The relative spatial distribution of CFU-S in the mouse spleen.

Mouse spleens were separated into white and red pulp fractions and into axial and marginal fractions for analysis of the relative concentration of hemopoietic stem cells (CFU-S) with respect to their spatial distribution in the spleen. Of the total splenic CFU-S population, 80% was in the red pulp fraction. The CFU-S concentration in this fraction was 11 times higher than in the white pulp fraction, which contained lymphoid follicles, periarteriolar sheaths, surrounding marginal zones, and occasional fragments of red pulp areas. Within the red pulp, CFU-S were spatially distributed with high concentrations in the subcapsular regions and decreasing frequency toward the median intersept of the spleen, where the CFU-S frequency was about one-fifth that found in the subcapsular area. The data suggest that marginal zones contain relatively more CFU-S than the follicles themselves.