Athymic mice have defective hematopoiesis with accumulation of committed progenitors in the bone marrow. (A) Total and (B) differential cell counts in normal (□) and nude (▪) mice bone marrow. Neutrophils precursor (Neut Prec), segmented neutrophil (Segm), erythroblast (Erythr), lymphocyte (Lymph), and monocyte (Monoc) counts are shown. Error bars mean SEM. (C) Distribution of SCA-1 populations in the bone marrow. BM samples stained with anti–SCA-1 and the individual lineage markers were analyzed by flow cytometry. Gated population represents SCA-1⁺Lin⁺ cells and the respective mean ± SD are indicated. (D) Estimation of erythroid (BFU-E) and myeloid progenitors/precursors (CFU-GM) in the bone marrow of control (▪) and nude (▴) mice. All data are representative of 10 to 15 animals individually analyzed, except for BFU-E (n = 5). Horizontal bars indicate the mean. (E) Flow cytometry analysis of control (left) and SCID (right) mice bone marrow. The distribution of SCA-1 populations is shown, and number of SCA-1⁺Lin⁺ cells and the respective mean ± SD are indicated (n = 5). (F) LTBMCs were prepared as described in “Materials and methods” and fed weekly with lymph node cells (LTBMC + LN). After 3 weeks of culture, the cells were harvested and stained with anti–SCA-1 and Lin (anti-CD11b + anti-Gr1). Gated population represents SCA-1⁺Lin⁺ cells, and the respective mean ± SD are indicated. Dot plots are representative of 2 independent experiments. *P < .001; **P < .03.