Type 1 Diabetes (T1D) is a pancreas specific autoimmune disease, and insulin is a key self-antigen of T1D in both mouse model and human. Previously we reported that a protein formed by insulin and MHC class II molecule (MHC II), MHCII/B:R3 complex, is associated with T1D in animal models 1 and humans 2. We developed a monoclonal antibody specific for the IAg7-B:R3 complex of the NOD mouse, the mAb287. MAb287 recognizes IAg7-B:R3 complex expressed on cell surface. T cells expressing mAb287 on cell surface using chimeric antigen receptor technique (CAR-T cells) selectively home to pancreas and pancreatic lymph nodes (PLNs) in an adoptive transfer experiment. Thus, our animal studies show that the Insulin/MHCII epitopes exist in islets and pancreatic lymph nodes.
More and more studies indicate that the MHC/insulin peptide complex HLA-DQ8/B:R3 might be a T1D-causing antigen in T1D patients. HLA-DQ8/B:R3 specific T-cells are found in peripheral blood of T1D patients. One key question is if the findings observed from peripheral blood represent the scenario in central organs. Does the HLA-DQ8/B:R3 antigen exist in pancreas? Therefore, we developed a new antibody, mAb1E7, specific for human HLA-DQ8/B:R3. MAb1E7 antibody stains DQ8-expressing-B cells loaded with insulin peptide and spleen of insulin peptide immunized HLA-DQ8 transgenic mice by flow cytometry or immunohistochemistry approaches. In this project, we aim to investigate whether the DQ8/B:R3 epitope is expressed at central organs by staining human donor pancreata and PLNs using the highly specific mAb1E7, and identify the subtype of antigen presenting cells.
We already know that Ab1E7 stains the cell-surface HLA-DQ8/B:R3 complex of mouse organs by flow cytometry and IHC methods. Next, we will stain spleens, pancreata and PLNs of T1D or control donors requested from nPOD with Ab1E7, markers of antigen presenting cells and insulin.
Our project may disclose whether the DQ8/B:R3 complexes locate at the central organs of T1D and which subtype of antigen presenting cell(s) are responsible for its presentation; and may reveal the time window of this antigen to be detected in the development and progression of diabetes.