A method for treatment of a neurodegenerative condition in a patient comprising implanting in the patient at least one immunoisolatory vehicle comprising a corc comprising a volume of at least 1 .mu.l and at least 10.sup.4 living cells which secrete at least one biologically active product, said cells being dispersed in a biocompatible matrix comprising a hydrogel or extracellular matrix components, and an external jacket surrounding the core, the jacket comprising a biocompatible hydrogel or thermoplastic, the jacket being free of cells projecting externally thereof, said jacket having a molecular weight cutoff permitting the passage of the biologically active product from the core through the jacket.