Flow cytometric analysis of HM1.24 expression on myeloma cells. RPMI 8226 (A) and BMMCs from patient no. 1 (B) were stained with biotin-labeled isotype control IgG or anti-HM1.24 MoAb, and PE-conjugated anti-CD38 MoAb, and then with streptavidin-RED 670. Myeloma cell regions (R) were gated for further analysis according to the side scatter (SS) profile and CD38 expression. BMMCs from patient no. 1 contained 95% of CD38⁺ myeloma cells (B). The MSFI was calculated as the ratio of mean fluorescence channel of anti-HM1.24 MoAb/control IgG.