(A) Hodgkin's disease-derived cell line L428. Cultured RS cells show staining for B-B4 antibody. Cytospin preparation; APAAP immunostaining; hematoxylin counterstain. (Original magnification × 400.) (B) Flow cytometry profiles showing B-B4 expression in human HD-derived cell lines (L428, KM-H2), myeloma cell lines (LP-1, U266), and myeloid leukemia cells KG-1A. Cells were incubated with the MoAb B-B4 (closed histograms) and an irrelevant isotype-matched mouse antibody (open histograms), followed by FITC-labeled goat antimouse Ig. The X and Y axes indicate the logarithm of the relative intensity of green fluorescence and relative cell numbers, respectively.