c-kit expression in CD19⁻ progenitors is inversely related to B-lymphoid differentiation potential in short-term culture. The percentage of TdT⁺ cells from different progenitor sources expressing each differentiation marker after culture is indicated (mean ± SEM, n = 4 to 5 for CD19 and CD34 and n = 3 to 5 for CD10). The % CD10⁺ and CD19⁺ cells from all three populations was significantly different (P < .05, t-test). The % CD34⁺ cells from the c-kit⁻/CD19⁺ fraction was significantly different versus c-kit⁺/CD19⁻ (P < .05, paired t-test). The % CD34⁺ cells from c-kit⁺/CD19⁻ and c-kit⁻/CD19⁻ fractions was not significantly different.