Extended survival of pancreatic islet allografts in the testis of guinea-pigs.

1. Pancreatic islets, isolated from the guinea-pig pancreas by microdissection and transplanted as allografts to the testis, may survive for 11 weeks, some 5 times the maximum survival of orthotopic skin grafts. 2. Intratesticular islet cell allografts appear not to provoke a systemic immunity such as might be detected by the behaviour of a subsequent orthotopic skin allograft from the same donor. 3. Intratesticular islet cell allografts succumb (in 'second set' fashion) to a pre-existing immunity generated by a prior orthotopic skin allograft. 4. Further experimental work is necessary to determine the relative importance of graft dosage, graft antigenicity, graft site and 'graft adaptation' in determining this extended survival.