Comparative FACS analysis of Ramos cells cultured in vitro (A through D) and solid tumor samples excised from SCID mice (E through H). The solid histograms show CD19 (A and E), CD20 (B and F ), CD22 (C and G), and CD40 (D and H) expression. The open histograms in (A) and (E) represent the background fluorescence due to the binding of a nonspecific antibody.