A Comprehensive HLA-DR4 MHC Class II Tetramer Platform for the Detection and Functional Validation of Post-Translational Modification Neoantigens.

Post-translational modification (PTM) neoantigens have emerged as key drivers of autoimmune inflammation. However, standardized protocols for MHC Class II tetramer preparation for the detection of such antigen-specific T cells remain limited, hindering the broader application of this important discovery. This study systematically engineered an HLA-DR4 (HLA-DRB1*04:02 and HLA-DRA*01:01) tetramer platform based on carboxyethyl-modified neoantigen ITGA2B peptide (ITG-CE), a PTM associated with autoimmune diseases (AUIDs) such as Ankylosing Spondylitis (AS). The platform provides a major histocompatibility complex (MHC) Class II tetramer associated with the PTM neoantigen and integrates modular protein construct, a controllable PTM peptide exchange strategy, and a specific T cell receptor (TCR) validation model. It can be employed to investigate PTM neoantigen presentation and CD4+ T cell auto-reactivity, providing extensive application value for future research into the mechanisms of PTM-induced AUIDs and immune monitoring.