Expression of CD22 and CD19 B-cell precursor ALL cell lines. (A) Surface expression of CD19 and CD22 on the ALL lines REH, SEM, NALM6-GL, KOPN8, Daudi, Raji, and on K562, as determined by directly labeled flow cytometry antibodies. (B) Quantified surface antigen expression, y-axis, for each line as listed on the x-axis. (C) CD22 site density on 110 individual patient samples of BCP-ALL, with median indicated.