Ligation of CD23 does not elicit ecNOS expression in B-CLL cells. Purified leukemic B cells were incubated for 48 hours in the presence of medium alone (A), mouse IgG₁ (10 μg/mL) as a control (B), or anti-CD23 135 MoAb (10 μg/mL) (C). FACS analysis was then performed by indirect immunofluorescence on permeabilized cells as described in Materials and Methods. Gray line, IgG₁ isotype control; black line, anti-ecNOS MoAb.