CD37 is highly expressed on lymphoma cell lines and patient-derived samples. (A) Fluorescence-activated cell sorter (FACS) plots of tumor cell lines stained with CD37 and CD19 antibodies. NALM6, acute lymphoblastic leukemia cell line; K562 expressing CD19 and CD37, positive control; JEKO-1, MCL cell line; RAJI, Burkitt lymphoma cell line. (B) FACS plots of samples derived from 3 patients with MCL. (C) MFI of CD19 and CD37 on MCL patient’s cells. Each dot represents a separate xenograft sample (n = 3; medians shown). (D) CD19 and CD37 expression on PBMC from patients with CLL gated on CD3⁻ lymphocytes (n = 20; mean ± SD shown; ****P < .0001 by Student t test). (E) Distribution of CD19 and CD37 antigens on CLL PBMC cells. Antibodies bound per cell gated on CD3⁻ cells from each patient sample is shown. (F) Median of CD19 and CD37 antigen density is shown. CD19 range, 24 396 to 70 952; mean, 43 238; CD37 range, 8992 to 46 550; mean, 23 989. (G) CD37 immunohistochemistry in primary ALK-negative (left) and ALK-positive (right) ALCL specimens from the tissue microarray. Original magnification ×100.