Isolation of HLA-DR-naturally presented peptides identifies T-cell epitopes for rheumatoid arthritis

Abstract

ObjectiveRheumatoid 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.MethodsHLA-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.ResultsWe 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.ConclusionsWe 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.

Development and validation of a novel criterion of histologic healing in ulcerative colitis defined by inflammatory cell enumeration in lamina propria mucosa: A multicenter retrospective cohort in China

“…[44] Moreover, CD40L, a T cell activation marker, has been identified as a significant indicator of histological activity in IBD, similar to its heightened expression in CD4 + T cells of patients with rheumatoid arthritis. [45] Currently, histological healing in UC has been defined as the normalization of the microscopic image of the colonic mucosa. [46] However, a standardized and uniform system for grading intestinal mucosal inflammation is still lacking and to date, approximately 30 different histologic scoring systems for UC have been described but have never been fully validated currently, [47,48] which brings massive conundrums in clinical practice.…”

“…[ 44 ] Moreover, CD40L, a T cell activation marker, has been identified as a significant indicator of histological activity in IBD, similar to its heightened expression in CD4 + T cells of patients with rheumatoid arthritis. [ 45 ]…”

The Search for the Pathogenic T Cells in the Joint of Rheumatoid Arthritis: Which T-Cell Subset Drives Autoimmune Inflammation?

“…After the discovery of ACPA, most studies examined synovial T-cell reactivity to citrullinated proteins, including tenacin-C [ 69 ], alpha-enolase [ 70 ], and type II collagen [ 71 ]. In the latest one, Maggi et al isolated a peptide/HLA-DR complex from the synovial tissue of RA patients and found 37 native and 6 citrullinated peptides, among which 6 peptides were able to stimulate CD4 T cells in the PB of RA patients in vitro [ 72 ]. Although there have been many studies on the antigen specificity of PB T cells in RA, T cells that induce inflammation locally in the joint and those that help B cells in APCA production in lymphoid organs do not necessarily recognize the same antigen.…”

“…Although there have been many studies on the antigen specificity of PB T cells in RA, T cells that induce inflammation locally in the joint and those that help B cells in APCA production in lymphoid organs do not necessarily recognize the same antigen. Nevertheless, citrullinated-peptide-specific CD4 T cells, even those in PB, mostly belong to the Th1 subset [ 72 , 73 , 74 ], suggesting their proinflammatory roles. At present, it is unknown whether Tph cells also recognize citrullinated protein antigens, although the autoreactivity of Tph cells in RA joints has been suggested, as described above.…”