The Contractor will be required to maintain a mouse breeding/barrier facility to provide intramural investigators with inbred and congenic strains of mice not readily available from the NIAID for use in research in immunology and infectious diseases. The recent development of transgenic techniques, including gene targeting has opened up a new and exciting era in cell biology. These tools are allowing scientists to explore the importance and mechanism of action of individual gene products in vivo and to create animal models for human diseases.