One key characteristic of certain mast cell populations is their longevity. Mast cell survival can also be promoted by Fc-receptor activation. Regulation of cell survival and apoptosis is regulated by the Bcl-2 family that consists of pro- and anti-apoptotic proteins. Depending on their relative cellular expression levels, the cells are either rescued or destined for apoptosis. To determine the regulation of mast cell survival and apoptosis, the expression of different Bcl-2 protein family members can be measured by western blot. The amount of viable versus apoptotic cells is decided by AnnexinV/propidium iodide staining, and cell lysates are prepared for western blot analysis from the appropriated time points.