Kinetics of the stroma-dependent hematopoiesis by primitive hematopoietic stem cells from c-fos–deficient mice. Lin⁻Sca-1⁺ cells (3 × 10²cells/well in 6-well tissue culture plate) from FL of c-fos–deficient mice (○) or control littermates (c-fos^+/+, □; c-fos^+/−, ▪) were cultured on a PA-6 stromal cell layer. The number of nonadherent cells was counted (see Fig 7 legend). The data presented are representative of three independent experiments.