Activity of the mAb 5F11 in vitro (XTT-ASSAY). Indicated dilutions of the mAb 5F11 with 10-fold excess of GAH-IgG were distributed in 100-μL aliquots in 96-well plates. Target cells (2-4 × 10⁴; L540, L1236, Karpas 299) in 100-μL aliquots of complete medium were added and the plates incubated for 48 hours at 37°C in a 5% CO₂ atmosphere. Negative controls were done using the GAH-IgG mAb only together with the above-mentioned target cells and using the combination of the 5F11 and GAH-IgG on a CD30^- cell line (BL38). Cell viability relative to untreated control cultures was calculated using the following formula: (test value/untreated value) × 100. All measurements were done in triplicate and error bars represent standard deviations.