FasL is detected on B lymphocytes after HLA class II signaling. (a and b) The mean fluorescence reflecting the expression of FasL after stimulation with either 5 μg/mL L227 and goat antimouse F(ab′)2 MoAb (L227 XL), 10 μg/mL biotinylated TSST-1 and 10 μg/mL streptavidin, or 20 ng/mL PMA and 5 ng/mL ionomycin for up to 90 hours. For all of the tests, cells were fixed in a solution containing 95% ethanol with 5% acetic acid and then stained with either 2 μg/mL anti-FasL antibody N-20 or 1 μg/mL anti-FasL PE62, followed by 10 μg/mL secondary MoAb conjugated with FITC. Live and dead cells were distinguished by forward and side scatters. The background level of fluorescence in nonstimulated cells (NS) is also shown. The mean fluorescence was calculated after subtraction of the background fluorescence in the presence of the FITC-labeled secondary MoAb alone. The bars in (a) and (b) show the standard error.
