Baseline serum levels of IgA anti-cyclic citrullinated protein antibodies in early rheumatoid arthritis predict radiographic progression after 11 years of treatment: a secondary analysis of the CIMESTRA study

OBJECTIVE

Smoking and periodontitis are risk factors for developing rheumatoid arthritis (RA), suggesting a break of tolerance on mucosal surfaces. Immunoglobulin A (IgA) antibodies are part of the mucosal immune system. The dominant autoantibodies in RA are anti-cyclic citrullinated protein antibodies (ACPAs), and IgG and IgA subclasses exist simultaneously. This study aimed to investigate the association of ACPA IgA subtypes with disease activity and long-term radiographic outcomes in RA, compared with ACPA IgG.

METHOD

Total ACPA IgG, IgA, IgA1, and IgA2 were quantified in serum from patients with early RA (n = 97). Patient characteristics, IgM rheumatoid factor (IgM-RF) status, clinical and biochemical disease activity scores, and radiographic status evaluated by total Sharp score (TSS), were assessed at baseline and after 2 and 11 years of treatment.

RESULTS

All patients with ACPA IgA also had ACPA IgG. ACPA IgA positivity was associated with IgM-RF and male gender. Both ACPA IgA and IgG levels at baseline were weakly associated with disease activity markers. Baseline ACPA IgA and IgG did not show a linear correlation with radiographic status after 10 years, but could predict radiographic progression (ΔTSS ≥ 5 from 0 to 11 years), with positive likelihood ratios of 3.7 and 4.0, respectively.

CONCLUSION

ACPA IgA and IgG were weakly associated with disease activity in early RA. RA patients with a ΔTSS ≥ 5 after 11 years of treatment had higher ACPA IgG and ACPA IgA levels at baseline; however, none of the ACPA subtypes was superior in predicting long-term radiographic progression.

Clonally expanded CD38hi cytotoxic CD8 T cells define the T cell infiltrate in checkpoint inhibitor-associated arthritis

Immune checkpoint inhibitor (ICI) therapies used to treat cancer, such as anti-PD-1 antibodies, can induce autoimmune conditions in some individuals. The T cell mechanisms mediating such iatrogenic autoimmunity and their overlap with spontaneous autoimmune diseases remain unclear. Here, we compared T cells from the joints of 20 patients with an inflammatory arthritis induced by ICI therapy (ICI-arthritis) with two archetypal autoimmune arthritides, rheumatoid arthritis (RA) and psoriatic arthritis (PsA). Single-cell transcriptomic and antigen receptor repertoire analyses highlighted clonal expansion of an activated effector CD8 T cell population in the joints and blood of patients with ICI-arthritis. These cells were identified as CD38hiCD127- CD8 T cells and were uniquely enriched in ICI-arthritis joints compared with RA and PsA and also displayed an elevated interferon signature. In vitro, type I interferon induced CD8 T cells to acquire the ICI-associated CD38hi phenotype and enhanced cytotoxic function. In a cohort of patients with advanced melanoma, ICI therapy markedly expanded circulating CD38hiCD127- T cells, which were frequently bound by the therapeutic anti-PD-1 drug. In patients with ICI-arthritis, drug-bound CD8 T cells in circulation showed marked clonal overlap with drug-bound CD8 T cells from synovial fluid. These results suggest that ICI therapy directly targets CD8 T cells in patients who develop ICI-arthritis and induces an autoimmune pathology that is distinct from prototypical spontaneous autoimmune arthritides.

Co-Inhibitory Molecules – Their Role in Health and Autoimmunity; Highlighted by Immune Related Adverse Events

Immune checkpoint receptors are key players in regulating the immune response. They are responsible for both generating an immune response sufficient to kill invading pathogens, balancing the same response, and protecting against tissue destruction or the development of autoimmune events. The central role of the co-inhibitory receptors also referred to as inhibitory immune checkpoints, including PD-1 and CTLA-4 has become especially evident with the cancer treatments targeting these receptors. Blocking these pathways enhances the immune activity, resulting in both an increased chance of cancer clearance, at the same time induction of immune-related adverse events (irAE). Some of these irAE progress into actual autoimmune diseases with autoantibodies and symptoms, undistinguished from the naturally occurring diseases. This review will take advantage of the lessons learned from immune checkpoint blockade and relate this knowledge to our understanding of the same pathways in naturally occurring autoimmune diseases, mainly focusing on rheumatic diseases.

The Programmed Death-1 Pathway Counter-Regulates Inflammation-Induced Osteoclast Activity in Clinical and Experimental Settings

Objective

The programmed death-1 (PD-1) pathway is essential for maintaining self-tolerance and plays an important role in autoimmunity, including rheumatoid arthritis (RA). Here, we investigated how membrane-bound and soluble (s)PD-1 influence bone homeostasis during chronic inflammation, exemplified in RA.

Methods

Bone mineral density and bone microstructure were examined in PD-1 and PD-L1 knockout (KO) mice and compared with wild-type (WT) mice. Receptor activator of nuclear factor kappa-B ligand (RANKL) was measured in serum, and the expression examined on activated bone marrow cells. Osteoclast formation was examined in cells from murine spleen and bone marrow and from human synovial fluid cells. sPD-1 was measured in chronic and early (e)RA patients and correlated to markers of disease activity and radiographic scores.

Results

PD-1 and PD-L1 KO mice showed signs of osteoporosis. This was supported by a significantly reduced trabecular bone volume fraction and deteriorated microstructure, as well as increased osteoclast formation and an increased RANKL/OPG ratio. The recombinant form of sPD-1 decreased osteoclast formation in vitro, but was closely associated with disease activity markers in eRA patients. Sustained elevated sPD-1 levels indicated ongoing inflammation and were associated with increased radiographic progression.

Conclusion

The PD-1 pathway is closely associated with bone homeostasis, and lacking members of this pathway causes a deteriorated bone structure. The immunological balance in the microenvironment determines how the PD-1 pathway regulates osteoclast formation. In eRA patients, sPD-1 may serve as a biomarker, reflecting residual but clinically silent disease activity and radiographic progression.

CXCL13 predicts long term radiographic status in early rheumatoid arthritis

OBJECTIVES

It remains challenging to identify rheumatoid arthritis (RA) patients at a high risk of joint destruction. The C-X-C motif chemokine 13 (CXCL13) has previously been suggested as a marker of disease activity in RA. Here, we investigate the potential of plasma CXCL13 as a marker of long-term radiographic status and progression.

METHODS

CXCL13 was measured in plasma from treatment naïve RA patients (n = 158) with 11-year follow-up. At baseline, clinical and biochemical disease activity scores were obtained; among these C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), disease activity score in 28 joints with CRP(DAS28CRP), number of, swollen joints (SJC28) and radiographic status, evaluated by total Sharp score (TSS). Age and gender matched healthy controls (HC) were included.

RESULTS

CXCL13 was significantly increased at baseline and decreased during treatment, however without reaching the level in HC. At baseline, CXCL13 was associated with both CRP and ESR, but not with other markers of disese activity. Baseline CXCL13 correlated with both TSS and radiographic progression (ΔTSS) at 11 years. With a 89% probability, levels of CXCL13 above 85 pg/ml predicted the risk of a TSS of 5 or above, after 11 years of treatment. Comparing with CRP, DAS28CRP, SJC28 and anti-citrullinated peptide antibody status, CXCL13 was superior in predicting 11-year joint destruction.

CONCLUSION

In early RA, one single measurement of plasma CXCL13 at baseline, is superior to currently used clinical and serological disease markers, to predict longterm radiographic status and progression.

Programmed death ligand 2 - A link between inflammation and bone loss in rheumatoid arthritis

Objective

Active rheumatoid arthritis (RA) is accompanied by increased appendicular and axial bone loss, closely associated to the degree of inflammation. The programmed death-1 (PD-1) pathway is important for maintaining peripheral tolerance, and its ligand PD-L2 has recently been associated with bone morphogenetic protein activity. Here, we report that PD-L2 plays a central role in RA osteoimmunology.

Methods

Femoral bone mineral density (BMD) and trabecular bone microstructure were evaluated by micro-CT in wild type (WT) and PD-L2^−/− mice. Osteoclasts were generated from RA synovial fluid mononuclear cells and peripheral blood monocytes. The effects of recombinant PD-L2, was evaluated by tartrate-resistant acid phosphatase (TRAP) activity and the development of bone erosions in the presence of anti-citrullinated protein antibodies (ACPA). Plasma soluble (s)PD-L2 levels were measured in patients with early (e)RA (n ​= ​103) treated with methotrexate alone or in combination with the TNF inhibitor Adalimumab.

Results

PD-L2^−/− mice had a decreased BMD and deteriorated trabecular bone microstructure that was not related to the RANKL/OPG pathway. PD-L2 decreased TRAP activity in osteoclasts and decreased ACPA-induced erosions. In the RA synovial membrane PD-L2 was highly expressed especially in the lining layer and plasma sPD-L2 levels were increased in eRA patients and decreased with treatment. One-year sPD-L2 correlated inversely with erosive progression two years after treatment initiation with methotrexate and placebo.

Conclusion

PD-L2 regulates bone homeostasis in RA. Our findings provide new insight into the relationship between the immune system and bone homeostasis, and suggest a potential therapeutic target for limiting inflammatory bone loss in RA.

•

PD-L2 is closely related to bone homeostasis in a mouse model.

•

PD-L2 inhibits osteoclastogenesis and osteoclast activation in vitro.

•

PD-L2 is highly expressed by cells in the synovial membrane of rheumatoid arthritis.

•

PD-L2 is associated with less radiographic progression in patients with early rheumatoid arthritis.

Extracellular Vesicles Transfer the Receptor Programmed Death-1 in Rheumatoid Arthritis

Introduction

Extracellular vesicles (EVs) have been recognized as route of communication in the microenvironment. They transfer proteins and microRNAs (miRNAs) between cells, and possess immunoregulatory properties. However, their role in immune-mediated diseases remains to be elucidated. We hypothesized a role for EVs in the rheumatoid arthritis (RA) joint, potentially involving the development of T cell exhaustion and transfer of the co-inhibitory receptor programmed death 1 (PD-1).

Methods

Synovial fluid mononuclear cells (SFMCs) and peripheral blood mononuclear cells (PBMCs) from RA patients were investigated for PD-1 and other markers of T cell inhibition. EVs were isolated from RA plasma and synovial fluid. In addition, healthy control (HC) and RA PBMCs and SFMCs were cultured to produce EVs. These were isolated and investigated by immunogold electron microscopy (EM) and also co-cultured with lymphocytes and PD-1 negative cells to investigate their functions. Finally, the miRNA expression profiles were assessed in EVs isolated from RA and HC cell cultures.

Results

Cells from the RA joint expressed several T cell co-inhibitory receptors, including PD-1, TIM-3, and Tigit. ELISA demonstrated the presence of PD-1 in EVs from RA plasma and synovial fluid. Immunogold EM visualized PD-1 expression by EVs. Co-culturing lymphocytes and the PD-1 negative cell line, U937 with EVs resulted in an induction of PD-1 on these cells. Moreover, EVs from RA PBMCs increased proliferation in lymphocytes when co-cultured with these. All EVs contained miRNAs associated with PD-1 and other markers of T cell inhibition and the content was significantly lower in EVs from RA PBMCs than HC PBMCs. Stimulation of the cells increased the miRNA expression. However, EVs isolated from stimulated RA SFMCs did not change their miRNA expression profile to the same extend.

Conclusion

EVs carrying both the PD-1 receptor and miRNAs associated with T cell inhibition were present in RA cell cultures. Upon stimulation, these miRNAs failed to be upregulated in EVs from RA SFMCs. This was in line with increased expression of T cell co-inhibitory markers on SFMCs. In conclusion, we suggest EVs to play a significant role in the RA microenvironment, potentially favoring the progression of T cell exhaustion.

Soluble programmed death-1 levels are associated with disease activity and treatment response in patients with autoimmune hepatitis

PURPOSE

Autoimmune hepatitis (AIH) is a chronic liver disease caused by impaired immune regulation. Programmed death-1 (PD-1) is an inhibitory receptor mainly expressed by T cells and with its ligands, PD-L1 and PD-L2 present on antigen-presenting cells. We hypothesised the PD-1 axis to be impaired in AIH and investigated systemic levels of soluble(s) PD-1 and T cells ability to up-regulate PD-1 following in vitro activation in AIH patients.

MATERIALS AND METHODS

We included 67 AIH patients; 9 with active disease, 31 responders and 27 incomplete-responders to standard therapy. Forty-seven healthy controls (HC) were included for comparison. Soluble PD-1 was measured by enzyme-linked immunosorbent assay. The PD-1 expression on T cells was measured using flow cytometry before and after 48-h stimulation in vitro with CD3/CD28 in 13 AIH patients and 10 HC.

RESULTS

Soluble PD-1 was significantly elevated in AIH patients with active disease [0.24 ng/mL (range 0.16-0.28)] and in incomplete responders to standard therapy [0.17 (0.11-0.22)] compared with responders [0.11 (0.08-0.16), p = .008 and p = .01, respectively] and HC [0.12 (0.05-0.16), p = .02, both]. Following in vitro activation, PD-1 was significantly up-regulated (3.3-fold) on CD4⁺ T cells from AIH patients compared with HC (1.5-fold) (p = .0006).

CONCLUSIONS

AIH patients with active disease and incomplete response to standard treatment have similarly increased sPD-1 levels. Further, AIH patients have increased ability to up-regulate PD-1 following in vitro activation. Together these data suggests an impaired PD-1 axis in AIH.

Increased soluble programmed death-1 (sPD-1) is associated with disease activity and radiographic progression in early rheumatoid arthritis

OBJECTIVES

Programmed death-1 (PD-1) is an immunoregulatory molecule functioning by down-regulating immune responses. PD-1 is present on follicular helper T cells (TFH) and is important in the formation of plasma cells. PD-1 exists in a bioactive soluble form (sPD-1) and is thought to be implicated in disease activity in chronic rheumatoid arthritis (RA).

METHOD

We measured sPD-1 at baseline and 9 months after treatment initiation in plasma from early RA patients (n = 34). We tested for correlations with the Disease Activity Score using 28 joint counts (DAS28), the Health Assessment Questionnaire (HAQ) score, immunoglobulin M rheumatoid factor (IgM-RF), anti-cyclic citrullinated peptide (anti-CCP) antibodies, C-reactive protein (CRP), interleukin-21 (IL-21), and total Sharp score (TSS). We also measured sPD-1 in plasma from healthy volunteers (HV) (n = 20) and in plasma and synovial fluid (SF) from patients with chronic RA (> 8 years of disease, n = 30). We further investigated the cellular expression of PD-1 and its ligand PD-L1.

RESULTS

sPD-1 concentrations in early [median 0.421 ng/mL, interquartile range (IQR) 0.04-2.560 ng/mL] and chronic (median 0.239 ng/mL, IQR 0.184-0.584 ng/mL) RA were increased compared with HV (median 0.04 ng/mL, IQR 0.04-0.04 ng/mL) (all p < 0.005). In early RA the change in sPD-1 was associated with DAS28 (r = 0.363, p < 0.05) and HAQ score (r = 0.554, p < 0.05) and inversely with TSS at 3-5 years (r = -0.468, p < 0.05). sPD-1 concentration correlated with IgM-RF, anti-CCP antibodies, and IL-21 (all p < 0.05). PD-1 was primarily expressed by synovial memory T cells whereas PD-L1 was mainly expressed by synovial monocytes.

CONCLUSIONS

The significantly elevated plasma levels of sPD-1 in early RA, the association with core disease parameters, and the inverse correlation with TSS suggest that sPD-1 is an important mediator in inflammatory and radiographic disease progression.

Soluble macrophage-derived CD163 is a marker of disease activity and progression in early rheumatoid arthritis

OBJECTIVES

To investigate the expression of the soluble form of the resident macrophage marker CD163 (sCD163) and its association with core parameters for disease activity, including radiographic progression in early rheumatoid arthritis (RA).

METHODS

In a longitudinal sample set from early RA patients (n=34) we measured plasma levels of sCD163 at initiation of treatment and after 9 months of treatment and correlated levels with disease activity in 28 joints (DAS28), C-reactive protein (CRP), erythrocyte sedimentation rate (ESR) and total Sharp score (TSS). We also measured plasma levels of sCD163 in 55 healthy volunteers (HV) and in a transverse sample set of chronic (>8 years of disease) RA patients (n=24) and OA patients (n=24) with paired plasma and joint fluid.

RESULTS

Early RA patients had significantly higher plasma levels of sCD163 (1.69mg/l (1.42-2.10)) (median (IQR)) at baseline than after 9 months of treatment (1.28mg/l (0.963-1.66), p=0.001), but not significantly changed compared with HV (1.66mg/l (1.22-2.02)). In early RA patients, baseline levels of sCD163, correlated with DAS28, CRP and ESR. Interestingly, sCD163 at 9 months was associated with radiographic progression (TSS) between year 0 and 5 (r=0.468, p=0.02). Levels of sCD163 were higher in RA patients, than in OA patients and higher in SF than in plasma.

CONCLUSIONS

Plasma levels of macrophage derived sCD163 are associated with disease activity and predict radiographic progression in early RA patients, supporting that sCD163 may have a role as a biomarker of disease activity and that resident macrophages are important for joint destruction.