(A) Semi-quantitative RT-PCR on RNA from human ALL cells cultured on OP9 stroma, using the primers indicated to the right. β2 microglobulin serves as control. Ramos and Jurkat; positive and negative controls respectively. (B) FACS analysis on the indicated ALL cells (P-2, BLQ-1, BLQ-11 and TXL-2) cultured on OP9 stroma using anti BAFF-R, BCMA and TACI antibodies. Ramos and Jurkat; positive and negative controls, respectively. Histograms show overlay of isotype control (black line) and receptor antibodies (gray line).