Expression of FasL in native malignant plasma cells from myeloma patients. (a) Typical side light scattering profile of a BM sample from a myeloma patient stained with a PE-conjugated CD38 MoAb. The plasma cell population was defined by its unique position at a very low side light scattering profile and highest CD38 expression levels29 and gated (red circle) for further analysis. (b and c) Analysis of FasL expression in the gated plasma cell population of two patients with multiple myeloma (nos. 4 and 6, Table 2). A significant shift in fluorescence intensitiy in samples stained with the NOK-1 FasL antibody (red line) was observed when compared with samples treated with the isotype-matched control MoAbs only (black line). (d) FasL negative plasma cell sample (no. 1, Table 2).