For affinity sepn. filtration we developed a tailored membrane based on covalently bound receptors such as proteins like recombinant Protein A (rPA). Microfiltration membrane pores were grafted with thin layers contg. epoxy groups using photopolymn. We compared two types of membranes based on polypropylene, an unmodified one (PP) and a hydrophilized one (GHPP). With photo-grafting a similar amt. of functional groups was introduced to both membranes. We characterized the grafted membranes with respect to their hydrophilicity, total porosity and water permeability obtaining similar data for PP and GHPP. However, a different pore surface structure seemed to be present for the two types of membranes. The immobilization capacity of bovine serum albumin as a ref. protein was about 10-fold higher for the grafted PP compared to the grafted GHPP. Therefore, only the Protein A-membrane, based on unmodified PP, was further evaluated with respect to the isolation and concn. of Igs.