RESUMO
BACKGROUND: Antibiotic-Refractory Lyme Arthritis (ARLA) involves a complex interplay of T cell responses targeting Borrelia burgdorferi antigens succeeding towards autoantigens by epitope spreading. However, the precise molecular mechanisms driving the pathogenic T cell response in ARLA remain unclear. Our aim was to elucidate the molecular program of disease-specific Th cells. METHODS: Using flow cytometry, high-throughput T cell receptor (TCR) sequencing and scRNA-seq of CD4+ Th cells isolated from the joints of European ARLA patients, we aimed at inferring antigen specificity through unbiased analysis of TCR repertoire patterns, identifying surrogate markers for disease-specific TCRs and connecting TCR specificity to transcriptional patterns. RESULTS: PD-1hiHLA-DR+CD4+ effector T cells were clonally expanded within the inflamed joints and persisted throughout disease course. Among these cells, we identified a distinct TCRß motif restricted to HLA-DRB1*11 or *13 alleles. These alleles, being underrepresented in North American ARLA patients, were unexpectedly prevalent in our European cohort. The identified TCRß motif served as surrogate marker for a convergent TCR response specific to ARLA, distinguishing it from other rheumatic diseases. In the scRNA-seq dataset, the TCRß motif particularly mapped to peripheral T helper (TPH) cells displaying signs of sustained proliferation, continuous TCR signaling, and expressing CXCL13 and IFN-γ. CONCLUSION: By inferring disease-specific TCRs from synovial T cells we identified a convergent TCR response in the joints of ARLA patients that continuously fueled the expansion of TPH cells expressing a pathogenic cytokine effector program. The identified TCRs will aid in uncovering the major antigen targets of the maladaptive immune response. FUNDING: Supported by the German Research Foundation (DFG) MO 2160/4-1; the Federal Ministry of Education and Research (BMBF; Advanced Clinician Scientist-Program INTERACT; 01EO2108) embedded in the Interdisciplinary Center for Clinical Research (IZKF) of the University Hospital Würzburg; the German Center for Infection Research (DZIF; Clinical Leave Program; TI07.001_007) and the Interdisciplinary Center for Clinical Research (IZKF) Würzburg (Clinician Scientist Program, Z-2/CSP-30).
RESUMO
OBJECTIVE: Antinuclear antibody (ANA)-positive juvenile idiopathic arthritis (JIA) is characterized by synovial B cell hyperactivity, but the precise role of CD4+ T cells in promoting local B cell activation is unknown. This study was undertaken to determine the phenotype and function of synovial CD4+ T cells that promote aberrant B cell activation in JIA. METHODS: Flow cytometry was performed to compare the phenotype and cytokine patterns of PD-1high CD4+ T cells in the synovial fluid (SF) of patients with JIA and T follicular helper cells in the tonsils of control individuals. TCRVB next-generation sequencing was used to analyze T cell subsets for signs of clonal expansion. The functional impact of these T cell subsets on B cells was examined in cocultures in vitro. RESULTS: Multidimensional flow cytometry revealed the expansion of interleukin-21 (IL-21) and interferon-γ (IFNγ)-coexpressing PD-1high CXCR5-HLA-DR+CD4+ T cells that accumulate in the joints of ANA-positive JIA patients. These T cells exhibited signs of clonal expansion with restricted T cell receptor clonotypes. The phenotype resembled peripheral T helper (Tph) cells with an extrafollicular chemokine receptor pattern and high T-bet and B lymphocyte-induced maturation protein 1 expression, but low B cell lymphoma 6 expression. SF Tph cells, by provision of IL-21 and IFNy, skewed B cell differentiation toward a CD21low/- CD11c+ phenotype in vitro. Additionally, SF Tph cell frequencies correlated with the appearance of SF CD21low/- CD11c+CD27-IgM- double-negative (DN) B cells in situ. CONCLUSION: Clonally expanded CD4+ Tph cells accumulate in the joints of ANA-positive JIA patients and, in particular, promote CD21low/- CD11c+ DN B cell differentiation. The expansion of Tph cells and DN B cells might reflect the autoimmune response in the joints of ANA-positive JIA patients.
