An implantable system includes cells that produce and release a therapeutic agent, or agents, to a host in need. The system can include cells capable of eluting therapeutic agents in response to changing physiological conditions within a host. The system may comprise naked cells, encapsulated cells, or a mixture of non-encapsulating and encapsulated cells. The system may also comprise cells, and/or cell groups, of different origins. The implantable device may be placed intra-vascular, within bone marrow, within soft tissue, in the peritoneal cavity, or intra-hepatic, etc. The system can be comprised of a stent, or like devices. Such stents and like devices may optionally include port(s), catheter(s), and containment envelope systems for holding the above cells.