Serum immunoglobulin free light chain assessment in rheumatoid arthritis and primary Sjogren's syndrome

Diffuse large B cell lymphoma in rheumatoid arthritis patients is associated with elevated B-cell driving factors including CXCL13

Patients with rheumatoid arthritis (RA) are at increased risk of diffuse large B cell lymphoma (DLBCL) compared to the general population. Here, we explored the inflammatory profiles in the blood of RA patients who had developed DLBCL. RA-DLBCL patients had significantly higher levels of the pro-inflammatory markers TNF, IL-8, CXCL9, APRIL, and particularly CXCL13 (median 796 vs. 206 pg/mL, p = 0.001), compared to RA controls. By including an extensive autoantibody panel of rheumatoid factor, IgG anti-CCP2, anti-citrullinated protein antibodies (ACPA) fine-specificities, and other anti-modified protein antibodies, all RA-DLBCL patients were autoantibody seropositive. Yet, RA-DLBCL patients did not display significantly different autoantibody signatures compared to RA controls. The levels of immunoglobulin free light chains and C-reactive protein were similar in RA-DLBCL patients and RA controls. In conclusion, RA-DLBCL patients exhibit pro-inflammatory signatures with elevated markers that are important for B cells and may contribute to enhanced B-cell activation and promote lymphoma development.

Derangements of immunological proteins in HIV-associated diffuse large B-cell lymphoma: the frequency and prognostic impact

Introduction

Diffuse large B-cell lymphoma (DLBCL) is an aggressive malignancy of B-cells frequently encountered among people living with HIV. Immunological abnormalities are common in immunocompetent individuals with DLBCL, and are often associated with poorer outcomes. Currently, data on derangements of immunological proteins, such as cytokines and acute phase reactants, and their impact on outcomes in HIV-associated DLBCL (HIV-DLBCL) is lacking. This study assessed the levels and prognostic relevance of interleukin (IL)-6, IL-10 and Transforming Growth Factor Beta (TGFβ), the acute phase proteins C-reactive protein (CRP) and ferritin; serum free light chains (SFLC) (elevation of which reflects a prolonged pro-inflammatory state); and the activity of the immunosuppressive enzyme Indoleamine 2,3-dioxygenase (IDO)in South African patients with DLBCL.

Methods

Seventy-six patients with incident DLBCL were enrolled, and peripheral blood IL-6, IL-10, TGFβ, SFLC and IDO-activity measured in selected patients. Additional clinical and laboratory findings (including ferritin and CRP) were recorded from the hospital records.

Results

Sixty-one (80.3%) of the included patients were people living with HIV (median CD4-count = 148 cells/ul), and survival rates were poor (12-month survival rate 30.0%). The majority of the immunological proteins, except for TGFβ and ferritin, were significantly higher among the people living with HIV. Elevation of IL-6, SFLC and IDO-activity were not associated with survival in HIV-DLBCL, while raised IL-10, CRP, ferritin and TGFβ were. On multivariate analysis, immunological proteins associated with survival independently from the International Prognostic Index (IPI) included TGFβ, ferritin and IL-10.

Conclusion

Derangements of immunological proteins are common in HIV-DLBCL, and have a differential association with survival compared to that reported elsewhere. Elevation of TGFβ, IL-10 and ferritin were associated with survival independently from the IPI. In view of the poor survival rates in this cohort, investigation of the directed targeting of these cytokines would be of interest in our setting.

Free Light Chains κ and λ as New Biomarkers of Selected Diseases

Diagnostic and prognostic markers are necessary to help in patient diagnosis and the prediction of future clinical events or disease progression. As promising biomarkers of selected diseases, the free light chains (FLCs) κ and λ were considered. Measurements of FLCs are currently used in routine diagnostics of, for example, multiple myeloma, and the usefulness of FLCs as biomarkers of monoclonal gammopathies is well understood. Therefore, this review focuses on the studies concerning FLCs as new potential biomarkers of other disorders in which an inflammatory background has been observed. We performed a bibliometric review of studies indexed in MEDLINE to assess the clinical significance of FLCs. Altered levels of FLCs were observed both in diseases strongly connected with inflammation such as viral infections, tick-borne diseases or rheumatic disorders, and disorders that are moderately associated with immune system reactions, e.g., multiple sclerosis, diabetes, cardiovascular disorders and cancers. Increased concentrations of FLCs appear to be a useful prognostic marker in patients with multiple sclerosis or tick-borne encephalitis. Intensive synthesis of FLCs may also reflect the production of specific antibodies against pathogens such as SARS-CoV-2. Moreover, abnormal FLC concentrations might predict the development of diabetic kidney disease in patients with type 2 diabetes. Markedly elevated levels are also associated with increased risk of hospitalization and death in patients with cardiovascular disorders. Additionally, FLCs have been found to be increased in rheumatic diseases and have been related to disease activity. Furthermore, it has been suggested that inhibition of FLCs would reduce the progression of tumorigenesis in breast cancer or colitis-associated colon carcinogenesis. In conclusion, abnormal levels of κ and λ FLCs, as well as the ratio of κ:λ, are usually the result of disturbances in the synthesis of immunoglobulins as an effect of overactive inflammatory reactions. Therefore, it seems that κ and λ FLCs may be significant diagnostic and prognostic biomarkers of selected diseases. Moreover, the inhibition of FLCs appears to be a promising therapeutical target for the treatment of various disorders where inflammation plays an important role in the development or progression of the disease.

Gut mycobiome dysbiosis contributes to the development of hypertension and its response to immunoglobulin light chains

Objectives

Human gut microbiome has gained great attention for its proposed roles in the development of hypertension. The fungal microbiome in the human gut (i.e. the mycobiome) is beginning to gain recognition as a fundamental part of our microbiome. However, the existing knowledge of human mycobiome has never revealed the association between gut mycobiome and hypertension. It is known that inflammation and immunity contribute to human hypertension. Here, we sought to investigate whether gut mycobiome could predict the development of hypertension and its association with immunoglobulin light chains.

Methods and materials

Participants were classified into three cohorts: prehypertension (pre-HTN), hypertension (HTN), and normal-tension (NT) based on their blood pressure. Fresh samples were collected, and the ITS transcribed spacer ribosomal RNA gene sequence was performed. An immunoturbidimetric test was used to examine the serum levels of immunological light chains.

Results

Subjects in both of the states of pre-HTN and HTN had different fungal microbiome community compared to the NT group (FDR<0.05). Slightly higher levels of fungal richness and diversity were observed in the groups of pre-HTN and HTN. The relative abundance of Malassezia increased in the HTN group compared to that in the NT group, and the relative abundance of Mortierella enriched in the NT group. For the pre-HTN group, the relative abundance of Malassezia was positively associated with serum the concentration of light chain (LC) κ (r=0.510, P=0.044); for the HTN group, the relative abundance of Mortierella was positively associated with the serum concentration of LC κ (P<0.05), the relative abundance of Malassezia was positively associated with both the serum concentrations of LC κ and LC λ (r>0.30, P<0.05).

Conclusions

Our present study demonstrated that gut fungal dysbiosis occurred in the state of prehypertension, and fungal dysbiosis can predict the dysregulation of serum light chains in hypertension patients. Further study on modulating gut fungal community should be focused on balancing the immunological features in hypertension.

A Cohort Study of Free Light Chain Ratio in Combination with Serum Protein Electrophoresis as a First-Line Test in General Practice

Simple Summary

Multiple Myeloma (MM) can be a diagnostic challenge as it often presents with unspecific symptoms in patients in general practice. Serum-free light chain (sFLC) ratio is suggested to replace urine protein electrophoresis (UPE) in the diagnostic work-up of myeloma. We aimed to investigate the performance of the sFLC ratio in general practice (GP) compared to UPE in a low prevalence cohort of 13,210 patients from general practice. We found that sFLC ratio performs in line with UPE; however, we observed a pronounced number of false-positive tests. Therefore, local instrument-dependent adjustment of reference ranges/decision limits should be considered to avoid an unnecessarily high number of false-positive tests.

Abstract

Multiple Myeloma (MM) often present with unspecific symptoms, which can lead to diagnostic delay. Serum-free light chain (sFLC) ratio is suggested to replace urine protein electrophoresis (UPE) in the diagnostic work-up of myeloma. We aimed to investigate the performance of the sFLC-ratio in general practice (GP) compared to UPE, just as we explored different sFLC-ratio cut-offs’ influence on diagnostic values. In a cohort of 13,210 patients from GP measures of sFLC-ratio, serum protein electrophoresis (SPE), or UPE were compared to diagnoses of incident M-component related diseases acquired from Danish health registers. UPE and sFLC-ratio equally improved diagnostic values when combined with SPE (sensitivity: SPE and UPE: 95.6 (90.6–98.4); SPE and sFLC-ratio: 95.1 (90.2–98.0)). The addition of the sFLC-ratio to SPE resulted in the identification of 13 patients with MGUS, light chain disease and amyloidosis, which was in line with the addition of UPE to SPE. The number of false-positive tests was UPE and SPE: 364 (11%) and sFLC-ratio and SPE: 677(19%). Expanding sFLC-ratio reference range to 0.26–4.32 resulted in a significant reduction in false positives n = 226 (6%) without loss of patients with clinical plasma cell dyscrasias. sFLC-ratio improves the diagnostic value of SPE in GP. However, due to low specificity and a large number of false positives, expanded cut-off values should be considered.

Mono/polyclonal free light chains as challenging biomarkers for immunological abnormalities

Free light chain (FLC) kappa (k) and lambda (λ) consist of low molecular weight proteins produced in excess during immunoglobulin synthesis and secreted into the circulation. In patients with normal renal function, over 99% of FLCs are filtered and reabsorbed. Thus, the presence of FLCs in the serum is directly related to plasma cell activity and the balance between production and renal clearance. FLCs are bioactive molecules that may exist as monoclonal (m) and polyclonal (p) FLCs. These have been detected in several body fluids and may be key indicators of ongoing damage and/or illness. International guidelines now recommend mFLC for screening, diagnosis and monitoring multiple myeloma and other plasma cell dyscrasias. In current clinical practice, FLCs in urine indicate cast nephropathy and other renal injury, whereas their presence in cerebrospinal fluid is important for identifying central nervous system inflammatory diseases such as multiple sclerosis. Increased pFLCs have also been detected in various conditions characterized by B cell activation, i.e., chronic inflammation, autoimmune disease and HCV infection. Monitoring the coronavirus (COVID-19) pandemic by analysis of salivary FLCs presents a significant opportunity in clinical immunology worthy of scientific pursuit.

The role of serum free light chain as biomarker of Myasthenia Gravis

BACKGROUND AND AIM

Myasthenia gravis (MG) is a B lymphocyte-mediated disease affecting neuromuscular transmission. The clinical course of MG is unpredictable due to the fluctuating nature and heterogeneity of the disease. Increased levels of free light chains (FLC), which reflect B cell activation, have been detected in different autoimmune disorders. In this study, we evaluated the potential role of FLC as diagnostic and prognostic biomarkers of MG.

MATERIALS AND METHODS

74 MG patients and 52 healthy individuals were included in the study. Serum FLC levels were measured by turbidimetric assay (Freelite, The Binding Site Group Ltd) on the Optilite Analyser System in both groups. In MG patients, anti-AChR and anti-MuSK autoantibodies were detected by enzyme-linked immunosorbent assay.

RESULTS

MG patients displayed significantly higher serum κ and total FLC levels than controls, respectively for κFLC 16.0 vs 13.8 mg/L and for total FLC 29.8 vs 25.9 mg/L. Moreover, increased κFLC levels were observed in seropositive MG patients. No association was observed between serum FLC levels and clinical manifestations of disease as well as with severity, age at MG onset, thymoma and treatment.

CONCLUSION

Increased levels of κFLC and total FLC could serve as biomarkers to support the diagnosis of MG.

Combined serum free light chain predicts prognosis in acute kidney injury following cardiovascular surgery

Objectives

Increased polyclonal free light chains (FLCs) are found in inflammatory conditions. Inflammation is recognized in the progression of acute kidney injury (AKI). This study was aimed to determine whether polyclonal combined FLC (cFLC) was associated with prognosis of AKI patients.

Methods

This prospective cohort included 145 adults with hospital-acquired AKI following cardiovascular surgery between 2014 and 2016, according to the KDIGO creatinine criteria. The primary end point of the study was all-cause death during follow-up.

Results

The median of serum cFLC concentration in the cohort was 42.0 (31.9–60.3 mg/L) and levels of cFLC in patients with AKI stage 3 were higher than those in AKI stage 1 and stage 2. cFLC levels correlated significantly with renal function biomarkers, high sensitivity C-reactive protein (hsCRP), and sequential organ failure assessment (SOFA) score. Patients were organized into the following two groups: the low-cFLC group (cFLC <43.3 mg/L) and the high-cFLC group (cFLC ≥ 43.3 mg/L). A total of 17 (11.0%) patient deaths occurred within 90 d, 13 (18.8%) in the high-cFLC group. Kaplan–Meier analysis revealed that the two groups differed significantly with respect to 90-d survival (log-rank p = .012), and Cox regression analysis showed that an cFLC level ≥43.3 mg/L was significantly associated with a 5.0-fold increased risk of death (adjusted hazard ratio [HR], 5.95; 95% confidence interval [CI], 1.04– 33.91; p = .045) compared with an cFLC level <43.3 mg/L.

Conclusions

Serum cFLC levels were significantly elevated and might be an independent predictor of mortality in patients with AKI following cardiovascular surgery.

Salivary free light chains and salivary immunoglobulins as potential non-invasive biomarkers in primary Sjögren's syndrome

BACKGROUND

B cells contribute significantly to the pathogenesis of primary Sjögren's syndrome (pSS). Free light chains (FLCs) are generated during the production of immunoglobulins (Igs) and are surrogates of B cell activity. We hypothesized that salivary FLCs and salivary Igs could represent salivary gland inflammation and therefore, serve as biomarkers in pSS.

METHODS

Patients >18 years old fulfilling the American College of Rheumatology / European League Against Rheumatism (EULAR) 2016 criteria for pSS and age-matched healthy and disease controls (sicca non-pSS, rheumatoid arthritis, systemic lupus erythematosus) were recruited for this cross-sectional study. FLCs in saliva and serum were measured by immunoturbidimetry. Serum and salivary Igs were measured by nephelometry and enzyme-linked immunosorbent assay, respectively. Area under the receiver operator characteristic curve was determined. The factors influencing the serum and salivary FLCs in pSS were determined using backward linear regression.

RESULTS

A total of 78 patients with pSS, 76 healthy controls and 62 disease controls were recruited. Median EULAR SS disease activity index (interquartile range) was 1 (3.75). Serum FLCκ and FLCλ, salivary FLCλ, serum and salivary IgG, salivary IgM was significantly higher in the pSS group compared to the controls. Areas under the curve for salivary FLCλ, serum FLCκ, serum and salivary IgG were 0.75, 0.72, 0.78 and 0.77, respectively. Regression analysis showed that salivary FLCκ, salivary FLCλ and salivary IgG were associated with positive salivary gland histopathology. Use of immunosuppressants and glucocorticoids was associated with lower values of salivary parameters.

CONCLUSION

Salivary FLCλ and salivary IgG were significantly different between pSS and control groups and could be potential non-invasive biomarkers in pSS. These findings should be confirmed in larger longitudinal studies.

Hematological and Genetic Markers in the Rational Approach to Patients With HCV Sustained Virological Response With or Without Persisting Cryoglobulinemic Vasculitis

BACKGROUND AND AIMS

Direct-acting antivirals (DAAs) usually lead to improvement/remission of cryoglobulinemic vasculitis (CV), although symptoms may persist/recur after a sustained virological response (SVR). We evaluated hematological and genetic markers in patients with HCV-SVR vasculitis with and without persisting/recurring symptoms to early predict the CV outcome.

APPROACH AND RESULTS

Ninety-eight patients with HCV-CV were prospectively enrolled after a DAA-induced SVR: Group A: 52 with complete clinical response; Group B: 46 with symptom maintenance/recurrence. Monoclonal B-cell lymphocytosis, t(14;18) translocation, and abnormal free light chains κ/λ ratios were detected by flow cytometry or nested-PCR or nephelometry in 4% Group A versus 17% Group B (P = 0.04) patients, 17% Group A versus 40% Group B patients (P = 0.02), and 17% Group A versus 47% Group B (P = 0.003) patients, respectively. At least 1 out of 3 clonality markers was altered/positive in 29% of Group A versus 70% of Group B patients (P < 0.0001). When available, pretherapy samples were also tested for t(14;18) translocation (detected in 12/37 [32%] Group A and 21/38 [55%] Group B) and κ/λ ratios (abnormal in 5/35 [14%] Group A and 20/38 [53%] Group B) (P = 0.0006), whereas at least one clonality marker was detected/altered in 16/37 (43%) Group A and 30/38 (79%) Group B (P = 0.002). CV-associated single-nucleotide polymorphisms were tested by real-time PCR. Among them, notch4 rs2071286 T minor allele and TT genotype showed a higher frequency in Group B versus Group A (46% vs. 29%, P = 0.01, and 17% vs. 2%, P = 0.006, respectively).

CONCLUSIONS

Hematological or genetic analyses could be used to foresee the CV clinical response after DAA therapy and could be valuable to assess a rational flowchart to manage CV during follow-up.

Cell Population Data and Serum Polyclonal Immunoglobulin Free Light Chains in the Assessment of COVID-19 Severity

Distinguishing between severe and nonsevere COVID-19 to ensure adequate healthcare quality and efficiency is a challenge for the healthcare system. The aim of this study was to assess the usefulness of CBC parameters together with analysis of FLC serum concentration in risk stratification of COVID-19. Materials and methods: CBC was analyzed in 735 COVID ICU, COVID non-ICU, and non-COVID ICU cases. FLC concentration was analyzed in 133 of them. Results: COVID ICU had neutrophils and lymphocytes with the greatest size, granularity, and nucleic acid content. Significant differences in concentrations of κ and λ FLCs were shown between COVID ICU and COVID non-ICU. However, no difference was found in the κ/λ ratio between these groups, and the ratio stayed within the reference value, which indicates the presence of polyclonal FLCs. FLC κ measurement has significant power to distinguish between severe COVID-19 and nonsevere COVID-19 (AUC = 0.7669), with a sensitivity of 86.67% and specificity of 93.33%. The κ coefficients’ odds ratio of 3.0401 was estimated. Conclusion: It can be concluded that the results obtained from the measure of free light immunoglobulin concentration in serum are useful in distinguishing between severe and nonsevere COVID-19.

Immune-Related Urine Biomarkers for the Diagnosis of Lupus Nephritis

The kidney is one of the main organs affected by the autoimmune disease systemic lupus erythematosus. Lupus nephritis (LN) concerns 30-60% of adult SLE patients and it is significantly associated with an increase in the morbidity and mortality. The definitive diagnosis of LN can only be achieved by histological analysis of renal biopsies, but the invasiveness of this technique is an obstacle for early diagnosis of renal involvement and a proper follow-up of LN patients under treatment. The use of urine for the discovery of non-invasive biomarkers for renal disease in SLE patients is an attractive alternative to repeated renal biopsies, as several studies have described surrogate urinary cells or analytes reflecting the inflammatory state of the kidney, and/or the severity of the disease. Herein, we review the main findings in the field of urine immune-related biomarkers for LN patients, and discuss their prognostic and diagnostic value. This manuscript is focused on the complement system, antibodies and autoantibodies, chemokines, cytokines, and leukocytes, as they are the main effectors of LN pathogenesis.

Rheumatologic diseases impact the risk of progression of MGUS to overt multiple myeloma

Monoclonal gammopathy of undetermined significance (MGUS), a premalignant condition, is associated with various chronic inflammatory rheumatic diseases (RDs) and is frequently observed as an incidental finding during routine work-up. The association of MGUS and chronic RDs is well established, but the impact of RDs on the risk of transformation into overt multiple myeloma (MM) has not been evaluated so far. MGUS patients diagnosed between January 2000 and August 2016 were identified and screened for concomitant RDs. RDs were grouped into antibody (Ab)-mediated RDs and non-Ab-mediated RDs (polymyalgia rheumatica, large-vessel giant cell arteritis, spondyloarthritis, and gout). Progression to MM was defined as a categorical (yes/no) or continuous time-dependent (time to progression) variable. Of 2935 MGUS patients, 255 (9%) had a concomitant RD. MGUS patients diagnosed with non-Ab-mediated RDs had a doubled risk of progression compared with those without a concomitant RD (hazard ratio, 2.1; 95% CI, 1.1-3.9; P = .02). These data translate into a 5-year risk of progression of 4% in MGUS patients without rheumatologic comorbidity, 10% in those with concomitant non-Ab-mediated RDS, and 2% in those with Ab-mediated RDs. By using the complex risk stratification model that includes myeloma protein (M-protein) concentration, immunoglobulin type, and level of free light chain ratio as variables, patients with non-Ab-mediated RDs (n = 57) had the highest risk for progression (hazard ratio, 6.8; 95% CI, 1.5-30.7; P = .01) compared with patients with Ab-mediated RDs (n = 77). Chronic inflammatory diseases have an impact on the risk of MGUS progressing into overt MM, with a doubled risk of transformation observed in patients with non-Ab-mediated RDs. Future research can elucidate whether comorbidities such as RDs should be included in currently applied prognostic MGUS scores.

Serum free light chain assessment in type 1 autoimmune pancreatitis

BACKGROUND

/Object: Some patients with type 1 autoimmune pancreatitis (AIP), the pancreatic manifestation of IgG4-related disease, have normal serum IgG4. The aim of this study is to investigate the diagnostic value of measuring serum free light chains (FLCs) in type 1 AIP.

MATERIALS AND METHODS

Thirty-seven patients with type 1 AIP, and 21 healthy, 17 alcoholic chronic pancreatitis (ACP), 21 idiopathic chronic pancreatitis (ICP) and 20 pancreatic cancer (PC) patients were enrolled. Serum IgG4 and FLC concentrations were measured using sFLC Freelite assays on a nephelometric analyzer.

RESULTS

Active AIP patients have significantly higher serum levels of κ (median 30.97 (12.3-227.0) mg/L) and λFLC (median 20.53 (12.36-102.7) mg/L)) than healthy controls (κFLC; median 12.5 (3.1-52.1) mg/L), λFLC: median 12.45 (5.4-39.5) mg/L) (p < 0.05) correlating with raised serum IgG4, and significantly higher summated FLCs (∑) (median 53.09 (25.0-218.0) mg/L) than ICP patients (median 26.77 (15.0-89.2) mg/L) and healthy controls (median 24.43 (8.5-91.6) mg/L) (p < 0.05). AIP patients (median 1.43 (0.84-3.24)) showed significantly higher κ/λ ratios than ACP (median 0.83 (0.42-1.18)), ICP (median 0.87 (0.47-2.16)), PC patients (median 0.90 (0.48-1.27)) and healthy controls (median 0.963 (0.51-1.32)). There was a correlation between increased κ and λ FLCs levels and the number of affected organs involved in IgG4 related disease.

CONCLUSION

Patients with type 1 AIP have increased serum k and λ FLC concentrations, Σ FLC, and κ/λ ratios. These novel biomarkers may be useful in the diagnosis of type 1 AIP and in monitoring disease activity.

New frontiers in precision medicine for Sjogren's syndrome

Introduction: Sjögren's syndrome is a unique systemic autoimmune disease, placed in the center of systemic autoimmunity and at the crossroads of autoimmunity and lymphoproliferation. The diverse clinical picture of the disease, the inefficacy of current biologic treatments, and the co-existence with lymphoma conferring to the patients' morbidity and mortality force the scientific community to review disease pathogenesis and reveal the major implicated cellular and molecular elements.Areas covered: Biomarkers for early diagnosis, prediction, stratification, monitoring, and targeted treatments can serve as a tool to interlink and switch from the clinical phenotyping of the disease into a more sophisticated classification based on the underlying critical molecular pathways and endotypes. Such a transition may define the establishment of the so-called precision medicine era in which patients' management will be based on grouping according to pathogenetically related biomarkers. In the current work, literature on Sjogren's syndrome covering several research fields including clinical, translational, and basic research has been reviewed.Expert opinion: The perspectives of clinical and translational research are anticipated to define phenotypic clustering of high-risk pSS patients and link the clinical picture of the disease with fundamental molecular mechanisms and molecules implicated in pathogenesis.

Air Pollution and Polyclonal Elevation of Serum Free Light Chains: An Assessment of Adaptive Immune Responses in the Prospective Heinz Nixdorf Recall Study

BACKGROUND

Residential exposure to air pollution (AP) has been shown to activate the immune system (IS). Although innate immune responses to AP have been studied extensively, investigations on the adaptive IS are scarce.

OBJECTIVES

The aim of this study was to investigate the association between short- to long-term AP exposure and polyclonal free light chains (FLC) produced by plasma cells.

METHODS

We used repeated data from three examinations (t0: 2000-2003; t1: 2006-2008; and t2: 2011-2015) of the population-based German Heinz Nixdorf Recall cohort of initially 4,814 participants (45-75 y old). Residential exposure to total and source-specific particulate matter (PM) with an aerodynamic diameter of 10 or 2.5μm (PM10 and PM2.5 respectively), nitrogen dioxide (NO2), and particle number concentrations (accumulation mode; PNAM) was estimated using a chemistry transport model with different time windows (1- to 365-d mean ± standard deviation) before blood draw. We applied linear mixed models with a random participant intercept to estimate associations between total, traffic- and industry-related AP exposures and log-transformed FLC, controlling for examination time, sociodemographic and lifestyle variables, estimated glomerular filtration rate and season.

RESULTS

Analyzing 9,933 observations from 4,455 participants, we observed generally positive associations between AP exposures and FLC. We observed strongest associations with middle-term exposures, e.g., 3.0% increase in FLC (95% confidence interval: 1.8%, 4.3%) per interquartile range increase in 91-d mean of NO2 (14.1μg/m³). Across the different pollutants, NO2 showed strongest associations with FLC, followed by PM10 and PNAM. Effect estimates for traffic-related exposures were mostly higher compared with total exposures. Although NO2 and PNAM estimates remained stable upon adjustment for PM, PM estimates decreased considerably upon adjustment for NO2 and PNAM.

DISCUSSION

Our results suggest that middle-term AP exposures in particular might be positively associated with activation of the adaptive IS. Traffic-related PM, PNAM, and NO2 showed strongest associations. https://doi.org/10.1289/EHP7164.

Idiopathic membranous nephropathy in a patient diagnosed with IgG4-related disease: A case report

RATIONALE

Immunoglobulin (Ig) G4-related disease (IgG4-RD) is a newly recognized, systemic disease. Membranous nephropathy is the most common glomerular lesion in IgG4- related kidney disease. However, the lack of relationship with IgG4-related kidney disease and monoclonal gammopathy of undetermined significance (MGUS) warrants investigation of the potential mechanisms.

PATIENT CONCERNS

A 62-year-old patient was diagnosed with IgG4-RD, tubulointerstitial nephritis, retroperitoneal fibrosis. After 2 years, she was presented with proteinuria, hypoproteinemia, facial, and bilateral lower limb edema. Furthermore, this patient exhibited deposits of IgG k of monoclonal hyperplasia, and bone marrow plasma cell count was 2.5%.

DIAGNOSIS

The patient was diagnosed with nephrotic syndrome, acute kidney injury, and MGUS. The pathological diagnosis was IgG4-related tubulointerstitial nephritis, IgG4-related membranous nephropathy.

INTERVENTIONS

The patient was treated with intravenous methylprednisolone (40 mg daily), which was changed to oral prednisone 50 mg/d after 2 months.

OUTCOMES

After 1 month, the patient exhibited a rapid response only with corticosteroid, and experienced partial remission of serum albumin and proteinuria.

LESSONS

This case may suggest a possible relationship between IgG4-RD and MGUS, provide some guidance for investigating the mechanism between them.

High κ free light chain is a potential biomarker for double seronegative and ocular myasthenia gravis

OBJECTIVE

To investigate the hypothesis that free light chain (FLC) sera levels could serve as a biomarker for myasthenia gravis (MG), especially for the subgroups of seronegative MG and ocular MG.

METHODS

Sera from 73 patients with MG (20 seronegative for antiacetylcholine receptor [AChR] and anti-muscle-specific kinase and 53 positive for anti-AChR, which were clinically divided into 24 patients with ocular type, 45 with generalized type, and 4 with unequivocal clinical manifestation) and 49 healthy controls were studied for κ FLC and λ FLC levels with the Freelite human FLC kits.

RESULTS

The κ but not the λ levels of FLC were significantly increased in the patients with MG, including those with double seronegative MG and ocular MG, compared with the healthy controls. The specificity for double seronegative MG and ocular MG were both 98.0% when κ FLC was ≥25.0 mg/L. Increased κ FLC levels were not affected by the patient's sex, age at MG onset, the presence of thymic pathology, or different treatments.

CONCLUSIONS

Elevated serum κ FLC may serve as a biomarker for MG in suspected patients who are double seronegative and in those with only ocular manifestations when serology is inconclusive.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that high κ FLC levels distinguished patients with MG, including those who were double seronegative, from healthy controls.

Serum immunoglobulin free light chain levels in systemic autoimmune rheumatic diseases

Several reports have highlighted the abnormal increments of serum immunoglobulin free light chains (FLCs) in the course of systemic autoimmune rheumatic diseases (SARD), but a comparative analysis among different conditions is still lacking. A strong association between elevated FLC and hepatitis C virus (HCV)-related mixed cryoglobulinaemia (HCVMC) has been well established. Here, we aimed to analyse serum FLC levels in patients with four different SARD in comparison with HCVMC. Using a turbidimetric assay, free κ and λ chains were quantified in sera from 198 SARD patients (37 rheumatoid arthritis, RA; 47 systemic lupus erythematosus, SLE; 52 anti-phospholipid syndrome, APS; 62 primary Sjogren's syndrome, pSS), 62 HCVMC and 50 healthy blood donors (HD). All patient groups showed increased κ levels when compared to HD: 33·5 ± 2·6 mg/l in HCVMC, 26·7 ± 2·3 mg/l in RA, 29·7 ± 1·9 mg/l in SLE, 23·8 ± 1·1 mg/l in APS, 24·2 ± 1·1 mg/l in pSS; 10·1 ± 0·6 mg/l in HD. Free λ levels displayed a significant increase only for HCVMC (20·4 ± 1·4 mg/l) and SLE (18·4 ± 1·0 mg/l) compared to HD (13·6 ± 0·9 mg/l). The increase of κ compared to λ takes into account a κ /λ ratio of 1·6 for all groups. Our results substantially analyse and strengthen the association between FLC and SARD focusing the questions regarding their role in the pathogenesis and diagnosis of human diseases. Unfortunately, the biochemical differences distinguishing normal from pathological FLC have not been identified. Production of different isotypes is probably connected to still-unknown pathways.

Comparative Proteomic Analysis of Serum from Pigs Experimentally Infected with Trichinella spiralis, Trichinella britovi, and Trichinella pseudospiralis

Although the available proteomic studies have made it possible to identify and characterize Trichinella stage-specific proteins reacting with infected host-specific antibodies, the vast majority of these studies do not provide any information about changes in the global proteomic serum profile of Trichinella-infested individuals. In view of the above, the present study aimed to examine the protein expression profile of serum obtained at 13 and 60 days postinfection (d.p.i.) from three groups of pigs experimentally infected with Trichinella spiralis, Trichinella britovi, and Trichinella pseudospiralis and from uninfected, control pigs by two-dimensional gel electrophoresis (2-DE) followed by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. The comparative proteomic analysis of the T. spiralis group vs. the control group revealed 5 differently expressed spots at both 13 and 60 d.p.i. Experimental infection with T. britovi induced significant expression changes in 3 protein spots at 13 d.p.i. and in 6 protein spots at 60 d.p.i. in comparison with the control group. Paired analyses between the group infected with T. pseudospiralis and the uninfected control group revealed 6 differently changed spots at 13 d.p.i. and 2 differently changed spots at 60 d.p.i. Among these 27 spots, 15 were successfully identified. Depending on the Trichinella species triggering the infection and the time point of serum collection, they were IgM heavy-chain constant region, antithrombin III-precursor, immunoglobulin gamma-chain, clusterin, homeobox protein Mohawk, apolipoprotein E precursor, serum amyloid P-component precursor, Ig lambda chains, complement C3 isoform X1, and apolipoprotein A-I. Our results demonstrate that various Trichinella species and different phases of the invasion produce a distinct, characteristic proteomic pattern in the serum of experimentally infected pigs.

Mass spectrometry-based metabolomics for irritable bowel syndrome biomarkers

BACKGROUND

Irritable bowel syndrome (IBS) is a common gastrointestinal disorder without obvious structural abnormalities or consistent associated biomarkers, making its diagnosis difficult. In the present study, we used a urine-based metabolomics approach to identify IBS biomarkers.

METHODS

We used an ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS) on urine samples from patients suffering from IBS and healthy controls. Data were coupled for multivariate statistical analysis methods.

RESULTS

We selected 30 differential metabolites associated with IBS and found steroid hormone biosynthesis and histidine metabolism alterations in patients with IBS that may be involved in the pathogenesis of the disease. In addition, we identified a panel of five metabolite markers composed of cortisone, citric acid, tiglylcarnitine, N6,-N6,-N6-trimethyl-L-lysine and L-histidine that could be used to discriminate between patients and healthy controls and may be appropriate as IBS diagnosis biomarkers.

CONCLUSION

Our findings indicate that metabolomics combined with pattern recognition can be useful to identify disease diagnostic IBS markers.

CLINICAL TRIAL REGISTRATION

ChiCTR1800020072.

No Evidence of Systemic Inflammation in Symptomatic Patients With Femoroacetabular Impingement

Femoroacetabular impingement (FAI) is a common cause of hip pain and represents a major cause of early osteoarthritis. The role of systemic inflammation in pre-arthritic hip conditions remains largely unknown and uninvestigated. Serum-free light chains (sFLCs) are inflammatory markers produced by B cells. This study aimed to determine whether there was evidence of systemic inflammation in patients with FAI, defined by sFLCs, and whether this correlated with markers of disease severity. Participants for this study were recruited from a single center (Nuffield Orthopedic Center, Oxford) and were taking part in the Femoroacetabular Impingement Trial. The cohort comprised 115 individuals (38 male, 77 female, mean age 37 years): 57 individuals received surgical intervention and 58 received physiotherapy. All individuals provided patient-reported outcome measures and serum samples at baseline and follow-up 8 months post-randomization. sFLC concentrations were measured in serum samples by immunoturbidimetry. At baseline, for all individuals, mean polyclonal sFLC concentrations were 30.36 mg/l (standard deviation [SD] 9.23). At follow-up, the mean polyclonal sFLC concentrations were 31.68 mg/l (SD 9.61) in the surgical intervention cohort, and 29.48 mg/l (SD 7.85) in the physiotherapy intervention cohort. There was no significant correlation between sFLC concentrations and any of the patient reported outcome measures, or radiographic measures: average or maximum alpha angle, or center edge angle. In conclusion, in patients with symptomatic FAI there was no systemic inflammation, as defined by sFLC concentrations, and no correlation between sFLC concentrations and measures of disease severity. The lack of inflammation suggests FAI is a mechanical phenomenon. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2189-2196, 2019.

Free light chains and autoimmunity

The study of free light chains (FLCs) has grown as area of enormous interest for many clinicians with the aim of disclosing the exact biological role and potential use of FLCs in the clinical routine. Moreover, the attention given to immunological functions of FLCs has sparked a new light into their pathogenic contribution in different chronic autoimmune-based inflammatory diseases. The release of intracellular antigens following cell death or ineffective clearance of apoptotic debris, modification of self-antigens, and molecular mimicry may trigger the production of immunoglobulins after activation and polyclonal expansion of B cells, by which FLCs are released. The discovery of polyclonal FLCs as potential biomarkers started with the observation of their increased concentrations in a variety of biological fluids related to patients with autoimmune diseases. This review deals with the use of polyclonal FLCs for identifying severity and monitoring outcome after treatment in some autoimmune diseases, namely systemic lupus erythematosus, myasthenia gravis, systemic sclerosis, rheumatoid arthritis and Sjögren's syndrome, as supported by the fact that levels of FLCs correlate with both B cell activation markers and other specific markers of disease activity. In a near future, following the evidence shown, FLCs might probably work as early prognostic markers of severity and also as indicators of response to treatment or early assessment of relapse in selected autoimmune diseases.

Serum markers of B-cell activation in pregnancy during late gestation, delivery, and the postpartum period

PROBLEM

B cells are vital for the normal evolution of pregnancy due to their humoral and possible regulatory activities. Our group and others have documented that circulating B-cell subsets undergo changes from normal late pregnancy to the postpartum period. However, the underlying mechanisms are poorly understood. Therefore, this study examined the degree of B-cell activation in normal pregnancy by analyzing the levels of serum markers in healthy pregnant women during the third trimester of pregnancy, the day of delivery, and the postpartum period.

METHOD OF STUDY

A prospective study including pregnant and non-pregnant women attending routine care was undertaken at a hospital clinic. Sociodemographic and clinical data were collected, along with peripheral blood samples. The serum levels of soluble CD23 (sCD23), B-cell-activating factor (BAFF), kappa (κ) and lambda (λ) free light chains (FLC), IgA, IgG, and IgM were quantified.

RESULTS

Our study included 43 third trimester pregnant and 35 non-pregnant women. In the pregnant women, the median levels of sCD23, BAFF, IgG, and κ FLC were significantly higher during the postpartum period than during the third trimester of pregnancy. Compared to the non-pregnant women, the third trimester pregnant women had higher median BAFF levels and lower sCD23, IgA, IgG, and FLC levels.

CONCLUSION

Changes in serum markers of B-cell kinetics that occur during pregnancy often persist into the postpartum period and affect the secretion of immunoglobulins from different classes. Further studies are needed to clarify the biological significance of our observations.

Synovial fluid proteome changes in ACL injury-induced posttraumatic osteoarthritis: Proteomics analysis of porcine knee synovial fluid

Surgical transection of the anterior cruciate ligament (ACL) in the porcine model leads to posttraumatic osteoarthritis if left untreated. However, a recently developed surgical treatment, bridge-enhanced ACL repair, prevents further cartilage damage. Since the synovial fluid bathes all the intrinsic structures of knee, we reasoned that a comparative analysis of synovial fluid protein contents could help to better understand the observed chondroprotective effects of the bridge-enhanced ACL repair. We hypothesized that post-surgical changes in the synovial fluid proteome would be different in the untreated and repaired knees, and those changes would correlate with the degree of cartilage damage. Thirty adolescent Yucatan mini-pigs underwent unilateral ACL transection and were randomly assigned to either no further treatment (ACLT, n = 14) or bridge-enhanced ACL repair (BEAR, n = 16). We used an isotopically labeled high resolution LC MS/MS-based proteomics approach to analyze the protein profile of synovial fluid at 6 and 12 months after ACL transection in untreated and repaired porcine knees. A linear mixed effect model was used to compare the normalized protein abundance levels between the groups at each time point. Bivariate linear regression analyses were used to assess the correlations between the macroscopic cartilage damage (total lesion area) and normalized abundance levels of each of the identified secreted proteins. There were no significant differences in cartilage lesion area or quantitative abundance levels of the secreted proteins between the ACLT and BEAR groups at 6 months. However, by 12 months, greater cartilage damage was seen in the ACLT group compared to the BEAR group (p = 0.005). This damage was accompanied by differences in the abundance levels of secreted proteins, with higher levels of Vitamin K-dependent protein C (p = 0.001), and lower levels of Apolipoprotein A4 (p = 0.021) and Cartilage intermediate layer protein 1 (p = 0.049) in the ACLT group compared to the BEAR group. There were also group differences in the secreted proteins that significantly changed in abundance between 6 and 12 months in ACLT and BEAR knees. Increased concentration of Ig lambda-1 chain C regions and decreased concentration of Hemopexin, Clusterin, Coagulation factor 12 and Cartilage intermediate layer protein 1 were associated with greater cartilage lesion area. In general, ACLT knees had higher concentrations of pro-inflammatory proteins and lower concentrations of anti-inflammatory proteins than BEAR group. In addition, the ACLT group had a lower and declining synovial concentrations of CILP, in contrast to a consistently high abundance of CILP in repaired knees. These differences suggest that the knees treated with bridge-enhanced ACL repair may be maintaining an environment that is more protective of the extracellular matrix, a function which is not seen in the ACLT knees.

Discovery of restless legs syndrome plasmatic biomarkers by proteomic analysis

OBJECTIVES

Restless legs syndrome (RLS) can lead to severe clinical consequences, thus negatively impacts on patients' overall health and quality of life. Nevertheless, the pathophysiology of RLS is still unclear, resulting in underestimate, incorrect, or ignored diagnosis and in limited management and treatment. The aim of this study was to compare the plasma proteome of RLS patients and healthy controls, in the search of diagnostic biomarkers related to the disease severity.

MATERIALS AND METHODS

Two-dimensional gel electrophoresis coupled with liquid chromatography-mass spectrometry was employed to analyze plasma samples of 34 patients with primary RLS, divided into two subgroups according to the disease severity: MMS group (mild-moderate symptoms) and HS group (severe and very severe symptoms), and 17 age- and sex-matched control subjects. Sleep quality, daytime sleepiness, and the level of depression were also evaluated.

RESULTS

We identified eight upregulated spots, corresponding to five unique proteins, in both RLS group vs. controls (alpha-1B-glycoprotein, alpha-1-acid glycoprotein 1, haptoglobin, complement C4-A, and immunoglobulin kappa constant); five increased spots, consistent with three unique proteins, only in HS-RLS (kininogen-1, immunoglobulin heavy constant alpha 1, and immunoglobulin lambda constant 2); one downregulated spot in both patient's groups (complement C3) and another one only in HS-RLS (alpha-1-antitrypsin).

CONCLUSIONS

The significantly different plasma proteins detected in RLS were mainly associated with inflammation, immune response, and cardiovascular disorders. Particularly, the gradual increasing in immunoglobulins could be indicative of the disease severity and evolution. Accordingly, these proteins may represent a valid set of useful biomarkers for RLS diagnosis, progression and treatment.

Identification of serum proteome signature of irritable bowel syndrome: Potential utility of the tool for early diagnosis and patient's stratification

Irritable bowel syndrome (IBS) is a chronic gastrointestinal disorder with high incidence, and great heterogeneity of symptoms. Numerous factors are correlated with IBS development; however, the pathophysiology is not yet clear. In addition, there is no appropriate diagnostic tool available. The aim of this study was the identification of protein expression alterations in IBS patients compared to healthy individuals. Serum samples from 30 IBS patients (10 with IBS-Diarrhea, 10 IBS-Constipation and 10 IBS-Mixed) and 10 healthy individuals were subjected to proteomic analysis by 2-dimensional gel electrophoresis. Following evaluation of densitometrical data, protein spots exhibiting differential expression among the groups, were further characterized by matrix-assisted laser desorption tandem time-of-flight mass spectrometer and the results were confirmed by Western blot analysis. Eight significantly different expressed proteins were identified. Seven of them were overexpressed in IBS cases and only one was overexpressed in healthy individuals. These proteins were also differently expressed between the three IBS subgroups. IBS-D group overexpressed immunoglobulin light chain Lambda (LAC3) and apolipoprotein E (APOE), IBS-C group overexpressed apolipoprotein H (APOH) and collagen alpha-1 (XIV) chain (COEA1), and IBS-M group and healthy individuals overexpressed retinol-binding protein 4 (RET4). Our results show a different serum protein profile of IBS patients compared to healthy controls. Understanding the role of these eight proteins which are differently expressed in IBS patients, may contribute to a better clarification of IBS pathogenesis and to patient's stratification.

SIGNIFICANCE

Irritable bowel syndrome (IBS) is a chronic gastrointestinal disorder with high incidence and great heterogeneity of symptoms without any appropriate diagnostic tool available. Eight significantly different expressed proteins were identified. Seven of them were overexpressed in IBS cases and only one was expressed in healthy individuals. These proteins were also differently expressed between the three IBS subgroups. Our results show that there is a different serum proteome signature in IBS compared to healthy individuals, as well as in IBS subgroups that could be used in the future for patient's stratification and as a diagnostic tool.

Serological Immunoglobulin-Free Light Chain Profile in Myasthenia Gravis Patients

Background

Serological levels of free immunoglobulin light chains (FLCs), produced in excess of heavy chains during synthesis of immunoglobulins by plasma cells, can be considered a direct marker of B cell activity in different systemic inflammatory-autoimmune conditions and may represent a useful predictor of rituximab (RTX) therapeutic efficacy, as reported for rheumatoid arthritis and systemic lupus erythematosus. Myasthenia gravis (MG) is an autoimmune disease of the neuromuscular junction with antibodies (abs) targeting the acetylcholine receptor (AChR) or the muscle-specific tyrosine kinase (MuSK), inducing muscle weakness and excessive fatigability. As MG course may be remarkably variable, we evaluated the possible use of FLCs as biomarkers of disease activity.

Subjects and Methods

We assessed FLC levels in 34 sera from 17 AChR-MG and from 13 MuSK-MG patients, in comparison with 20 sera from patients with systemic autoimmune rheumatic diseases and 18 from healthy blood donors, along with titers of specific auto-abs and IgG subclass distribution.

Results

We found a statistically significant increase in free κ chains in both AChR- and MuSK-MG patients, while free λ chain levels were increased only in AChR-MG. We also observed a significant reduction of both free κ and λ chains in 1/4 MuSK-MG patients along with specific abs titer, two months after RTX treatment.

Conclusions

From our data, FLCs appear to be a sensitive marker of B cell activation in MG. Further investigations are necessary to exploit their potential as reliable biomarkers of disease activity.

Free light chains of immunoglobulins in patients with systemic sclerosis: correlations with lung involvement and inflammatory milieu

AIM

Humoral immunity and B cells are thought to play an important role in the pathophysiology of the systemic sclerosis (SSc). The production of free light chains (FLC) of immunoglobulins is abnormally high in several pathological autoimmune conditions and reflects B cell activation. Furthermore, FLCs demonstrated different biological activities including their capability to modulate the immune system, proteolytic activity and complement cascade activation. The aims of this study are to determine the FLC levels in patients with SSc compared with healthy controls (HC) and to study their possible association with organ involvement and disease characteristics.

METHODS

Sixty-five patients with SSc and 20 HC were studied. Clinical and immunological inflammatory characteristics were assessed for all the patients with SSc. κ-FLC and λ-FLC, interleukin 6 (IL-6) and B cell activating factor levels were measured.

RESULTS

The mean serum κ-FLC levels and FLC ratio were significantly higher in patients with SSc compared with HC, while the serum λ-FLC levels were comparable.The levels of FLC were comparable in patients with diffuse skin disease and limited skin involvement, while κ-FLC levels were increased in patients with restrictive lung (forced vital capacity (FVC) <80%) disease (26.4±7.4 mg/L) when compared with patients with FVC ≥80% (19.6±7.3 mg/L, P=0.009). In patients with SSc, the levels of serum κ-FLC level directly correlated with the IL-6 levels (R=0.3, P=0.001) and disease activity (R=0.4, P=0.003).

CONCLUSIONS

FLC levels are elevated in SSc and high levels are associated with lung involvement and with a higher degree of inflammation, supporting a possible role of B cell activation in the pathophysiology of the disease.

An unusual case of chronic lymphocytic leukemia, multiple myeloma and cardiac amyloidosis

Light chain amyloidosis has very rarely been reported in association with chronic lymphocytic leukemia (CLL). We reported on a 76-years-old female who presented with simultaneous kappa-restricted chronic lymphocytic leukemia (CLL) and a lambda-restricted multiple myeloma with plasma cells causing AL amyloidosis involving the heart. While monoclonal immunoglobulins occasionallyproduced by CLL have previously been implicated in AL amyloidosis, there only a few cases reported of AL amyloidosis resulting from a distinct plasma cell dyscrasia that is not clonally related to the concurrent CLL.

Free light chains: Eclectic multipurpose biomarker

The production of antibodies is accompanied by a slight excess of synthesis of κ and λ immunoglobulin light chains; small amounts of them are released in the peripheral blood and can also be found in various body fluids, such as synovial fluid, cerebrospinal fluid, urine and saliva. They are rapidly filtered by the glomerulus and >99% are reabsorbed from the cells of the proximal convoluted tubule, making them present in the urine in only trace amounts. The production of an excess of protein without a reason or a specific function in a biological system is rare. Free light chains, considered for years a waste product of Ig synthesis, are currently known to be very active molecules, able to bind antigens as well as whole immunoglobulin and helping to develop specific antibody affinity. The ability of free light chains to activate mast cells and then become an active part of the pathogenic mechanisms of chronic inflammatory diseases has increased interest in their clinical use, both as an attractive therapeutic target or as a biochemical marker of disease evolution or remission. This is an overview of relevant scientific interest that immunoglobulin light chains κ and λ have attracted over the years, a report on the progress in knowledge about their structure and function, with a special focus on their biological meaning and potential clinical utility in different diseases.

Human neonatal thymectomy induces altered B-cell responses and autoreactivity

An association between T‐cell lymphopenia and autoimmunity has long been proposed, but it remains to be elucidated whether T‐cell lymphopenia affects B‐cell responses to autoantigens. Human neonatal thymectomy (Tx) results in a decrease in T‐cell numbers and we used this model to study the development of autoreactivity. Two cohorts of neonatally thymectomized individuals were examined, a cohort of young (1–5 years post‐Tx, n = 10–27) and older children (>10 years, n = 26), and compared to healthy age‐matched controls. T‐cell and B‐cell subsets were assessed and autoantibody profiling performed. Early post‐Tx, a decrease in T‐cell numbers (2.75 × 10⁹/L vs. 0.71 × 10⁹/L) and an increased proportion of memory T cells (19.72 vs. 57.43%) were observed. The presence of autoantibodies was correlated with an increased proportion of memory T cells in thymectomized children. No differences were seen in percentages of different B‐cell subsets between the groups. The autoantigen microarray showed a skewed autoantibody response after Tx. In the cohort of older individuals, autoantibodies were present in 62% of the thymectomized children, while they were found in only 33% of the healthy controls. Overall, our data suggest that neonatal Tx skews the autoantibody profile. Preferential expansion and preservation of Treg (regulatory T) cell stability and function, may contribute to preventing autoimmune disease development after Tx.

Association of immunoglobulin G4 and free light chain with idiopathic pleural effusion

The cause of pleural effusion remains uncertain in approximately 15% of patients despite exhaustive evaluation. As recently described immunoglobulin (Ig)G4-related disease is a fibroinflammatory disorder that can affect various organs, including the lungs, we investigate whether idiopathic pleural effusion includes IgG4-associated etiology. Between 2000 and 2012, we collected 830 pleural fluid samples and reviewed 35 patients with pleural effusions undiagnosed after pleural biopsy at Yamaguchi-Ube Medical Center. Importantly, IgG4 immunostaining revealed infiltration of IgG4-positive plasma cells in the pleura of 12 patients (34%, IgG4⁺ group). The median effusion IgG4 level was 41 mg/dl in the IgG4⁺ group and 27 mg/dl in the IgG4^- group (P < 0·01). The light and heavy chains of effusion IgG4 antibodies of patients in the IgG4⁺ group were heterogeneous by two-dimensional electrophoresis, indicating the absence of clonality of the IgG4 antibodies. Interestingly, the κ light chains were more heterogeneous than the λ light chains. The measurement of the κ and λ free light chain (FLC) levels in the pleural fluids showed significantly different κ FLC levels (median: 28·0 versus 9·1 mg/dl, P < 0·01) and κ/λ ratios (median: 2·0 versus 1·2, P < 0·001) between the IgG4⁺ and IgG4^- groups. Furthermore, the κ/λ ratios were correlated with the IgG4⁺ /IgG⁺ plasma cell ratios in the pleura of the IgG4⁺ group. Taken together, these results demonstrate the involvement of IgG4 in certain idiopathic pleural effusions and provide insights into the diagnosis, pathogenesis and therapeutic opportunities of IgG4-associated pleural effusion.

Diagnostic accuracy of salivary and serum-free light chain assays in primary Sjögren's syndrome: a pilot study

OBJECTIVE

To estimate levels of salivary and serum free light chains (FLCs) and explore its utility as a biomarker in primary Sjögren's syndrome (pSS).

METHODS

Patients with pSS classified by American European Consensus group 2002 or American College of Rheumatology 2012 criteria between January 2015 and August 2015 were included. Healthy staff and non-first degree relatives of patients constituted controls. Serum and salivary FLCs were measured by immunoturbidometry using FREELITE^™ Human Kappa(κ) and Lambda(λ) Free Kit (Binding site, Birmingham, UK), on a Roche Modular P800. FLCs were compared between cases and controls using the Mann-Whitney U-test. The receiver operator characteristic curve was constructed to analyze the discriminating ability of salivary and serum kappa and lambda FLCs.

RESULTS

Salivary and serum FLCs were assayed in 15 patients and 13 patients, respectively, and in 15 controls. Median age of cases and controls was 34 years. Salivary kappa and lambda FLCs were higher in pSS as compared to controls (P < 0.05 and P < 0.001, respectively). Serum kappa and lambda FLCs were also higher in pSS (both P < 0.05). Salivary lambda levels were higher in pSS with ocular signs; serum kappa and lambda levels were higher in those with ocular symptoms. A cut off of ≥ 1.1 mg/L for salivary lambda FLC had a sensitivity and specificity of 73.3% and 93.3%, respectively, for the diagnosis of pSS. Serum kappa FLC ≥ 30 mg/L had a sensitivity and specificity of 92.3% and 73.3%, respectively.

CONCLUSION

Serum and salivary FLCs and in particular the latter, are potential biomarkers in pSS. Larger studies are required for validating the findings.

The significance and predictive value of free light chains in the urine of patients with chronic inflammatory rheumatic disease

In patients with rheumatic diseases, reliable markers for determining disease activity are scarce. One potential parameter is the level of immunoglobulin free light chains (FLCs), which is known to be elevated in the blood of patients with certain rheumatic diseases. Few studies have quantified FLCs in urine, a convenient source of test sample, in patients with different rheumatic diseases. We carried out a retrospective analysis of patients with rheumatic disease attending the University hospital of Goettingen, Germany. Subjects were included if they had urine levels of both κ and λ FLCs available and did not have myeloma. Data regarding systemic inflammation and kidney function were recorded, and FLC levels were correlated with inflammatory markers. Of the 382 patients with rheumatic disease, 40.1 % had chronic polyarthritis, 21.2 % connective tissue disease, 18.6 % spondyloarthritis and 15.7 % vasculitis. Elevated levels of κ FLCs were found for 84 % of patients and elevated λ for 52.7 %. For the patients with rheumatoid arthritis, FLCs correlated with C-reactive protein (κ, r = 0.368, p < 0.001; λ, r = 0.398, p < 0.001) and erythrocyte sedimentation rate (κ, r = 0.692, p < 0.001; λ, r = 0.612, p < 0.001). Patients being treated with rituximab displayed FLC levels similar to those of the reference group. There were clear elevations in both κ and λ FLCs in patients with rheumatic disease, but not in κ/λ ratio. The correlation between FLCs and inflammatory markers in patients with rheumatoid arthritis demonstrates their potential for predicting disease activity.

Free light chains: potential biomarker and predictor of mortality in alpha-1-antitrypsin deficiency and usual COPD

Background

Circulating free light chains (FLCs) can alter neutrophil migration, apoptosis and activation and may be a biomarker of autoimmune disease and adaptive immune system activation. These pathogenic roles could be relevant to lung disease in alpha 1 antitrypsin deficiency (A1ATD) and chronic obstructive pulmonary disease (COPD).

Methods

Total combined (c)FLCs were measured using the FreeLite® assay in 547 patients with A1ATD and 327 patients with usual COPD in the stable state, and assessed for association with clinical phenotype, disease severity, airway bacterial colonisation and mortality. Univariate and multivariate analyses were undertaken.

Results

Circulating cFLCs were static in the stable state when measured on 4 occasions in A1ATD and twice in usual COPD. Levels were inversely related to renal function (A1ATD and COPD p = <0.01), and higher in patients with chronic bronchitis (p = 0.019) and airway bacterial colonisation (p = 0.008). After adjusting for renal function and age the relationship between cFLCs and lung function was weak. Kaplan Meier curves showed that cFLC > normal (43.3 mg/L) significantly associated with mortality in both cohorts (A1ATD p = 0.001, COPD p = 0.013).

Conclusions

cFLCs may be a promising biomarker for risk stratification in A1ATD and COPD.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-016-0348-1) contains supplementary material, which is available to authorized users.

Elevated Concentrations of Serum Immunoglobulin Free Light Chains in Systemic Lupus Erythematosus Patients in Relation to Disease Activity, Inflammatory Status, B Cell Activity and Epstein-Barr Virus Antibodies

OBJECTIVE

In this study, we examined the concentration of serum immunoglobulin free light chains (FLCs) in systemic lupus erythematosus (SLE) patients and investigated its association with various disease parameters in order to evaluate the role of FLCs as a potential biomarker in SLE. Furthermore, FLCs' association with Epstein-Barr virus (EBV) antibodies was examined.

METHODS

Using a nephelometric assay, κFLC and λFLC concentrations were quantified in sera from 45 SLE patients and 40 healthy controls. SLE patients with renal insufficiency were excluded in order to preclude high concentrations of serum FLCs due to decreased clearance.

RESULTS

Serum FLC concentrations were significantly elevated in SLE patients compared to healthy controls (p<0.0001) also after adjusting for Ig levels (p<0.0001). The concentration of serum FLCs correlated with a global disease activity (SLE disease activity index (SLEDAI)) score of the SLE patients (r = 0.399, p = 0.007). Furthermore, concentrations of FLCs correlated with titers of dsDNA antibodies (r = 0.383, p = 0.009), and FLC levels and SLEDAI scores correlated in the anti-dsDNA-positive SLE patients, but not in anti-dsDNA-negative SLE patients. Total immunoglobulin (IgG and IgA) concentrations correlated with FLC concentrations and elevated FLC levels were additionally shown to associate with the inflammatory marker C-reactive protein and also with complement consumption determined by low C4 in SLE patients. Collectively, results indicated that elevated serum FLCs reflects increased B cell activity in relation to inflammation. SLE patients had an increased seropositivity of EBV-directed antibodies that did not associate with elevated FLC concentrations. An explanation for this could be that serum FLC concentrations reflect the current EBV activity (reactivation) whereas EBV-directed antibodies reflect the extent of previous infection/reactivations.

CONCLUSION

SLE patients have elevated concentrations of serum FLCs that correlate with global disease activity scores and especially serologic markers for active disease. These findings are suggestive of circulating FLCs having potential as a new supplementary serologic biomarker in SLE.

Distribution of Peripheral Lymphocyte Populations in Primary Sjögren's Syndrome Patients

Purpose of this study was to evaluate the lymphocyte populations' distribution changes in peripheral blood of patients with primary Sjögren's syndrome (pSS). Lymphocyte populations' distribution changes in peripheral blood of pSS patients were investigated in 52 patients with pSS and in 28 healthy controls by flow cytometry. We found decreased absolute count of CD3⁺ T cell population in pSS patients. Analysis of CD4⁺ T cell population showed significant proportion and absolute count differences in pSS patient's blood with SSA/SSB antibodies (Abs) in comparison to controls. No significant differences were observed analyzing CD4⁺ and CD8⁺ Treg subpopulation. Proportion and absolute counts of Th17 cells were significantly lower in pSS patient's blood. Absolute counts of CD8⁺ T cells were significantly lower in pSS patients in comparison to controls and also impaired proportion and absolute counts of CD8⁺ subpopulations according to CD27⁺ and CD57⁺ were observed. Absolute counts of NKT and NK cells were decreased in pSS with Abs. B cells proportion was increased only in blood of pSS with Abs. Lymphocyte distribution impairment can be due to genetically determined lymphopenia or lymphocyte migration from periphery to inflammatory sites or/and increased susceptibility to apoptosis.

Differential effects of cyclophosphamide and mycophenolate mofetil on cellular and serological parameters in patients with systemic lupus erythematosus

INTRODUCTION

Disease activity and therapy show an impact on cellular and serological parameters in patients with systemic lupus erythematosus (SLE). This study was performed to compare the influence of mycophenolate mofetil (MMF) and cyclophosphamide (CYC) therapy on these parameters in patients with flaring, organ-threatening disease.

METHODS

SLE patients currently receiving CYC (n = 20), MMF (n = 25) or no immunosuppressive drugs (n = 22) were compared using a cross-sectional design. Median disease activity and daily corticosteroid dose were similar in these treatment groups. Concurrent medication, organ manifestations, and disease activity were recorded, and cellular and serological parameters were determined by routine diagnostic tests or flow cytometric analysis. In addition follow-up data were obtained from different sets of patients (CYC n = 24; MMF n = 23).

RESULTS

Although both drugs showed a significant effect on disease activity and circulating B cell subsets, only MMF reduced circulating plasmablasts and plasma cells as well as circulating free light chains within three months of induction therapy. Neither MMF nor CYC were able to reduce circulating memory B cells. MMF lowered IgA levels more markedly than CYC. We did not observe a significant difference in the reduction of IgG levels or anti-dsDNA antibodies comparing patients receiving MMF or CYC. In contrast to MMF, induction therapy with CYC was associated with a significant increase of circulating CD8+ effector T cells and plasmacytoid dendritic cells (PDCs) after three months.

CONCLUSIONS

The results indicate differences between MMF and CYC with regard to the mechanism of action. MMF, but not CYC, treatment leads to a fast and enduring reduction of surrogate markers of B cell activation, such as circulating plasmablasts, plasma cells and free light chains but a comparable rate of hypogammaglobulinemia.

Association of serum TNF-α, IL-8 and free light chain with HLA-DR B alleles expression in pulmonary and extra-pulmonary sarcoidosis

Background

Sarcoidosis is a systemic disease of unknown etiology characterized histologically by the observation of non-caseating granulomas and several immunological abnormalities. Sarcoidosis is a multi-organ disorder which involves formation of granulomas in many tissues including the lungs (pulmonary) and others such as skin, bone, heart (extra pulmonary). Associations between human leukocyte antigens (HLA), the encoded cell surface receptor (HLA-DR) and sarcoidosis have been reported in several studies. Several HLA-DR alleles have been described as potential risk factors for sarcoidosis in distinct ethnic groups however evidence for a relationship between HLA-DR alleles and pulmonary and extra-pulmonary sarcoidosis (EPS) is still scarce. Although the etiology of the disease remains unclear, infectious and environmental factors have been postulated. Inflammatory cytokines and chemokines may play important roles in the pathogenesis of sarcoidosis and serum free light chain (FLC) numbers have been implicated in several immunologic disorders.

Purpose of the study

The aim of the present study was to investigate HLA associations with serum cytokines and FLC in Iranian patients with pulmonary (n = 86) and EPS (n = 46).

Results

We found that among the 16 HLA DRB alleles only *7 and *12 were different in sarcoidosis patients. The levels of TNF-α and IL-8 in pulmonary sarcoidosis patients were higher than in EPS (P < 0.05) whereas the levels of FLC subunits in EPS were higher than in pulmonary sarcoidosis.

Conclusion

This data may suggests a link between HLA-DRB *12 and sarcoidosis in Iranian population.

Free Light Chains in patients with acute coronary syndromes: Relationships to inflammation and renal function

AIMS

We assessed changes of serum combined free immunoglobulin light chains (cFLC) levels, which are associated with increased all-cause mortality, in ST-elevation myocardial infarction (STEMI) in relation to inflammation and renal function indices.

METHODS

cFLC were measured in 48 patients with STEMI on days 1, 3, 7 and 30 with assessment of their relationships with monocyte subsets, high sensitivity C-reactive protein (hsCRP), and cystatin C. Day 1 levels in STEMI patients were compared to 40 patients with stable coronary artery disease, and 37 healthy controls.

RESULTS

There were no significant differences in cFLC levels between the study groups. In STEMI patients, cFLC values peaked on day 7 post-MI and remained elevated on day 30 (p<0.001 vs. day 1 for both). hsCRP concentrations peaked on day 3 of STEMI followed by their gradual reduction to the levels seen in the controls (p<0.001). In STEMI cFLC correlated with cystatin C (r=0.55, p<0.001), and negatively correlated with counts of CD14++CD16- monocytes (r=-0.55, p<0.001). On multivariate Cox regression analysis, cFLC concentrations were associated with increased need for future percutaneous coronary intervention (PCI) (p=0.019).

CONCLUSION

cFLC levels increase during STEMI with peak values on day 7 after presentation and predict the need for future PCI.

Elevation of serum immunoglobulin free light chains during the preclinical period of rheumatoid arthritis

OBJECTIVE

Immunoglobulin free light chains (FLC) represent biomarkers of B cell activity in rheumatoid arthritis (RA) and are associated with all-cause mortality in the general population. Our objective was to evaluate the relationships of serum FLC to preclinical disease, RA characteristics, and mortality in RA compared to non-RA subjects.

METHODS

A population-based study in Olmsted County, Minnesota, USA, was performed by crosslinking a large cohort in the general population having available serum FLC measurements with established RA incidence and prevalence cohorts. Serum κ, λ, and total FLC and their trends relative to RA incidence were compared between RA and non-RA subjects. Regression models were used to determine the associations between FLC, disease characteristics, and mortality, testing for differential effects of FLC on mortality in RA.

RESULTS

Among 16,609 subjects, 270 fulfilled the criteria for RA at the time of FLC measurement. Mean total FLC were significantly higher in RA compared to non-RA subjects (4.2 vs 3.3 mg/dl, p < 0.001). FLC became elevated 3-5 years before the clinical onset of RA and remained elevated during followup. Polyclonal FLC were found to predict higher mortality in persons with RA, though elevation to the highest decile had a relatively lower effect on mortality in RA compared to non-RA subjects.

CONCLUSION

Elevation of serum FLC precedes the development of RA and may be useful in monitoring B cell activity and disease progression. FLC are associated with mortality among patients with RA as well as the general population.

Immune Activation: Contribution to AIDS-Associated Non-Hodgkin Lymphoma

HIV infection is associated with a greatly elevated risk for the development of non-Hodgkin lymphoma (NHL), which while diminished, remains elevated in the highly active antiretroviral therapy (HAART) era. Chronic B cell activation, driven by contact with HIV virions, B cell-stimulatory cytokines, viruses (EBV, HPV, HCV), and by high levels of antigenic stimulation occurs in HIV infected persons, and it is seen at even higher levels in those who go on to develop AIDS-NHL. Evidence from multiple studies indicates that elevated serum levels of several B cell-stimulatory cytokines and biomarkers are seen preceding AIDS-NHL, as well as in immunocompetent persons that develop NHL. Phenotypic changes in circulating B cells also are seen preceding AIDS-NHL, including the expression of AICDA, and of cell-surface molecules and miRNA that are associated with activated B cells. HAART only partially normalizes the immune system of treated HIV⁺ persons as they still show clear evidence for ongoing inflammation and immune activation in, even those who show complete suppression of HIV viremia. Together, this provides ample evidence to support the notion that chronic activation of B cells contributes to the genesis of B cell lymphomas.

Free light chains in patients with acute heart failure secondary to atherosclerotic coronary artery disease

Increased combined free light chains (cFLCs) are strongly prognostic of death in general populations and in patients with chronic kidney disease, but scarce data are available on cFLC in heart failure (HF). The aim of this study was to assess the dynamics and prognostic significance of cFLC levels in patients after admission with acute HF (AHF). cFLC measurements were compared in 49 patients with AHF, 37 patients with stable HF, 43 patients with stable coronary artery disease and without HF ("disease controls"), and 37 healthy controls. The association of cFLC with death and/or rehospitalization was assessed. Patients with AHF had significantly elevated cFLC levels, compared with other groups (p <0.001). Patients with stable HF showed higher levels of cFLCs than healthy controls. In patients with AHF, cFLC levels were correlated with cystatin C (Spearman's r = 0.63, p <0.001) and creatinine (Spearman's r = 0.47, p = 0.002). During 3-month follow-up, brain natriuretic peptide was reduced significantly (p = 0.017), but cFLCs did not change significantly. In a multivariate Cox regression analysis, the higher quartiles of cFLCs were significantly associated with death or readmission (hazard ratio 8.34, 95% confidence interval 2.38 to 29.22, p = 0.0009) after adjustment for age, gender, brain natriuretic peptide and cystatin C levels. Higher quartiles of cFLCs were prognostic for death alone (hazard ratio 14.0, 95% confidence interval 1.72 to 113.8, p = 0.014). In conclusion, increased serum cFLC concentrations in patients with AHF were independently associated with prognosis. In patients with AHF, elevated cFLC levels persist long after clinical stabilization, which may reflect immune disturbances and/or the reduced capacity of (perhaps functionally impaired) kidneys and the endothelium to eliminate them.