CDC activity and binding levels of various antibodies directed to the B-cell surface.
(A) CDC induced by a panel of mouse IgG1 and IgG2a isotype mAbs directed at CD20, CD37, CD38, and MHCII. Daudi (▪) or EHRB (▨) cells (1 × 106/mL) were incubated with mAbs (10 μg/mL) for 15 minutes at room temperature. Normal human serum (NHS, 20% vol/vol) was then added as a source of complement and the cells incubated at 37°C for 30 minutes. Cell lysis was assessed by flow cytometry using a PI exclusion assay, and the level of CDC expressed as PI-positive cells as a percentage of total cells. The results show the means and SDs of 3 separate experiments. (B) Surface expression of CD20, CD37, CD38, and MHCII antigens on Daudi or EHRB cells. Daudi or EHRB cells (5 × 105/mL) were incubated with mAbs (10 μg/mL) for 30 minutes at room temperature, then washed and incubated with goat anti–mouse IgG F(ab′)2 FITC for 30 minutes on ice, prior to washing and analysis by flow cytometry.
