Expression of CD30L in leukemic cells of myeloid origin as assessed by RT-PCR (A), flow cytometry (B), and Northern blot analysis (C). (A) cDNA bulks from AML samples (FAB-M0, n = 2; M1, n = 2; M2, n = 2; M3, n = 3; M4, n = 3; M5, n = 3; M6, n = 1; and M7, n = 1) were prepared and amplified with specific primers for CD30L (upper panel) or β-actin (lower panel). The MN-60 and the BV-173 cell lines were used as positive (+) and negative (−) controls, respectively. (B) Flow cytometry analysis of representative AML cases. Cells were incubated with the anti-CD30L MoAb M80 (bold line) and an irrelevant isotype-matched mouse Ig (thin line), followed by PE-labeled goat antimouse Ig. The X- and Y-axes indicate the logarithm of the relative intensity of red fluorescence and relative cell numbers, respectively. (C) Northern blot analysis of the same AML cases shown in (B). Twenty micrograms of total RNA per lane was run on denaturated agarose gels, blotted onto nylon membranes, and hybridized with a CD30L-specific cDNA probe (upper panel) and with a GAPDH cDNA fragment (lower panel); −, negative control (BV-173 cell line); +, positive control (MN-60 cell line).