I am working on isolating B cells from peripheral blood. The blood is collected and the isolation protocol is immediately started. I use a Ficoll layer and Miltenyi Biotinylated MicroBeads to isolate the B cells. I am getting appropriate and good yields immediately after the isolation, but after the overnight culture, my cell count drops a lot, and I can hardly use them for anything but phenotyping. Does anyone have suggestions to help my cells proliferate during overnight culture?