Research progress in the application of MHC tetramer technology (III)

2.3. Application in autoimmune disease research

Primary biliary cirrhosis (PBC) is a chronic cholestatic liver disease of unknown etiology, characterized by progressive non-suppurative inflammatory damage of the small and medium bile ducts between the liver lobules. Serum anti-mitochondria antibody (AMA) is a specific indicator for the diagnosis of PBC. The pathogenesis of PBC is related to autoimmunity, but the efficacy of immunosuppressive agents has not been confirmed, and drug-related adverse reactions have restricted its clinical application. At present, the pathological mechanism of bile duct-specific injury is still unclear, but a large number of studies have suggested that the immune response mediated by T cells is an important mechanism of bile duct epithelial cell injury. In recent years, with the continuous development of scientific research, pathogenic T cell epitopes and their restrictive HLA molecules have been studied at the molecular level, and the main autoantigen-pyruvate dehydrogenase complex has been studied. Some T cell recognition epitopes have been identified. This is of great significance for the correct understanding of the role of antigen-specific T lymphocytes in PBC and the exploration of new treatment methods or the development of new drugs. Using tetramer technology to quantitatively detect the content of CD4+ T lymphocytes in PBC patients, the results show that the content of CD4+ T cells in the liver is 10 times, or even hundreds of times, that in the blood circulation. Theoretically, quantitative analysis of antigen-specific T cells in liver tissue lesions and in situ tracer staining will provide more and more important information for understanding the pathogenesis of PBC, so further research is needed. In short, this study has deepened people's understanding of antigen-specific T cells in PBC and laid a foundation for studying the pathogenesis of PBC.

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic erosive arthritis. Rheumatoid arthritis is characterized by synovitis, and the resulting destruction of articular cartilage and bone, which ultimately leads to joint deformities. Anti-cyclic cirullinated peptide (CCP) antibody is a polypeptide fragment of cyclic filaggrin. It is an IgG-based antibody. It has good sensitivity and specificity to RA and is positive for anti-CCP antibody. The bone destruction of RA patients is more severe than those with negative anti-CCP antibodies. To establish a method for rapid detection of low-frequency CCP-reactive T cells in peripheral blood cells by MHC class II tetramer flow cytometry. This method can be combined with anti-CCP antibodies and ELISPOT technology to further improve the sensitivity of diagnosing rheumatoid arthritis and provide a complete set of dynamic evaluation indicators for clinical research of rheumatoid arthritis. This technology also avoids many external factors affecting the in vitro culture technology used in the past, and more truly reflects the actual situation of CCP-responsive cells in the body. The research has potential application prospects, which will promote the in-depth study of the pathogenesis, early diagnosis and immunotherapy of rheumatoid arthritis and other autoimmune diseases, and promote the development of rheumatoid arthritis immunotherapy.

Regulatory T cells (Treg) are a subtype of T cells that can regulate the functions of other immune cells. Their normal physiological functions are essential for the maintenance of immune homeostasis in the body. Regulatory T cell dysfunction is closely related to the occurrence, development and treatment of many major human diseases, such as autoimmune diseases, allergic diseases, malignant tumors, and transplant rejection. Regulatory T cells can be divided into many subtypes. Among them, the most important and the most studied are the natural Foxp3+Treg (nTreg) expressing the fork head family transcription factor Foxp3 and the inducible Foxp3+Treg (iTreg). Both play a key role in regulating the immune response, especially in the prevention of autoimmune diseases and transplant rejection. As we all know, in terms of pathogenic immune response, such as autoimmune pathogenic immune response and inflammatory response, antigen-specific Treg has a better regulatory and inhibitory effect than polyclonal Treg. However, it is difficult to identify and isolate a sufficient number of antigen-specific Tregs, which limits the research on Treg regulation mechanisms and the treatment of immune diseases, and MHC II tetramer technology solves this problem well. Using MHC II tetramer, a large amount of CD4+Foxp3- with specific autoantigen glutamate decarboxylase P286-300 peptide was isolated from diabetes-resistant nonobese resistant (NOR) mice. T cell population (NR286 T cell). These Foxp3-NR286 T cells have the effect of inhibiting the proliferation of target T cells in vitro, and studies on their mechanism in vitro have shown that their regulatory function not only depends on IFN-γ and nitric oxide (NO), but also requires contact with target cells. This research provides new ideas for elucidating the Treg regulation mechanism and the treatment of type 1 diabetes.

pMHC tetramer or multimer technology relies on its own structural characteristics and has a cascade amplification effect. The tetramer technology has high sensitivity and specificity when applied to the qualitative and quantitative analysis of antigen-peptide-specific T cells, and has the advantages of less damage to cells and no need for in vitro amplification. Designing different peptides based on different epitopes of T cells-MHC tetramers can be used for epitope analysis and cell separation. At the same time, the tetramer technology can be used to detect the reaction characteristics of antigen-specific T lymphocytes and the antigenicity of specific antigen vaccines. The MHC tetramer technology provides a new means for the study of viral infections, autoimmune diseases, organ transplant rejection mechanisms, vaccine screening and evaluation, and new treatment methods.

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