TACI is expressed in monocytes from MM patients. Bone marrow MNCs from 4 healthy controls, 17 MM patients, 7 MGUS patients, and 6 AL patients were costained with anti-TACI and anti-CD14 antibodies, and analyzed by flow cytometry. Representative histograms are shown in panel A. TACI is indicated by the gray shaded curves, and isotype control staining is indicated by the open curves in CD14⁺ gated cells. (B) Surface TACI levels are indicated by ΔMFI in CD14⁺ gated cells. The solid line represents the mean value for each group.