PROJECT SUMMARY The goal of the Yale Interdisciplinary Immunology Training Program (YIITP) is to equip predoctoral trainees with the intellectual and research foundations necessary to become independent scientists/educators investigating basic mechanisms of immune system development and function. The YIITP, which is entering its 46th year, combines rigorous research training in a highly interactive environment and a thorough academic program of instruction in immunology and related disciplines with diverse opportunities for career and skill development. The program leads to the PhD and offers training in virtually all aspects of immune system development and function as well as host-microbe interactions and mechanisms by which the immune system prevents and contributes to disease. The YIITP faculty is composed of 35 immunologists with outstanding records of research accomplishment and training whose labs interact and collaborate extensively (114 collaborative publications in the last 5 years). YIITP Program Directors David Schatz and Carla Rothlin work together closely in complementary roles to direct the program and together with four additional faculty, constitute the YIITP Executive Committee, which develops new initiatives, evaluates program success based on internal and external review, and oversees trainee and YIITP faculty evaluations and appointments. The principal training entity is the Department of Immunobiology, whose graduate program has consistently been among the top-ranked immunology graduate programs in the United States. YIITP students enter Yale predominantly via application to the Immunology Track of the Biological and Biomedical Sciences (BBS) Program and are selected for YIITP appointment in year 2 based on a research focus on basic immune mechanisms. YIITP training involves formal course work, research rotations, teaching, and qualifying exam in years 1-2, with thesis research beginning in the spring of year one. A longitudinal mentoring program begins in year 1 and each student is assigned a thesis advisory committee in year 2. Training is enriched by intensive training in rigor, reproducibility, and responsible conduct of research, travel to major immunology meetings, extensive outreach, mentoring, and diversity engagement, and numerous opportunities for collaboration and interaction. YIITP trainees publish at high rates in top-level journals and over 30% in the last 10 years have won independent predoctoral fellowships. The YIITP has instituted 4 new initiatives to recruit and retain trainees from diverse backgrounds in the last 5 years, and in the last 3 years, training grant eligible (TGE) immunology applicant numbers have increased by 64% (to 144 in 2021) and those from under-represented minority (URM) groups have increased by 100% (to 32 in 2021). Fully two-thirds of matriculating TGE students in 2021 are URM. 100% of YIITP PhD recipients in the last 10 years have entered research intensive, research related, or scie...