This project proposes to maintain a colony of mice bearing histocompatibility gene mutations, particular those of the H-2 complex, as a resource colony. Incipient mutant strains, currently under development, will be completed and added to the collection. Strains maintained will be systematically monitored to maintain their genetic integrity, by skin grafting and by serological typing. No further large scale screening by skin grafting, for new mutants will be carried out as part of this project. however, additional future mutants may be added as recovered from another separately funded project in which skin grafting is used to monitor the genetic integrity of the NCI mouse colonies.