Engraftment of MM CD138^- cells in NOD/SCID mice. (A) Flow cytometric evaluation of murine bone marrow from animals injected with CD138^-/CD34^- or CD138⁺/CD34^- cells from a single patient. (B) Serum human immunoglobulin levels measured by ELISA in mice injected with CD138^-/CD34^- or CD138⁺/CD34^- cells from a single patient.