Until recently, dwarf elliptical galaxies (dEs) were mostly believed to be gas-less systems, having lost their interstellar medium (ISM) through a galactic wind or through ram pressure stripping in the dense cluster environment. However, recent H$\alpha$ and HI surveys indicate that some dEs in cluster environments are able to retain part of their gas (Drinkwater et al. (2001), Conselice et al. (2001)). In a detailed observational study of the ISM of a sample of Fornax dEs, we detected genuine dEs containing warm and cold gas (De Rijcke et al. (2003), Michielsen et al. (2004), Buyle et al. (2005)).

Using an N-body/SPH code, we explore the two gas-removing scenarios in order to assess their efficiency in removing the ISM from dEs. We simulated dEs subjected to ram pressure stripping by the intracluster medium (ICM) and found that, while small dEs are instantaneously stripped, more massive dEs are able to retain part of their ISM over long time-scales. Isolated dEs on the other hand are expected to lose their gas through a galactic wind. Our simulations show that supernova explosions can blow (super)bubbles in the ISM, thereby ejecting part, though not all, of the ISM.