Abatacept downregulates Fcγ receptor I on circulating monocytes: a potential therapeutic mechanism in patients with rheumatoid arthritis

Background

Abatacept is a recombinant fusion protein composed of the extracellular domain of cytotoxic T-lymphocyte antigen 4 and the Fc portion of immunoglobulin (Ig) G. The mechanism of action of abatacept in rheumatoid arthritis (RA) is believed to be competitive inhibition of T cell costimulation mediated by the binding of CD28 to CD80/CD86 on antigen-presenting cells, and recent studies have shown that abatacept induces reverse signaling in macrophages and osteoclast precursors in a T cell-independent manner. This study aimed to investigate the therapeutic effects of abatacept on circulating monocytes that contribute to RA pathogenesis.

Methods

Purified circulating monocytes derived from RA patients and controls were cultured in the absence or presence of abatacept or CD28-Ig for 24 h. The recovered cells were subjected to flow cytometry to evaluate the expression levels of cell surface molecules, and cytokines and chemokines in the culture supernatant were measured by multiplex bead arrays. The expression of candidate molecules was further examined by immunoblotting using total cellular extracts of the cultured monocytes. Finally, the effects of abatacept on cytokine production in monocytes stimulated with the immune complex of anti-citrullinated peptide antibodies (ACPAs) were examined.

Results

CD64/FcγRI was identified as a monocyte-derived molecule that was downregulated by abatacept but not CD28-Ig. This effect was observed in both RA patients and controls. The abatacept-induced downregulation of CD64/FcγRI was abolished by treatment with anti-CD86 antibodies but not anti-CD80 antibodies. Abatacept suppressed the production of interleukin (IL)-1β, IL-6, C-C motif chemokine ligand 2, and tumor necrosis factor-α in cultured monocytes stimulated with the ACPA immune complex.

Conclusions

The therapeutic effects of abatacept on RA are mediated, in part, by the downregulation of CD64/FcγRI on circulating monocytes via direct binding to CD86 and the suppression of immune complex-mediated inflammatory cytokine production.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-022-02886-8.

Serum rheumatoid factor IgA, anti-citrullinated peptide antibodies with secretory components, and anti-carbamylated protein antibodies associate with interstitial lung disease in rheumatoid arthritis

Objective

Rheumatoid arthritis (RA) is often complicated with chronic lung diseases (CLD), including interstitial lung disease (ILD) and airway disease, which occur as extra-articular manifestations. CLD in RA have been associated with the production of rheumatoid factor (RF), anti-citrullinated peptide antibody (ACPA), or anti-carbamylated protein (CarP) antibody. However, few validation studies have been performed thus far. In the present study, we investigated the association of RF, ACPA, and anti-CarP antibodies with RA complicated with CLD.

Methods

Sera from RA patients with or without CLD were collected. The levels of serum RF, RF immunoglobulin A (IgA), ACPA IgG, ACPA IgA, and ACPA secretory component (SC) were measured using enzyme-linked immunosorbent assay.

Results

The comparison of RA patients with and without CLD showed that RF IgA was associated with ILD (mean ± standard deviation: 206.6 ± 400.5 vs. 95.0 ± 523.1 U/ml, respectively, P = 1.13 × 10^− 8), particularly usual interstitial pneumonia (UIP) (263.5 ± 502.0 U/ml, P = 1.00 × 10^− 7). ACPA SC was associated with RA complicated with ILD (mean ± standard deviation: 8.6 ± 25.1 vs. 2.3 ± 3.4 U/ml, respectively, P = 0.0003), particularly nonspecific interstitial pneumonia (NSIP) (10.7 ± 31.5 U/ml, P = 0.0017). Anti-CarP antibodies were associated with RA complicated with ILD (0.042 ± 0.285 vs. 0.003 ± 0.011 U/ml, respectively, P = 1.04X10^− 11).

Conclusion

RF IgA and ACPA SC in RA were associated with UIP and NSIP, respectively, suggesting different specificities in patients with RA. Anti-CarP antibodies were associated with ILD in RA. These results may help elucidate the different pathogeneses of UIP and NSIP in RA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04985-0.

A review of liquid biopsy as a tool to assess epigenetic, cfDNA and miRNA variability as methotrexate response predictors in patients with rheumatoid arthritis

Rheumatoid arthritis (RA) is a common autoimmune inflammatory disease affecting 0.5-1% of adults worldwide. Achieving long term remission or low disease activity is possible through early diagnosis, rapid initiation of disease modifying anti-rheumatic drugs (DMARDs) and implementation of a treat to target approach. Initial DMARD therapy usually involves methotrexate (MTX), either alone or in combination with other agents, however 40% of RA patients do not respond adequately, putting them at risk of disease progression and unnecessary exposure to MTX related adverse effects. Early predictors of MTX response would therefore enable a more personalized treatment strategy, ensuring timely access to MTX for those likely to respond and importantly, early initiation of alternative treatment for those in which MTX is unlikely to be efficacious. Predicting response to treatment will most likely require consideration of the clinical characteristics of the patient and interrogation of a number of factors including genetic, epigenetic, cell free DNA (cfDNA) and microRNA (miRNA), all of which can be investigated through blood derived liquid biopsies. This review will summarize the existing literature examining the use of epigenetic factors, cfDNA and miRNA as response predictors among RA patients treated with MTX.

Differential regulation and correlation between galectin-9 and anti-CCP antibody (ACPA) in rheumatoid arthritis patients

Background

Galectin-9 (Gal-9) is involved in the regulatory process of immune responses or inflammation. The aim of the present study is to characterize circulating Gal-9 in patients with rheumatoid arthritis (RA) and its relationship with RA disease activity and phenotype.

Methods

A total of 116 RA patients and 31 age-matched healthy controls were included in this study. Disease activity of RA patients was determined by Disease Activity Score of 28 joint scoring system (DAS28-ESR). Levels of Gal-9 in serum were determined by enzyme-linked immunosorbent assay (ELISA).

Results

Serum levels of Gal-9 were significantly higher in patients with RA compared to those in controls (median 7577 pg/ml [interquartile range (IQR) 5570–10,201] versus 4738 pg/ml [IQR 4267–5630], p = 0.001). There were significant differences in serum Gal-9 between RA patients with and without RA-ILD (9606 pg/ml [IQR 8522–12,167] versus 7078 pg/ml [IQR 5225–9447], p < 0.001) or those with and without advanced joint damage (stage II–IV, 9606 pg/ml [IQR 8522–12,167] versus 7078 pg/ml [IQR 5225–9447], p < 0.001). Although serum levels of Gal-9 correlated with the titers of ACPA (r = 0.275, p = 0.002), levels of ACPA titers conferred the different relationship, between serum Gal-9 and inflammatory mediators or RA disease activity. Although Gal-9 was correlated with ACPA titers (r = 0.508, p = 0.002), there was no correlation between Gal-9 levels and erythrocyte sedimentation rate (ESR), matrix metalloproteinase-3 (MMP-3), or DAS28-ESR in RA patients with high titers of ACPA (> 200 U/ml). Conversely, Gal-9 was correlated with MMP-3 (r = 0.300, p = 0.007) or DAS28-ESR (r = 0.331, p = 0.004) but not with ACPA titer in RA patients with low titers of ACPA titers (< 200 U/ml).

Conclusions

Serum levels of Gal-9 were increased in RA patients and associated with RA disease activity in RA patients without high titers of ACPA. The levels of ACPA titers may influence the values of circulating Gal-9 in RA patients with various clinical phenotypes. These data suggest that Gal-9 possessed the properties of pro-inflammatory or arthropathic biomarker under the status of ACPA titers.

Autoantibodies and their Judicious Use in Pediatric Rheumatology Practice

Autoantibody testing forms an important part of diagnostic workup of patients in Pediatric rheumatology practice. However it is important to understand that the mere presence of autoantibodies does not necessarily mean the presence of an underlying autoimmune disease. Autoantibodies may be present decades before the development of clinical manifestations of an autoimmune disease and may be viewed as harbingers of Autoimmune disease. On the other hand, low-affinity autoantibodies may be present in normal healthy individuals; these natural autoantibodies serve an important function in immune regulation and tolerance. Autoantibody testing in pediatric practice mainly includes testing for anti-nuclear antibodies, anti-dsDNA antibodies, anti-neutrophil cytoplasmic autoantibodies and antiphospholipid antibodies. Rheumatoid factor and anti-CCP do not have much significance in the diagnostic schema in pediatric rheumatology, except perhaps for classification of juvenile idiopathic arthritis (JIA) and prognostication in late-onset polyarticular JIA. The positive predictive value (PPV) of any laboratory test depends on the prevalence of the disease in the population being tested. Hence, test ordering practices greatly impact the performance characteristics and positive predictive value of any laboratory test. A restricted test ordering only in patients with clinical signs and symptoms suggestive of autoimmune disease would thus greatly increase the PPV of tests such as antinuclear antibody used for diagnosing autoimmunity.