? REAGENT CORE Recruitment and localization of leukocytes to sites of infection in inflamed tissue is a dynamic and regulated process that depends on cross talk between different cell populations, responses to specific environmental cues, and the expression of appropriate effector molecules. The overall goal of this program project is to define key molecular and cellular processes that regulate effective T cell immune responses in peripheral tissue during the initial innate inflammatory response, during effector T cell activation, and during the generation and persistence of tissue-restricted memory. In concordance with this overall goal, the goal of this reagent core is to develop reagents that will enable us to both monitor and manipulate key molecules in a spatially and temporally regulated fashion in specific cell types. The reagents developed in the core will enable all of the projects to probe the functional significance of specific intracellular and membrane-associated events that change as cells interact with other cells and within specific microenvironments in inflamed tissue. The Reagent Core has three aims: 1. To generate retroviruses expressing genetic reporters to image functional events and to manipulate expression of key proteins in T cells. We will generate retroviruses that can be used to localize and manipulate structural proteins that regulate T cell migration and ECM interactions (integrins and cytoskeletal proteins), to monitor intracellular signaling events, and to modify gene expression. 2. To generate and maintain breeding stocks of genetically modified mouse strains that tag specific leukocyte populations with different fluorescent tags. To fully understand how cellular cross talk can influence an immune response, it is necessary to define the cell populations that are present within the inflamed tissue. The goal of this aim will be to maintain a breeding colony of genetically modified mouse lines that express tissue specific fluorescent reporters to identify and distinguish T cells and different myeloid cell populations in inflamed tissue. This repository will enable investigators to ?mix and match? fluorescently tagged cells and recipient mice as they plan IV-MPM experiments 3. To create new mouse models to allow for identification and/or manipulation of key leukocyte subpopulations. In this aim we propose to generate several new animal models that are not currently available commercially or collaboratively. These will include mice that express leukocyte subpopulation- specific fluorescent tags, as described in Aim 2 and floxed alleles for integrins (Alpha 1 and Alpha E) that regulate the positioning and function of CD8 TRM cells.