Influence of CD1 Abs on colony formation in vitro by hematopoietic progenitor cells. Immature subsets of CFU-GM, BFU-E, and CFU-GEMM from unseparated mouse BM cells were stimulated by a combination of cytokines and mature subsets of CFU-GM and CFU-M were stimulated with single cytokines from normal (A-C) and CD1d^−/− cells (B-C) in unseparated BM plated at 5 × 10⁴ cells/mL or in Sca1⁺Lin⁻ cells plated at 250 cells/mL (D). Colonies were scored after 7 days of incubation. Results are expressed as the means ± SD of 3 plates/point. For panel A, the asterisk designates P < .001 compared with cells treated with control medium. Isotype Ab control values were not significantly different from the control group (P > .05). Significance values are shown for panel B. (C) Significant differences compared with each specific isotype control: ^aP < .001, ^bP < .002, ^cP < .004, and ^dP < .01. Other differences are not significant (P > .05).