Anti-aminoacyl tRNA synthetase antibodies showing the discrepancy between enzyme-linked immunosorbent assay and RNA-immunoprecipitation.

Anti-aminoacyl-tRNA synthetase (ARS) antibodies are myositis-specific antibodies associated with anti-synthetase syndrome (ASSD). Some patients are positive for anti-ARS antibodies on enzyme-linked immunosorbent assay (ELISA) but negative on RNA-immunoprecipitation (RNA-IP) (the gold standard method). Whether these patients should be considered truly positive for anti-ARS antibodies remains unclear. Therefore, we investigated the clinical characteristics of these patients and verified the authenticity of their anti-ARS positivity. Patients who were positive for anti-ARS antibodies on ELISA were divided into the non-discrepant (positive on RNA-IP, n = 52) and discrepant (negative on RNA-IP, n = 8) groups. Patient clinical characteristics were compared between the groups. For each positive individual, the authenticity of anti-ARS antibody positivity on ELISA was cross-examined using protein-IP and western blotting. All patients in the discrepant group had lung involvement, including five (63%) with interstitial lung disease. The overall survival time was significantly lower in the discrepant group than in the non-discrepant group (p < 0.05). Validation tests confirmed the presence of anti-ARS antibodies in the sera of the discrepant group but indicated different reactivity from typical anti-ARS antibodies. In conclusion, some anti-ARS antibodies are detected by ELISA but not RNA-IP. Such anti-ARS antibody discrepancies need further elucidation to attain validation of the diagnostic process in ASSD.

Frequency, proportion of PF-ILD, and prognostic factors in patients with acute exacerbation of ILD related to systemic autoimmune diseases.

BACKGROUND: Acute exacerbation (AE) of systemic autoimmune disease-related interstitial lung diseases (SAID-ILD) is less common than AE of idiopathic pulmonary fibrosis (IPF) and the details of AE-SAID-ILD have not been elucidated, but the prognosis is similarly devastating. This study was undertaken to determine the incidences of AE-ILD in each SAID and to elucidate the proportion of progressive fibrosing (PF)-ILD in AE-SAID-ILD. METHODS: We retrospectively analysed data for patients with SAID-ILD who were diagnosed and observed at our hospital between 1999 and 2020. RESULTS: Two hundred and thirty-two patients with SAID-ILD were enrolled, with a mean observation period of 100.2 months. AE-SAID-ILD was found in 25 patients (10.78%), mainly in patients with RA (17 patients, 68%) and elderly male patients with a smoking history. The overall incidence of AE-SAID-ILD was 1.29%/person-year, and the incidence for each SAID was as follows: RA 2.193, microscopic polyarteritis (MPA) 3.203, systemic sclerosis (SSc) 2.277, primary Sjögren syndrome 0.426, and polymyositis/dermatomyositis 0.222. The incidence of AE of RA/MPA/SSc-ILD was significantly higher than that of other AE-SAID-ILD (p < 0.001). Five of 25 patients (20%) fulfilled the criteria for PF-ILD. The 90-day survival rate was 48.0%, and a higher neutrophil count at AE (HR 13.27, 95%CI 2.447-246, p = 0.001) and early commencement of long-duration direct haemoperfusion with a polymyxin B-immobilised fibre column (HR 0.105, 95%CI 0.005-0.858, p = 0.035) were significant prognostic factors. CONCLUSIONS: The incidence of AE-SAID-ILD was significantly higher in patients with RA, MPA, or SSc than in patients with other SAID. Furthermore, even in patients with AE-SAID-ILD, the proportion of PF-ILD just before AE was not high (20%).

Anti-ribosomal P protein antibodies in patients with systemic lupus erythematosus is associated with hyperferritinemia.

AIM: Anti-ribosomal P protein antibodies (anti-ribo P) have been reported as one of the specific autoantibodies in patients with systemic lupus erythematosus (SLE) and has been demonstrated to bind and activate macrophages in vitro. Clinically, hyperferritinemia has been known to be a biomarker for macrophage activation. The aim of this study is to clarify the relationship of anti-ribo P and clinical characteristics and biomarkers including serum ferritin in patients with SLE. METHODS: Clinical parameters and laboratory data were measured in patients with active SLE (N = 127) in our university hospital. The risk factors affected by anti-ribo P were retrospectively calculated by logistic regression analysis, and the correlation of anti-ribo P and clinical factors was demonstrated. RESULTS: Anti-ribo P was significantly elevated in active SLE compared to non-SLE diseases (P < .0001). Sensitivity and the specificity of anti-ribo P in patients with SLE were 32.0% and 99.3%, respectively. Patients positive for anti-ribo P had the highest risk for elevated serum ferritin (odds ratio: 8.432). Accordingly, anti-ribo P positive patients had significantly elevated serum ferritin compared to negative patients (P = .024). A significant positive correlation was observed between the anti-ribo P titer and the serum ferritin level (r2  = .07, t = 5.22, P = .0081), but not serum interleukin (IL)-6 in SLE patients. CONCLUSION: The presence of anti-ribo P is a risk factor for higher ferritin levels that is independent of systemic inflammation regulated by IL-6. We speculate that anti-ribo P could be directly associated with macrophage activation leading to hyperferritinemia in patients with SLE.

Clinical Significance of Cold-Inducible RNA-Binding Protein in Idiopathic Pulmonary Fibrosis.

BACKGROUND: Idiopathic pulmonary fibrosis (IPF) is associated with a poor prognosis with variable clinical course. Early identification of patients at high risk for disease progression and death would lead to early therapeutic intervention and thereby improvement of outcomes. Cold-inducible RNA-binding protein (CIRBP) is produced in response to cellular stresses, which is implicated in multiple biological processes, including cell survival and proliferation. RESEARCH QUESTION: Is CIRBP a useful biomarker for predicting the outcomes of patients with IPF? STUDY DESIGN AND METHODS: This study included 95 and 93 patients with IPF from two independent hospitals (derivation and validation cohorts, respectively). The associations of serum CIRBP level on IPF diagnosis with disease progression within 1 year after diagnosis (ie, ≥10% relative decline in percent predicted FVC or death) and all-cause mortality were retrospectively analyzed. Discrimination performances for predicting these outcomes were evaluated using the c-index. RESULTS: Serum and lung tissue CIRBP levels were higher in patients with IPF than in control subjects. In the derivation cohort, the CIRBPhigh subgroup had significantly higher 1-year disease progression rates and lower cumulative survival rates than the CIRBPlow subgroup, and the results were replicated in the validation cohort. In multivariate analyses, high serum CIRBP level was independently associated with higher 1-year disease progression and all-cause mortality rates in both cohorts. Combining the Gender-Age-Physiology (GAP) and serum CIRBP models improved the c-indexes for predicting 1-year disease progression and all-cause mortality compared with that of each model alone. The c-indexes of serum CIRBP were particularly high in patients with GAP stage I. INTERPRETATION: This study successfully validated that serum CIRBP level was an independent predictor of 1-year disease progression and all-cause mortality in IPF. CIRBP is a promising biomarker that can help identify high-risk patients with IPF, especially in the early stage.

Serum S100A8 and S100A9 as prognostic biomarkers in acute exacerbation of idiopathic pulmonary fibrosis.

BACKGROUND: Acute exacerbation of idiopathic pulmonary fibrosis (AE-IPF) is a devastating and life-threatening condition during its clinical course. Biomarkers for precisely anticipating the prognosis of AE-IPF remain to be fully established. The objective of this study was to clarify whether S100A8 and S100A9, which are calcium-binding proteins mainly produced by activated neutrophils, are significant prognostic biomarkers in AE-IPF. METHODS: Thirty-seven patients with AE-IPF who were diagnosed and treated at our hospital were retrospectively evaluated. The serum levels of S100A8 and S100A9 were measured using enzyme-linked immunosorbent assay, and the relationships between these levels and clinical parameters or prognosis were evaluated. RESULTS: The serum levels of S100A8 (median 386.5 ng/mL) and S100A9 (median 60.2 ng/mL) in patients with AE-IPF were significantly higher than those in age-matched healthy controls and in patients at IPF diagnosis (p < 0.001 for all combinations). The serum levels of S100A8 negatively correlated with percent forced vital capacity (r = -0.356, p = 0.049) and positively correlated with peripheral white blood cell number (r = 0.509, p = 0.002). Immunohistochemical staining of autopsy lung specimens showed that neutrophils, present mainly in the alveolar septum, were positive for S100A8 and S100A9. Patients with AE-IPF with higher levels of S100A8 or S100A9 showed significantly worse 3-month survival than those with lower levels (log-rank test, both p = 0.028). Finally, in multivariate analysis, the serum levels of both S100A8 and S100A9 were significant prognostic factors (hazard ratio 4.032, p = 0.023 and hazard ratio 4.327, p = 0.012). CONCLUSION: The serum levels of S100A8 and S100A9 at AE were significant prognostic biomarkers in patients with AE-IPF.

Clinical significance of serum S100 calcium-binding protein A4 in idiopathic pulmonary fibrosis.

BACKGROUND AND OBJECTIVE: Idiopathic pulmonary fibrosis (IPF) is a progressive interstitial lung disease with a poor prognosis. There are no established serum biomarkers for predicting the outcomes of IPF. S100 calcium-binding protein A4 (S100A4) is considered as a marker of fibroblasts; however, its clinical application remains to be investigated. We evaluated the clinical relevance of S100A4 in IPF patients. METHODS: Serum S100A4 levels in 95 consecutive IPF patients and 50 healthy controls (HC) were measured using enzyme-linked immunosorbent assay. S100A4 expression in lung tissues was determined using immunohistochemistry/immunofluorescence and its association with disease progression (defined as deterioration in lung function or death) and mortality was assessed using Kaplan-Meier method and Cox hazards analysis. RESULTS: Serum S100A4 levels were undetectable in all HC but were detectable in 26 (27.3%) of the 95 IPF patients (P < 0.01). Immunostaining of lung tissues from IPF patients showed aggregation of numerous S100A4-expressing cells around the fibroblastic foci and mature fibrotic regions. IPF patients with higher serum S100A4 levels had a significantly worse prognosis than those with low serum levels (2-year cumulative survival rate: 41.7% vs 77.0%, respectively, P < 0.01). On multivariate analyses, baseline serum S100A4 levels (per 10 ng/mL increase) were independently associated with higher disease progression rate (odds ratio: 1.06, P = 0.01) and higher mortality (hazard ratio: 1.18, P = 0.03). CONCLUSION: S100A4 is a promising serum biomarker that may help predict disease progression/mortality. Our findings may help establish treatment strategies for IPF.