The concept of using encapsulation for the immunoprotection of transplanted cells was introduced for the first time in the 1960s. " Microencapsulated cells] might be protected from destruction and from partici- pation in immunological processes, while the enclosing membrane would be permeable to small molecules of specific cellular product which could then enter the general extracellular compartment of the recipient. For instance, encapsulated endocrine cells might survive and maintain an effective supply of hormone." (Chang, Ph.D. Thesis, McGill University, 1965; Chang et aI., Can J Physiol...