Murine MSCs protect CLL cells from spontaneous and F-ara-A–induced apoptosis. Displayed are the mean relative viabilities of CLL cells in absence or presence of murine MSCs and/or 10 μM F-ara-A at the time points shown on the horizontal axis. Results represent data for 20:1 CLL/MSC ratios and are the mean (± SEM) relative viabilities, compared with untreated controls (100%) from 5 different CLL patients for each MSC cell line. All murine MSC lines provided significant levels of protection from F-ara-A–induced apoptosis. The names of the murine MSCs are displayed above each diagram.