Effect of sequential sorting of CD34⁺/c-kit⁺/CD13⁻progenitor cells on the appearance of mast cells at 2 (A) and 4 (B) weeks of culture. Equal numbers (1.5 × 10⁵ cells) of c-kit⁺/CD13⁺ (+/+) and c-kit⁺/CD13⁻ (+/−) cells from the first sort were placed in culture (1st). A portion of CD34⁺/c-kit⁺/CD13⁻cells underwent a second sort (2nd) into c-kit⁺/CD13⁺ (+/+) and c-kit⁺/CD13⁻ (+/−) cells that were also placed in culture. Equal numbers (1.5 × 10⁵cells) were again plated. Results are presented as percentage of mast cells and are representative of 2 experiments separately performed, using PB cells.