Refillable immunoisolatory neurological therapy devices for local and controlled delivery of a biologically active factor to the brain of a patient. The devices include a cell chamber adapted for infusion with nsecretory cells and having at least one semipermeable or permselective surface across which biologically active factors secreted by the cells can be delivered to the brain. The devices also include means for introducing secretory cells into the cell chamber, and means for renewing the cells or cell medium.