The majority of human short-lived plasma cells undergo apoptosis without activation of caspase-3. (A-B) Immunohistochemical analysis of human lymph nodes infiltrated by diffuse large B cell lymphoma (DLBCL, n = 8), myeloma (n = 7), and reactive plasmacytosis (n = 8) using an antibody that reacts specifically with active caspase-3. The bar chart shows mean percentages and SEM of apoptotic cells staining positive for active caspase-3 relative to total apoptotic cells. Asterisks indicate statistical significance. Sample tissue sections show active caspase-3 (brown staining), and arrows indicate examples of apoptotic cells with typical condensed and/or fragmented nuclei. (C) Caspase-dependent and -independent cell death in response to apoptotic stimuli in human myeloma cell lines. The myeloma lines KMS-11 and OPM-2 were treated with bortezomib (20nM), tunicamycin (5 μg/mL), and zVADfmk (100μM) for 48 hours as indicated, and cell death was assessed by staining with annexinV-FITC and propidium iodide (mean and SEM of 2 independent experiments).