The Cytometry Laboratory of the Center for Retrovirus Research requests funds to purchase the Anchored Cell Analysis and Sorting (ACAS) system, the ACAS Model 570 manufactured by Meridian Instruments, Okemos, Michigan. The ACAS system will permit investigators to analyze adherent cells in a way similar to what is now performed on nonadherent cells using flow cytometry. The ACAS 570 will be a companion instrument to the flow cytometer (Coulter EPICS 753) presently in service in the Cytometry Laboratory. Together, the two instruments will give researchers greater capability to study cell characteristics and functions under investigation in their individual projects. The ACAS 570 has several desirable capabilities that are problematic for the flow cytometer. The most obvious of these is its ability to analyze live adherent cells for parameters measurable by fluorescence without the need to prepare single cell suspensions. Detaching adherent cells often strips the membranes of the very proteins to be analyzed, and disturbs cell to cell and cell to substratum interactions. The ACAS 570 is equipped with a motor-driven stage, laser optics and fluorescence detection system and micro-computer which controls scaning and analysis of fields of cells stained in situ with fluorescent antibodies or other fluorescent probes. The computer permits repeated observations of the same cells over time. The laser system can be programmed to kill predefined cells automatically allowing subsets of cells to be isolated for future growth and characterization. The ability to characterize specific changes over time and to isolate or sort adherent cells are unique features of the ACAS that cannot be performed adequately using flow cytometry. We propose to use the ACAS 570 in a variety of projects directed at characterizing cell subsets and determining cell responses to stimuli such as virus and virus protein, hormones, DNA mutagens, drugs, toxins and cytokines. Many of the projects require the cell isolation and sorting functions of the ACAS.