BLyS is constitutively expressed in aggressive NHL-B cells. (A) RT-PCR analysis of BLYS mRNA expression in NHL-B cell lines. (B) Immunoblot analysis of BLyS protein expression in NHL-B cell lines. (C) Immunoblot analysis of BLyS protein expression in cells from representative NHL-B patient biopsies. (D) Confocal immunofluorescence microscopic analysis of BLyS protein localization in LBCL and MCL cell lines and representative biopsy-derived LBCL and MCL patient samples. BLyS protein was stained for Cy2 (green) fluorescence, and the nuclear marker for TOPRO-3 (blue) fluorescence. (E) Flow cytometric analysis of BLyS protein on NHL-B cell surfaces. NHL (LBCL and MCL) cell lines and tumor cells from patient biopsies were stained with FITC-conjugated BLyS antibody (gray histograms) or FITC-conjugated isotype control (open histograms).