Decellularized extracellular matrix (ECM) biomaterials derived from native tissues and organs are widely used for tissue engineering and wound repair. To boost their regenerative potential, ECM biomaterials can be functionalized via the immobilization of bioactive molecules. To enable ECM functionalization in a chemoselective manner, we have recently reported an effective approach for labeling native organ ECM with the click chemistry-reactive azide ligand via physiologic post-translational glycosylation. Here, using the rat lung as a model, we provide a detailed protocol for in vivo and ex vivo metabolic azide labeling of the native organ ECM using N-Azidoacetylgalactosamine-tetraacylated (Ac4GalNAz), together with procedures for decellularization and labeling characterization. Our

Immune tolerance and response are both largely driven by the interactions between the major histocompatibility complex (MHC) expressed by antigen presenting cells (APCs), T-cell receptors (TCRs) on T-cells, and their cognate antigens. Disordered interactions cause the pathogenesis of autoimmune diseases such as type 1 diabetes. Therefore, the identification of antigenic epitopes of autoreactive T-cells leads to important advances in therapeutics and biomarkers. Next-generation sequencing methods allow for the rapid identification of thousands of TCR clonotypes from single T-cells, and thus there is a need to determine cognate antigens for identified TCRs. This protocol describes a reporter system of T-cell activation where the fluorescent reporter protein ZsGreen-1 is driven by nuclear