Dwarf galaxies (Mb > -18) are the most abundant objects in the Universe and are important because of their cosmological interest as tests of hierarchical theories. The formation of these galaxies is still an open question but red dwarf galaxies are preferentially located in high-density environments, pointing out a non primordial origin of these systems. Deep spectroscopic studies of galaxy clusters are needed in order to constrain dwarf galaxy formation and evolution. We have observed and analysed a nearby and massive cluster down to M *+ 6, Abell 85 (z=0.05), using the spectrograph MOS instruments VIMOS@VLT and AF2@WHT. The first and powerful tool to study the characteristics of galaxies and compare them with different density environments is the galaxy luminosity function (LF), which gives the num- ber density of galaxies of a given luminosity. The LF can be stud- ied for the global cluster, for the galaxies belonging or not to sub- structure regions, for red and blue populations and with radial dependence. The comparison of these results with those from the literature for clusters and field, allows us to conclude that, at least for Abell 85, the environment plays a major role in the na- ture of the faint-end galaxies, transforming blue dwarfs in the field into red ones in the cluster, but not in the formation of the LF slope.