Abstract Administrative Core A will provide an infrastructure for this Program Project Grant, ?New Costimulatory Pathways: Functions and Interactions?, to enable this PPG to continue to be a highly interactive and integrated program. Core A will serve as a centralized organizational structure that provides administrative support to enable the Project investigators and their personnel to focus on their experimental and scientific goals. Dr. Sharpe, Program Director of this P01 grant, will provide leadership and direction for operations of the Administrative Core, which will be based at Harvard Medical School. The Administrative Core will be responsible for carrying out the following functions: a) provide the infrastructure for overall management and co- ordination; b) facilitate and promote interactions and communication among program investigators and administrative personnel; c) maintain a Dropbox for data sharing; d) assist the Program Director and Principal Investigators with oversight of scientific, fiscal, regulatory and compliance matters, and preparation and review of yearly progress and financial reports; e) plan and coordinate External Scientific Advisory Group (ESAG) meetings; and f) facilitate sharing of tools provided by the scientific cores with PPG participants and the scientific community. To achieve these goals, Core A has the following Specific Aims. Aim 1: To provide administrative support for the PPG. Core A will provide administrative support and coordination to facilitate effective communication and interactions among all participants in the PPG projects and cores, including scheduling of regular scientific group meetings by teleconference and in person to enable PPG investigators to share data, plan experiments, and enhance their collaborations. Core A also will monitor scientific progress, establish and coordinate interactions with the ESAG, prepare and submit annual progress reports, provide fiscal oversight, ensure institutional compliance with fiscal, regulatory and scientific issues, and conflict resolution. Aim 2: To coordinate sharing of data and resources. Core A will host and manage a web-based secure portal for data sharing among the three PPG projects and two scientific cores to facilitate sharing of data in real time, planning of future experiments and collaboration, and coordinate sharing of data and resources with the research community. Through these specific Aims, we will create an Administrative Core structured to implement processes/procedures to enable the success of this highly collaborative program.