FIG. 6.

Four-color flow cytometry analysis of human leukemias for the simultaneous determination of DPP IV activity and expression of other surface molecules, as described in Materials and Methods. Gating was performed on populations almost exclusively comprised of tumor cells. Shown are two-parameter histograms with DPP IV activity (after 10 min of incubation) (right) or CD26 expression (left) in either CD4⁺, CD8⁺, or CD19⁺ cells. (A to D) Four separate T-cell acute lymphoblastic leukemias; (E) B-cell acute lymphoblastic leukemia.