Anti-centromere antibodies target centromere-kinetochore macrocomplex: a comprehensive autoantigen profiling.

OBJECTIVES: Anti-centromere antibodies (ACAs) are detected in patients with various autoimmune diseases such as Sjögren's syndrome (SS), systemic sclerosis (SSc) and primary biliary cholangitis (PBC). However, the targeted antigens of ACAs are not fully elucidated despite the accumulating understanding of the molecular structure of the centromere. The aim of this study was to comprehensively reveal the autoantigenicity of centromere proteins. METHODS: A centromere antigen library including 16 principal subcomplexes composed of 41 centromere proteins was constructed. Centromere protein/complex binding beads were used to detect serum ACAs in patients with SS, SSc and PBC. ACA-secreting cells in salivary glands obtained from patients with SS were detected with green fluorescent protein-fusion centromere antigens and semiquantified with confocal microscopy. RESULTS: A total of 241 individuals with SS, SSc or PBC and healthy controls were recruited for serum ACA profiling. A broad spectrum of serum autoantibodies was observed, and some of them had comparative frequency as anti-CENP-B antibody, which is the known major ACA. The prevalence of each antibody was shared across the three diseases. Immunostaining of SS salivary glands showed the accumulation of antibody-secreting cells (ASCs) specific for kinetochore, which is a part of the centromere, whereas little reactivity against CENP-B was seen. CONCLUSIONS: We demonstrated that serum autoantibodies target the centromere-kinetochore macrocomplex in patients with SS, SSc and PBC. The specificity of ASCs in SS salivary glands suggests kinetochore complex-driven autoantibody selection, providing insight into the underlying mechanism of ACA acquisition.

Antigen-driven selection of antibodies against SSA, SSB and the centromere 'complex', including a novel antigen, MIS12 complex, in human salivary glands.

OBJECTIVES: Recent evidences have revealed that anti-SSA/SSB antibodies, the major autoantibodies in Sjögren's syndrome (SS), are produced in salivary glands. This study aims to clarify overall of autoantibody production at lesion site, including anti-centromere antibody (ACA)-positive SS. METHODS: Antibodies of antibody-secreting cells in human salivary glands were produced as recombinant antibodies. The reactivity of these antibodies and their revertants were investigated by ELISA and newly developed antigen-binding beads assay, which can detect conformational epitopes. The target of uncharacterised antibodies was identified by immunoprecipitation and mass spectrometry. Autoantibody-secreting cells in salivary gland tissue were identified by immunohistochemistry using green fluorescent protein-autoantigen fusion proteins. RESULTS: A total of 256 lesion antibodies were generated, and 69 autoantibodies including 24 ACAs were identified among them. Beads assay could detect more autoantibodies than ELISA, suggesting autoantibodies target to antigens with native conformation. After somatic hypermutations were reverted, autoantibodies drastically decreased antigen reactivity. We showed that MIS12 complex, a novel target of ACA, and CENP-C are major targets of ACA produced in salivary glands by examining cloned antibodies and immunohistochemistry, whereas few anti-CENP-B antibodies were detected. The target profiling of serum ACA from 269 patients with SS, systemic sclerosis (SSc), primary biliary cirrhosis (PBC) and healthy controls revealed that ACA-positive patients have antibodies against various sites of centromere complex regardless of disease. CONCLUSION: We showed direct evidences of antigen-driven maturation of anti-SSA/SSB antibody and ACA in SS lesion. ACA recognises centromere 'complex' rather than individual protein, and this feature is common among patients with SS, SSc and PBC.

Loss of Sprouty4 in T cells ameliorates experimental autoimmune encephalomyelitis in mice by negatively regulating IL-1ß receptor expression.

Th17 cells, which have been implicated in autoimmune diseases, require IL-6 and TGF-ß for early differentiation. To gain pathogenicity, however, Th17 cells require IL-1ß and IL-23. The underlying mechanism by which these confer pathogenicity is not well understood. Here we show that Sprouty4, an inhibitor of the PLCγ-ERK pathway, critically regulates inflammatory Th17 (iTh17) cell differentiation. Sprouty4-deficient mice, as well as mice adoptively transferred with Sprouty4-deficient T cells, were resistant to experimental autoimmune encephalitis (EAE) and showed decreased Th17 cell generation in vivo. In vitro, Sprouty4 deficiency did not severely affect TGF-ß/IL-6-induced Th17 cell generation but strongly impaired Th17 differentiation induced by IL-1/IL-6/IL-23. Analysis of Th17-related gene expression revealed that Sprouty4-deficient Th17 cells expressed lower levels of IL-1R1 and IL-23R, while RORγt levels were similar. Consistently, overexpression of Sprouty4 or pharmacological inhibition of ERK upregulated IL-1R1 expression in primary T cells. Thus, Sprouty4 and ERK play a critical role in developing iTh17 cells in Th17 cell-driven autoimmune diseases.

Anti-human-TIGIT agonistic antibody ameliorates autoimmune diseases by inhibiting Tfh and Tph cells and enhancing Treg cells.

T cells play important roles in autoimmune diseases, but it remains unclear how to optimally manipulate them. We focused on the T cell immunoreceptor with Ig and ITIM domains (TIGIT), a coinhibitory molecule that regulates and is expressed in T cells. In autoimmune diseases, the association between TIGIT-expressing cells and pathogenesis and the function of human-TIGIT (hu-TIGIT) signalling modification have not been fully elucidated. Here we generated anti-hu-TIGIT agonistic monoclonal antibodies (mAbs) and generated hu-TIGIT knock-in mice to accurately evaluate the efficacy of mAb function. Our mAb suppressed the activation of CD4+ T cells, especially follicular helper T and peripheral helper T cells that highly expressed TIGIT, and enhanced the suppressive function of naïve regulatory T cells. These results indicate that our mAb has advantages in restoring the imbalance of T cells that are activated in autoimmune diseases and suggest potential clinical applications for anti-hu-TIGIT agonistic mAbs as therapeutic agents.

JAK2 V617F-dependent upregulation of PU.1 expression in the peripheral blood of myeloproliferative neoplasm patients.

Myeloproliferative neoplasms (MPN) are multiple disease entities characterized by clonal expansion of one or more of the myeloid lineages (i.e. granulocytic, erythroid, megakaryocytic and mast cell). JAK2 mutations, such as the common V617F substitution and the less common exon 12 mutations, are frequently detected in such tumor cells and have been incorporated into the diagnostic criteria published by the World Health Organization since 2008. However, the mechanism by which these mutations contribute to MPN development is poorly understood. We examined gene expression profiles of MPN patients focusing on genes in the JAK-STAT signaling pathway using low-density real-time PCR arrays. We identified the following 2 upregulated genes in MPN patients: a known target of the JAK-STAT axis, SOCS3, and a potentially novel target, SPI1, encoding PU.1. Induction of PU.1 expression by JAK2 V617F in JAK2-wildtype K562 cells and its downregulation by JAK2 siRNA transfection in JAK2 V617F-positive HEL cells supported this possibility. We also found that the ABL1 kinase inhibitor imatinib was very effective in suppressing PU.1 expression in BCR-ABL1-positive K562 cells but not in HEL cells. This suggests that PU.1 expression is regulated by both JAK2 and ABL1. The contribution of the two kinases in driving PU.1 expression was dominant for JAK2 and ABL1 in HEL and K562 cells, respectively. Therefore, PU.1 may be a common transcription factor upregulated in MPN. PU.1 is a transcription factor required for myeloid differentiation and is implicated in erythroid leukemia. Therefore, expression of PU.1 downstream of activated JAK2 may explain why JAK2 mutations are frequently observed in MPN patients.

A novel PAX3 rearrangement in embryonal rhabdomyosarcoma.

Rhabdomyosarcoma is the most common soft tissue tumor seen in children and young adults, and it can be classified into 2 major histological subtypes, alveolar and embryonal. In the alveolar subtype, 2 recurrent chromosomal translocations, t(2;13)(q35;q14) and its variant t(1;13)(p36;q14), have been identified as the specific cytogenetic abnormalities. These translocations produce the PAX3-FOXO1 and PAX7-FOXO1 fusion genes, respectively. In the embryonal subtype, however, no recurrent chromosomal abnormalities have been identified. In this study, we analyzed the complex chromosomal translocation in one case with embryonal rhabdomyosarcoma by means of spectral karyotyping (SKY) and identified a novel translocation involving chromosome band 2q35, which is the locus of PAX3 gene. Furthermore, we identified the novel PAX3 rearrangement using fluorescence in situ hybridization (FISH) analysis. Additional identification of the partner gene may help disclose the molecular mechanism of the development of this embryonal subtype.