Effect of antibodies to c-kit (ACK2) or to c-fms (AFS98) on osteoclast differentiation. Experiments done according to the A schedule or B schedule of Fig 1 are summarized in (A) and (B), respectively. The period when blocking antibodies were present is indicated as + (added) or − (not added) next to the antibody used. Cultures were started by inoculating 10⁴ cells (A) and 2 × 10³ cells (B), and TRAP⁺ mononucleated (□) and multinucleated cells (▪) were counted on day 11 (A) or day 16 (B), respectively. Bars indicate means ± SD of triplicate cultures. * and ** show statistically assessed as P < .005 and P < .0005, respectively for both multinucleated and mononucleated cells.