experiments and in H and I are representative of two independent experiments. Statistical differences in B and E were determined by two-tailed unpaired t test, in C, G, and I by multiple unpaired t tests (corrected for multiple comparisons using the Holm–Sidak method), and in D by Kaplan–Meier test. Adjusted P values are shown. ns, P > 0.05.