CD38 and HLA-DR–mediated intracellular calcium fluxes are dependent on raft integrity. Purified monocytes were untreated (NT) or treated with 10 mM MβCD (30 minutes, 37°C), loaded with indo-1, and tested for calcium mobilization. After measurement of basal level, the following F(ab')₂ preparations of mAbs were added: CD38 mAb (IB4), HLA-DR mAb (D1.12), and CD9 mAb (PHN 200). Results are representative of at least 3 independent experiments.