The multi-laser flow cytometer will upgrade and expand the capabilities of an existing, fully utilized Research Flow Cytometry Core Facility located at the Beth Israel Deaconess Medical Center. This Research Flow Cytometry Core Facility is staffed by a committed, trained full-time Manager who trains and supervises researchers, oversees a single laser flow cytometer and operates a dual laser fluorescence-activated cell sorter. This Core Facility, which has been operational since 1988, is now completely utilized by a multitude of diverse research groups located both within the Beth Israel Deaconess Medical Center and at adjoining institutions in the Harvard Medical School area. Based on the current needs of these many research groups, the requested additional instrumentation would enable the shared instrumentation in the Flow Cytometer Facility to provide new, presently unavailable types of analyses and would alleviate the delays now routine with the single, extensively utilized flow cytometer/cell-sorter. The requested instrumentation includes a four-laser research flow cytometer, which represents a cost effective means of enhancing the availability of research flow cytometry. The dual laser cell sorter has been upgraded for multi-parameter cell sorting, which fully utilizes its time. The requested instrument would provide multi-parameter analytic capabilities, including multi-color staining and cell cycle and calcium flux assays that are increasingly needed and yet unavailable. As a shared, dedicated multi-user research resource, the Research Flow Cytometry Facility at the Beth Israel Deaconess Medical Center has provided, and will continue to provide, research support capabilities not otherwise available. Investigators utilizing this Facility include those in many research laboratories in Departments at the Beth Israel Deaconess Medical Center, including the Departments of Medicine, Pathology, Surgery, and Neurology, and investigators at other nearby institutions, including the Children's Hospital Medical Center and the Brigham and Women's Hospital. The research studies supported by the current and planned Facility include those related to immunology, inflammation, molecular biology, cell biology, allergy, hematology, oncology, rheumatology, pulmonary diseases, gastrointestinal diseases, cardiovascular diseases, and viral infections. ? ?