Abstract Shared Resource 01: Analytical Cytometry (AC-SR) To advance our understanding of cancer etiology and to develop improved therapeutic approaches, it is critical for researchers to have the ability to routinely analyze and isolate discrete cell types from complex heterogeneous populations. The Analytical Cytometry Shared Resource (AC-SR) fulfills this vital function for COHCCC Members by providing services to define and isolate discrete immune system cells and cancer cells based on extracellular and intracellular protein expression, to quantify and isolate cells that express fluorescent markers, and to examine discrete cell growth states. Specific Aims for AC-SR: Aim 1. Support flow cytometry experiments for the analysis of cells and small particles. Aim 2. Maintain instrumentation for cell sorting and perform multiparameter sorting. Aim 3. Provide training support for researchers to perform independent flow cytometry analysis and sorting within the AC-SR. The AC-SR provides flow cytometry analysis and sorting instrumentation (18 analyzers, seven sorters) to support the research goals of COHCCC. The AC-SR maintains analysis instruments (7-BD LSRII/Fortessa, Cytek Aurora, BD-Symphony, 3-ThermoFisher Attune NxT, 2-ACEA Quanteons, 1-ACEA Novocyte, 2-BD C6, and BC CyAn) that enable varying degrees of parameter detection for all COH sites. A mass cytometer, Fluidigm CyTOF- Helios, and a small particle analyzer (e.g., exosome and nanoparticle; NanoSight NS300) is also available. Notably, the Aurora, Symphony, and CyTOF instruments are new since the last funding cycle. These instruments allow for high parameter experiments, enabling highly detailed analysis and interrogation of cancer cells, cancer microenvironments, and immunological responses. All analysis instruments can be operated either by researchers or by SR staff. Six cell sorting instruments (BD Aria sorters) are located across COH sites of which 4 are available for self-operation by the trained end user. COHCCC has recently purchased an additional closed system cell sorter (Miltenyi Tyto) to assist with sorting of CAR-T cell products and oncolytic viral research needs. The SR is directed by Dr. Jeremy Stark, a Professor in the Department of Cancer Genetics and Epigenetics and supported by highly qualified staff that maintain and operate the equipment while also providing training to COHCCC researchers who wish to operate AC-SR instruments independently. Members Utilization by %Revenue 2017–21: 93.6 Total (20 MCBC, 4.1 DCT, 24 CI, 45 HM, 0.26 CCPS) Publications by Members: 172, 95 with Impact Factor >10 Grants Supported: 169Total (4 ACS, 12 CIRM, 8 DoD, 6 LLS, 18 NCI of 32NIH (1P01, 88R01, 5U01))