Incubation of MER myeloma cells with anti-CD9 mAb, ALB6, downmodulates the cell surface expression of CD9.

MER cells were incubated in the presence of ALB6 (middle panel), anti-HLA DR mAb (10 μg/mL) (lower panel), or no antibody (upper panel) for 24 hours. PWM (1%) was then added to each culture, and the cells were allowed to incubate for an additional 2 hours prior to staining. The curve on the left in each panel is IgG1 control antibody, and the curve on the right represents CD9 expression.