sIgM engagement inhibits characteristic morphologic features of apoptosis, such as nuclear condensation and plasma membrane blebbing, and inhibits caspase activity in CLL cells.

(A-C) Stimulated CLL cells were evaluated by fluorescence microscopy after staining with DAPI. Low-power micrographs (original magnification 20x) with representative fields and high-power micrographs (insets, original magnification 100x) are included. (D) Cleavage of the broad caspase substrate PARP was determined by western blot analyses. The PARP proform (116 kd) and cleavage product (85 kd) are indicated by arrows.