CD26 and CXCR4 expression was examined on fresh and transduced lin- cells. (A, B) Histograms showing expression of CD26 and CXCR4, respectively. Filled histograms represent expression on fresh cells; unfilled dark lines represent expression on cultured (cx) cells; unfilled light lines represent isotype (iso) controls. (C, D) Bar graphs showing fraction of cells expressing CD26 and CXCR4, respectively. *, P < 0.0001; †, P = 0.008. (E, F) Bar graphs showing MFI of CD26 and CXCR4, respectively. ‡, P = 0.02. For C-F, filled bars represent fresh cells, unfilled bars represent transduced cells. N = ≥3 independent experiments for all groups.