The Tissue Analysis Core (TAC) within the AIDS and Cancer Virus Program will process, embed, and perform microtomy on fixed tissue samples presented in ethanol. CD4 (DAB) and CD68/CD163 (FastRed) double immunohistochemistry will be performed, in which the CD68/CD163 signal “masks” the low CD4 expression found on macrophage/dendritic cells. To ensure consistency among assay batches, we have automated a major portion of the double immunohistochemistry assay using the IntelliPATH autostainer. A high-resolution digital image of each double immunohistochemistry stained sample will be generated using the Aperio ScanScope CS System. Regions of interest (ROI; 20–30) of a defined size will be highlighted on each digital image using the Aperio ImageScope software regions tool, and high-resolution images of ROIs will be generated using a custom-written software program created by the Imaging and Visualization Group that automatically extracts ROIs from the digital slide annotation layer. Finally, under the guidance of a subject matter expert, the TAC will provide comprehensive quantitative image analysis using a custom series of unique actions in Photoshop with Fovea tools to determine the percent area in each high-resolution image that is occupied by CD4+ T cells. Relevant data will be provided electronically, and a report with interpretation/conclusions will be supplied. Sufficient basic consultation with a subject matter expert is included with the service.