We propose to acquire and operate an EPICS-C cytofluorometer/cell sorter system with a Tektronics 4612 video copier for the purpose of pursuing more efficiently our ongoing studies of immunoregulatory lymphoid subsets in a variety of disease states and animal models relating to transplantation, autoimmune disease, and acute burn injury. The core user's group project a need for 80-100% machine usage. We are all engaged in NIH funded research with a growing need for this instrumentation, and this cannot be met by existing instrumentation in the area. Our group has a history of cooperative endeavors, and most of us are now located in the same laboratory area in the Brigham and Women's Hospital. The instrument chosen will permit the largescale analysis and cell sorting needed by our protocols. On occasion, certain experiments may require a dual laser machine, but this is available on a limited basis on the FACS 440 located in this hospital.