Reactivity profile of a panel of anti-CD20 mAbs with the rituximab-specific peptides. Fifty microliters of PBS solution containing anti-CD20 mAb (2.5 μg/mL) was added to wells of a 96-well microtiter plate previously coated with rituximab-specific peptide. After a 4-hour incubation at 25°C, wells were washed and mAb-peptide interaction was detected by the addition of HRP-conjugated xeno-antibodies to the Fc portion of human IgG (to detect rituximab [RIT] and infliximab [INF]) or mouse IgG (to detect the remaining anti-CD20 mAb). Binding of mAb HC-10 to rituximab-specific peptides, and of Qp1a peptide with anti-CD20 mAb, included as negative controls.