M3 muscarinic acetylcholine receptor-reactive Th17 cells in primary Sjögren's syndrome.

M3 muscarinic acetylcholine receptor (M3R) is one of the autoantigens associated with Sjögren's syndrome (SS) and is localized in exocrine glands where disease-specific inflammation occurs. The inflammatory lesion is characterized by infiltration of CD4+ T cells, including clonally expanded Th17 cells. We undertook this study to identify circulating M3R-specific Th17 cells and to determine functional properties of those cells. Using the enzyme-linked immunospot assay (ELISpot) method, we identified M3R-reactive Th17 cells in the peripheral blood of patients with primary SS (pSS). Among 10 examined pSS patients, 10 healthy subjects (HS), and 5 IgG4-related disease (IgG4-RD) patients, M3R-reactive IL-17 secreting cells were significantly increased in 5 pSS patients specifically. The most common T cell epitope, which was analyzed and confirmed by coculture of isolated CD4+ T cells with antigen presenting cells plus M3R peptides in vitro, was peptide 83-95 of M3R. Peptide recognition was partly in an HLA-DR-restricted manner, confirmed by blocking assay. M3R-reactive Th17 cells positivity correlated with higher titers of anti-M3R antibodies, whose systemic disease activity score tended to be higher. Our studies highlight the role of tissue-specific autoantigen-derived circulating Th17 cells in pSS, for which further work might lead to antigen-specific targeted therapy.

Upregulation and pathogenic roles of CCL18-CCR8 axis in IgG4-related disease.

Objectives: To determine the protein expression level, expressing cell types, and pathogenic roles of chemokine (C-C motif) ligand 18 (CCL18) and its receptor chemokine (C-C motif) receptor 8 (CCR8) in affected tissues of patients with IgG4-related disease (IgG4-RD).Methods: The protein expression levels of CCL18 in labial salivary glands (LSGs) assessed by immunofluorescence (IF) staining were compared among patients with IgG4-RD (n = 3), primary Sjögren's syndrome (pSS; n = 4), and control subjects (n = 5). CCL18 expression levels in macrophages, CD11c+ cells, B cells, and plasmacytes in LSGs were examined by double IF staining. The protein expression levels of CCR8 and expressing cells (T, B cells, and plasmacytes) in LSGs were also compared among patients with IgG4-RD, pSS, and control subjects by double IF staining. The effects of the CCL18-CCR8 axis on total IgG, IgG2, and IgG4 production by peripheral blood mononuclear cells (PBMCs) stimulated with CD40L, IL-4, IL-10, and IL-21 were examined by in vitro assays.Results: CCL18 was specifically upregulated in LSGs of patients with IgG4-RD, compared with only a few cells in pSS patients and none of the controls. The numbers of CCL18-producing macrophages, CD11c+ cells, and plasmacytes in LSGs were significantly higher in IgG4-RD patients than in pSS patients and control (p < .05, each). Many T and B cells and some plasmacytes expressed CCR8 in LSGs of IgG4-RD and pSS patients. CCL18 specifically enhanced IgG4 production by stimulated PBMCs.Conclusion: CCL18-CCR8 axis was upregulated in LSGs of patients with IgG4-RD, suggesting possible roles of this axis in the pathogenesis of IgG4-RD.Key messagesThe CCL18-CCR8 axis in labial salivary glands (LSGs) and lacrimal glands of IgG4-RD patients was specifically upregulated compared with primary Sjögren's syndrome and control subjects.This axis might be a potentially novel therapeutic target in IgG4-RD, based on its important etiopathogenic roles, such as chemotaxis of various cells, induction of fibrosis, and enhancement of IgG4 production.

Transgenic rice seeds expressing altered peptide ligands against the M3 muscarinic acetylcholine receptor suppress experimental sialadenitis-like Sjögren's syndrome.

Objective: We previously reported that Rag1-/- mice inoculated with splenocytes from M3 muscarinic acetylcholine receptor (M3R) knockout mice immunized with an M3R peptide mixture developed sialadenitis-like Sjögren's syndrome (M3R-induced sialadenitis [MIS]). We also found that intravenous administration of altered peptide ligand (APL) of N-terminal 1 (N1), which is one of the T-cell epitopes of M3R, suppressed MIS. In this study, we aimed to evaluate the suppressive ability and its mechanisms of rice seeds expressing N1-APL7 against MIS.Methods: Rice seeds expressing N1 and N1-APL7 were orally administered to MIS mice for 2 weeks. The changes in saliva flow and sialadenitis (salivary gland inflammation) were analyzed. The M3R-specific T-cell response in the spleen and the expression of regulatory molecules in the cervical lymph nodes and mesenteric lymph nodes were also analyzed.Results: Oral administration of N1-APL7-expressing rice seeds significantly recovered reduction in saliva flow and suppressed sialadenitis when compared with treatment with nontransgenic rice seeds and N1 rice seeds. IFNγ production from M3R-reactive T cells tended to decline in the N1-APL7 rice-treated group as compared with those in the other groups. In the N1-APL7 rice-treated group, the mRNA expression levels of Foxp3 in the cervical-lymph-node CD4+ T cells were higher than those in the other groups.Conclusion: Oral administration of N1-APL7-expressing rice suppressed MIS via suppression of M3R-specific IFNγ and IL-17 production and via enhancement of regulatory molecule expression.Key messagesWe generated N1-peptide- or N1-APL7-expressing rice seeds. Oral administration of N1-APL7-expressing rice seeds significantly recovered the reduction of saliva flow and suppressed sialadenitis via the suppression of M3R specific IFNγ and IL-17 production and via enhancement of regulatory T (Treg) cells.

RORγt antagonist improves Sjögren's syndrome-like sialadenitis through downregulation of CD25.

OBJECTIVE: We reported previously that T-cell-specific RORγt-transgenic mice under human CD2 promoter (RORγt-Tg mice) developed severe spontaneous Sjögren's syndrome (SS)-like sialadenitis, induced by RORγt-overexpressing CD4+ T cells and reduced regulatory T cells. The purpose of this study was to clarify the effectiveness and mechanisms of action of A213, a RORγt antagonist, in RORγt-Tg mice with SS-like sialadenitis. METHODS: Six-week-old RORγt-Tg mice were administered orally of A213 or phosphate-buffered saline every 3 days for 2 weeks. We analyzed saliva volume, histopathology of salivary glands, populations of T cells in splenocytes and cervical lymph nodes (cLNs), and the protein expression levels of CD69 on CD4+ CD25+ Foxp3- and CD4+ CD25+ Foxp3+ cells in cLNs. We also investigated in vitro the potential immunomechanisms of action of A213. RESULTS: A213 significantly increased saliva volume, reduced mononuclear cell infiltration in salivary glands, and reduced the focus score of sialadenitis. Analysis of the immunomechanisms using cLNs showed A213 significantly reduced the proportion of CD4+ CD25+ /CD4+ T cells and the protein expression levels of CD69 on CD4+ CD25+ Foxp3- cells. In vitro experiments showed that A213 suppressed CD25 expression on CD4+ T cells and reduced IL-2 production from CD4+ T cells derived from RORγt-Tg mice. CONCLUSION: A213 improves SS-like sialadenitis through the inhibition of CD4+ CD25+ cells in cLNs.

Activation of the mismatch-specific endonuclease EndoMS/NucS by the replication clamp is required for high fidelity DNA replication.

The mismatch repair (MMR) system, exemplified by the MutS/MutL proteins, is widespread in Bacteria and Eukarya. However, molecular mechanisms how numerous archaea and bacteria lacking the mutS/mutL genes maintain high replication fidelity and genome stability have remained elusive. EndoMS is a recently discovered hyperthermophilic mismatch-specific endonuclease encoded by nucS in Thermococcales. We deleted the nucS from the actinobacterium Corynebacterium glutamicum and demonstrated a drastic increase of spontaneous transition mutations in the nucS deletion strain. The observed spectra of these mutations were consistent with the enzymatic properties of EndoMS in vitro. The robust mismatch-specific endonuclease activity was detected with the purified C. glutamicum EndoMS protein but only in the presence of the ß-clamp (DnaN). Our biochemical and genetic data suggest that the frequently occurring G/T mismatch is efficiently repaired by the bacterial EndoMS-ß-clamp complex formed via a carboxy-terminal sequence motif of EndoMS proteins. Our study thus has great implications for understanding how the activity of the novel MMR system is coordinated with the replisome and provides new mechanistic insight into genetic diversity and mutational patterns in industrially and clinically (e.g. Mycobacteria) important archaeal and bacterial phyla previously thought to be devoid of the MMR system.