Ligation of CD22 on the Burkitt lymphoma cell line Ramos results in apoptosis. Ramos B cells were incubated with media (Null) or with 20 μg/mL of the CD22 blocking MoAbs HB22.7 or HB22.33. Apoptosis was assessed by BRDU incoporation by DNA fragments and detecting apoptotic cells with anti-BRDU-FITC via FACS.