PT - JOURNAL ARTICLE AU - Jaxaira Maggi AU - Montserrat Carrascal AU - Lilian Soto AU - Oscar Neira AU - María C Cuéllar AU - Octavio Aravena AU - Eddie A James AU - Joaquin Abian AU - Dolores Jaraquemada AU - Diego Catalan AU - Juan C Aguillón TI - Isolation of HLA-DR-naturally presented peptides identifies T-cell epitopes for rheumatoid arthritis AID - 10.1136/annrheumdis-2021-220371 DP - 2022 Aug 01 TA - Annals of the Rheumatic Diseases PG - 1096--1105 VI - 81 IP - 8 4099 - http://ard.bmj.com/content/81/8/1096.short 4100 - http://ard.bmj.com/content/81/8/1096.full SO - Ann Rheum Dis2022 Aug 01; 81 AB - Objective Rheumatoid arthritis (RA) immunopathogenesis revolves around the presentation of poorly characterised self-peptides by human leucocyte antigen (HLA)-class II molecules on the surface of antigen-presenting cells to autoreactive CD4 +T cells. Here, we analysed the HLA-DR-associated peptidome of synovial tissue (ST) and of dendritic cells (DCs) pulsed with synovial fluid (SF) or ST, to identify potential T-cell epitopes for RA.Methods HLA-DR/peptide complexes were isolated from RA ST samples (n=3) and monocyte-derived DCs, generated from healthy donors carrying RA-associated shared epitope positive HLA-DR molecules and pulsed with RA SF (n=7) or ST (n=2). Peptide sequencing was performed by high-resolution mass spectrometry. The immunostimulatory capacity of selected peptides was evaluated on peripheral blood mononuclear cells from patients with RA (n=29) and healthy subjects (n=12) by flow cytometry.Results We identified between 103 and 888 HLA-DR-naturally presented peptides per sample. We selected 37 native and six citrullinated (cit)-peptides for stimulation assays. Six of these peptides increased the expression of CD40L on CD4 +T cells patients with RA, and specifically triggered IFN-γ expression on RA CD4 +T cells compared with healthy subjects. Finally, the frequency of IFN-γ-producing CD4 +T cells specific for a myeloperoxidase-derived peptide showed a positive correlation with disease activity.Conclusions We significantly expanded the peptide repertoire presented by HLA-DR molecules in a physiologically relevant context, identifying six new epitopes recognised by CD4 +T cells from patients with RA. This information is important for a better understanding of the disease immunopathology, as well as for designing tolerising antigen-specific immunotherapies.All data relevant to the study are included in the article. All data relevant to the study are included in the article or uploaded as online supplemental information.