MM colony formation of CD138^-/CD34^- cells following antibody-mediated cell depletion. Results are presented as a percentage of the untreated control group that was depleted of CD34⁺ and CD138⁺ cells. P < .01 for CD45⁺, CD19⁺, and CD22⁺ cell depletions calculated by Student t test comparing each group with the untreated control (n = 12). CFU indicates colony-forming units.