Ligation of CD23 on B-CLL cells increases iNOS mRNA expression. Total RNA was extracted from A549 cells, used as a positive control of iNOS expression (lane 2) and from one B-CLL cell sample, either at time 0 of the start of the culture (lane 3), or after a 16-hour incubation in the presence of 10 μg/mL of anti-CD23 MoAb 135 (lane 4), or of isotype-matched IgG₁ (lane 5). The detection by semi-quantitative RT-PCR of iNOS and β₂-microglobulin mRNA was performed using the “Image” software for the quantification of the bands after electrophoresis on a 7% acrylamide gel. Lane 1, 1-kb ladder. Results are from one experiment representative of five performed with different B-CLL cell samples. In addition, ligation of CD23 on B-CLL cells did not induce ecNOS mRNA expression (not shown).