Abstract: The invention discloses a method for selecting cells depending on their level of displaying and preferably secreting a protein of interest from a population of heterogeneously expressing cells, comprising: (a) contacting said cells with magnetic beads coated with an affinity group to the said cells, (b) mixing the said magnetic beads with the cells to capture the cells displaying/secreting the protein of interest, (c) performing at least one washing step to remove the non-captured cells, and (d) recovering the cells to which that magnetic beads have bound.