SUMMARY/ABSTRACT The Adaptive Phenotyping Core will provide advanced laboratory approaches to examine global and antigen- specific immune responses on samples generated for the HIPC Center entitled “ Systems immunology profiling of respiratory viral infections in vulnerable populations”. This core will serve both Research Projects, receiving samples from the Clinical Core and sharing high quality cellular profiles with the Data Management and Analysis Core. The Adaptive Phenotyping Core has two Specific Aims. In Specific Aim 1, the Adaptive Phenotyping Core will use spectral flow cytometry to generate high-dimensional profiling data on myeloid cells, B cells, and T cells in peripheral blood, nasal, and sputum samples. In Specific Aim 2, the Adaptive Phenotyping Core will profile antigen-specific T cells in peripheral blood using a standardized workflow including an activation-induced markers (AIM)-based assay, antibody-based barcoding, and spectral flow cytometry. The antigen-specific T cells to be examined is dependent on the project with Research Project 1 focused on allergen-specific T cells and Research Project 2 focused on cit-antigen-specific T cells, autoreactive T cells implicated in the pathogenesis of rheumatoid arthritis. Importantly, each of these antigen- specific T cell populations will be analyzed side-by-side with respiratory virus-specific T cells. The Adaptive Phenotyping Core will work closely with each of the Project and Core Leads.