Objective Autoantibodies targeting histidyl–transfer RNA synthetase (HisRS; anti–Jo‐1) are common in the idiopathic inflammatory myopathies (IIMs) and antisynthetase syndrome. This study was undertaken to investigate immunity against HisRS in the blood and lungs of patients with IIM/antisynthetase syndrome. Methods Bronchoalveolar lavage (BAL) fluid, BAL fluid cells, and peripheral blood mononuclear cells (PBMCs) from patients with IIM/antisynthetase syndrome (n = 24) were stimulated with full‐length HisRS protein or a HisRS‐derived peptide (HisRS11–23). BAL fluid and PBMCs from patients with sarcoidosis (n = 7) and healthy subjects (n = 12) were included as controls. The CD4+ T cell response was determined according to levels of CD40L up‐regulation and cytokine expression using flow cytometry. Anti–Jo‐1 autoantibody responses in the serum and BAL fluid were assessed by enzyme‐linked immunosorbent assay. Lung biopsy samples from patients with IIM/antisynthetase syndrome (n = 14) were investigated by immunohistochemistry. Results In BAL fluid, CD4+ T cells from 3 of 4 patients with IIM/antisynthetase syndrome responded to stimulation with HisRS protein, as measured by the median fold change in CD40L expresssion in stimulated cells compared to unstimulated cells (median fold change 3.6, interquartile range [IQR] 2.7–14.7), and 2 of 3 patients with IIM/antisynthetase syndrome had the highest responses to HisRS11–23 (median fold change 88, IQR 27–149). In PBMCs, CD4+ T cells from 14 of 18 patients with IIM/antisynthetase syndrome responded to HisRS protein (median fold change 7.38, IQR 2.69–31.86; P < 0.001), whereas a HisRS11–23 response was present in 11 of 14 patients with IIM/antisynthetase syndrome (median fold change 3.4, IQR 1.87–10.9; P < 0.001). In the control group, there was a HisRS11–23 response in 3 of 7 patients with sarcoidosis (median fold change 2.09, IQR 1.45–3.29) and in 5 of 12 healthy controls (median fold change 2, IQR 1.89–2.42). CD4+ T cells from patients with IIM/antisynthetase syndrome displayed a pronounced Th1 phenotype in the BAL fluid when compared to the PBMCs (P < 0.001), producing high amounts of interferon‐γ and interleukin‐2 following stimulation. Anti–Jo‐1 autoantibodies were detected in BAL fluid and germinal center (GC)–like structures were seen in the lung biopsy samples from patients with IIM/antisynthetase syndrome. Conclusion The results of this study demonstrate a pronounced presence of HisRS‐reactive CD4+ T cells in PBMCs and BAL fluid cells from patients with IIM/antisynthetase syndrome as compared to patients with sarcoidosis and healthy controls. These findings, combined with the presence of anti–Jo‐1 autoantibodies in BAL fluid and GC‐like structures in the lungs, suggest that immune activation against HisRS might take place within the lungs of patients with IIM/antisynthetase syndrome.

Anti-synthetase syndrome (ASSD) is an autoimmune disease characterized by the presence of autoantibodies targeting one of several aminoacyl t-RNA synthetases (aaRSs) along with clinical features including interstitial lung disease, myositis, Raynaud’s phenomenon, arthritis, mechanic’s hands, and fever. The family of aaRSs consists of highly conserved cytoplasmic and mitochondrial enzymes, one for each amino acid, which are essential for the RNA translation machinery and protein synthesis. Along with their main functions, aaRSs are involved in the development of immune responses, regulation of transcription, and gene-specific silencing of translation. During the last decade, these proteins have been associated with cancer, neurological disorders, infectious responses, and autoimmune diseases including ASSD. To date, several aaRSs have been described to be possible autoantigens in different diseases. The most commonly described are histidyl (HisRS), threonyl (ThrRS), alanyl (AlaRS), glycyl (GlyRS), isoleucyl (IleRS), asparaginyl (AsnRS), phenylalanyl (PheRS), tyrosyl (TyrRS), lysyl (LysRS), glutaminyl (GlnRS), tryptophanyl (TrpRS), and seryl (SerRS) tRNA synthetases. Autoantibodies against the first eight autoantigens listed above have been associated with ASSD while the rest have been associated with other diseases. This review will address what is known about the function of the aaRSs with a focus on their autoantigenic properties. We will also describe the anti-aaRSs autoantibodies and their association to specific clinical manifestations, and discuss their potential contribution to the pathogenesis of ASSD.

Previous studies showed that polymerized-type I collagen (polymerized collagen) exhibits potent immunoregulatory properties. This work evaluated the effect of intramuscular administration of polymerized collagen in early and established collagen-induced arthritis (CIA) in mice and analyzed changes in Th subsets following therapy. Incidence of CIA was of 100% in mice challenged with type II collagen. Clinimorphometric analysis showed a downregulation of inflammation after administration of all treatments (P < 0.05). Histological analysis showed that the CIA-mice group had extensive bone erosion, pannus and severe focal inflammatory infiltrates. In contrast, there was a remarkable reduction in the severity of arthritis in mice under polymerized collagen, methotrexate or methotrexate/polymerized collagen treatment. Polymerized Collagen but not methotrexate induced tissue joint regeneration. Polymerized Collagen and methotrexate/polymerized collagen but not methotrexate alone induces downregulation of CD4+/IL17A+ T cells and upregulation of Tregs and CD4+/IFN-γ + T cells. Thus, Polymerized Collagen could be an effective therapeutic agent in early and established rheumatoid arthritis by exerting downregulation of autoimmune inflammation.