Inhibition of M-CLL mAb 183 binding to an autoantigen on the surface of viable RAMOS B cells by soluble peptide. mAb 183 (12.5 μg/mL) was preincubated with soluble 183-adapted peptide (pep183) or scrambled peptide (pep183scr) at indicated concentrations. Percentage and mean fluorescence intensity (in brackets) of mAb 183 staining of RAMOS cells are presented in each panel. mAb 183 binding without peptide preincubation is shown for comparison.