devices and methods are disclosed to provide hybrid , modular systems for the constitutive delivery of appropriate dosages of active factor to a subject and , in some instances , to specific anatomical regions of the subject . the systems include a cell reservoir containing living cells capable of secreting an active agent , which is preferably adapted for implantation within the body of the subject and further includes at least one semipermeable membrane , whereby the transplanted cells can be nourished by nutrients transported across the membrane while at the same time protected from immunological , bacterial , and viral assault . the systems further include a pumping means , which can be implantable or extracorporeal , for drawing a body fluid from the subject into the cell reservoir and for actively transporting the secreted biological factors from the cell reservoir to a selected region of the subject .