We are requesting funds for a Cytek Development DxP 8-color upgrade for an existing BD Biosciences FACSCalibur analytical flow cytometer. The instrument to be upgraded is shared core equipment that was purchased by the Department of Microbiology and Immunology in 2005. It currently has the standard 2 laser and 4 color configurations, and thus allows up to 4 color fluorescence analyses with a relatively restricted range of fluorochromes and fluorescent proteins. This instrument is used extensively by many of the laboratories in the Department, and has been well maintained and is in excellent working order. However, because of the increasing complexity of FACS analyses done by many of the Department's investigators, this relatively simple flow cytometer is no longer able to meet current needs. A cost-effective solution to this problem is the purchase and installation of the Cytek digital 8 color upgrade requested by this application. Cytek Development is a well established company that specializes in the repair, maintenance, refurbishing and upgrading of flow cytometers. We have extensive experience with this company going back more than 5 years, and our experience with their products and services makes us confident that the proposed 8 color upgrade will be a cost- effective solution to our current need for a more advanced flow cytometer. At least 13 NIH funded faculty in the Department of Microbiology and Immunology have been identified as users for this equipment, and it is likely that additional users will be identified from laboratories run by the Department's 16 primary and 19 secondary faculty members. The use and maintenance of this equipment will be supervised by the PI of this application, Dr. Steven A. Porcelli, who is Professor in the Department of Microbiology and Immunology and overall Scientific Director of all of the shared flow cytometry resources on the Einstein campus. A technician with experience in maintaining and operating FACSCalibur flow cytometers and a number of expert consultants are available to ensure that the features of the upgraded FACSCalibur will be used to full advantage. The DxP8 8 color upgrade will provide a large group of NIH-funded microbiologists and immunologists with access to advanced flow cytometry techniques that are critically important to a wide range of basic and translational research projects.