Free Immunoglobulin Light Chains as a Risk Factor in Renal and Extrarenal Complications

COVID-19 Vaccination in Kidney Transplant Candidates and Recipients

Kidney transplant candidates and kidney transplant recipients (KTRs) are at particular risk of severe complications of COVID-19 disease. In Western countries, mortality in affected hospitalized KTRs ranges between 19% and 50%. COVID-19 vaccination remains the most important measure to prevent the severity of infection in candidates and recipients of kidney transplant. However, the uraemic condition may affect the vaccine-induced immunity in patients with advanced chronic kidney disease (CKD) and in KTRs. Retention of uraemic toxins, dysbiosis, dysmetabolism, and dialysis can diminish the normal response to vaccination, leading to dysfunction of inflammatory and immune cells. In KTRs the efficacy of vaccines may be reduced by the immunosuppressive medications, and more than half of kidney transplant recipients are unable to build an immune response even after four administrations of anti-COVID-19 vaccines. The lack of antibody response leaves these patients at high risk for SARS-CoV-2 infection and severe COVID-19 disease. The aim of the present review is to focus on the main reasons for the impaired immunological response among candidates and kidney transplant recipients and to highlight some of the present options available to solve the problem.

Anti-BCMA CAR-T Cell Therapy in Relapsed or Refractory Multiple Myeloma Patients with Impaired Renal Function

Anti-B cell maturation antigen (BCMA) chimeric antigen receptor (CAR) T-cell therapy is effective and well-tolerated for refractory or relapsed multiple myeloma (RRMM). The purpose of the present study was to analyze efficacy in RRMM patients with renal impairment treated by anti-BCMA CAR-T cell therapy. A total of 59 RRMM patients were selected, and divided into impaired renal function (IRF) group [baseline estimated glomerular filtration rate (eGFR) < 90 mL/min/1.73 m² (n=18)] and normal renal function (NRF) group (baseline eGFR ≥ 90 mL/min/1.73 m², n=41). For patients with IRF, eGFR at the 6th month post-CAR-T cells infusion was significantly higher than the baseline (P<0.05). The multivariate analysis showed that light chain type and beta-2 micro-globulin (beta-2M) were associated factors with the decrease of serum creatinine. Median progression-free survival (PFS) in the NRF group and IRF group was 266 days and 181 days respectively. Overall survival (OS) in the NRF group and IRF group was 877 days and 238 days respectively. There was no significant difference in the objective response rate (ORR) between the IRF group and the NRF group. It is suggested that CAR-T cells therapy could improve the renal function during the treatment of RRMM. The renal function could be more significantly improved in RRMM patients with light chain type than with other types.

Alteration of the Gut Microbiome in Chronic Kidney Disease Patients and Its Association With Serum Free Immunoglobulin Light Chains

Objectives

Gut dysbiosis is associated with chronic kidney disease (CKD), and serum free immunoglobulin light chains (FLCs) are biomarkers for CKD. This study aims to assess the CKD gut microbiome and to determine its impact on serum FLC levels.

Methods

To control for confounders, 100 patients and sex- and age-matched healthy controls (HCs) were recruited. The gut microbiome was assessed by sequencing 16S rRNA gene V3-V4 hypervariable regions. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States was applied to infer functional metabolic pathways. When observing group differences in the microbiome and predicted metabolic pathways, demographic confounders were adjusted using binary logistic regression; when examining impacts of the gut microbiome and metabolic pathways on serum FLCs, factors influencing FLC levels were adjusted using multiple regression.

Results

Principal coordinate analysis revealed a significantly different bacterial community between the CKD and HC groups (P < 0.05). After adjusting for confounders, lower Chao 1, observed species and Shannon indices based on binary logistic regression predicted CKD prevalence. Actinobacteria, Alistipes, Bifidobacterium and Bifidobacterium longum enrichment, upregulation of metabolic pathways of bacterial toxin, chloroalkane and chloroalkene degradation, and Staphylococcus aureus infection also predicted CKD prevalence (P < 0.05). Furthermore, depletion of Actinobacteria and Bifidobacterium and reduced chloroalkane and chloroalkene degradation predicted high levels of FLC λ (P < 0.05).

Conclusions

Gut dysbiosis in CKD patients was confirmed by controlling for confounders in the present study. Additionally, the association between gut dysbiosis and FLC λ levels demonstrates the existence of crosstalk between the microbiome and immune response in CKD.

The Association of Serum Free Light Chains With Mortality and Progression to End-Stage Renal Disease in Chronic Kidney Disease: Systematic Review and Individual Patient Data Meta-analysis

OBJECTIVE

To clarify the associations between polyclonal serum free light chain (sFLC) levels and adverse outcomes in patients with chronic kidney disease (CKD) by conducting a systematic review and individual patient data meta-analyses.

PATIENTS AND METHODS

On December 28, 2016, we searched 4 databases (MEDLINE, Embase, CINAHL, and PubMed) and conference proceedings for studies presenting independent analyses of associations between sFLC levels and mortality or progression to end-stage renal disease (ESRD) in patients with CKD. Study quality was assessed in 5 domains: sample selection, measurement, attrition, reporting, and funding.

RESULTS

Five prospective cohort studies were included, judged moderate to good quality, involving 3912 participants in total. In multivariable meta-analyses, sFLC (kappa+lambda) levels were independently associated with mortality (5 studies, 3680 participants; hazard ratio [HR], 1.04 [95% CI, 1.03-1.06] per 10 mg/L increase in sFLC levels) and progression to ESRD (3 studies, 1848 participants; HR, 1.01 [95% CI, 1.00-1.03] per 10 mg/L increase in sFLC levels). The sFLC values above the upper limit of normal (43.3 mg/L) were independently associated with mortality (HR, 1.45 [95% CI, 1.14-1.85]) and ESRD (HR, 3.25 [95% CI, 1.32-7.99]).

CONCLUSION

Higher levels of sFLCs are independently associated with higher risk of mortality and ESRD in patients with CKD. Future work is needed to explore the biological role of sFLCs in adverse outcomes in CKD, and their use in risk stratification.

Performance of hemodialysis with novel medium cut-off dialyzers

Background. Compared to high-flux dialysis membranes, novel medium cut-off (MCO) membranes show greater permeability for larger middle molecules.

Methods. In two prospective, open-label, controlled, randomized, crossover pilot studies, 39 prevalent hemodialysis (HD) patients were studied in four dialysis treatments as follows: study 1, three MCO prototype dialyzers (AA, BB and CC with increasing permeability) and one high-flux dialyzer in HD; and study 2, two MCO prototype dialyzers (AA and BB) in HD and high-flux dialyzers in HD and hemodiafiltration (HDF). Primary outcome was lambda free light chain (λFLC) overall clearance. Secondary outcomes included overall clearances and pre-to-post-reduction ratios of middle and small molecules, and safety of MCO HD treatments.

Results. MCO HD provided greater λFLC overall clearance [least square mean (standard error)] as follows: study 1: MCO AA 8.5 (0.54), MCO BB 11.3 (0.51), MCO CC 15.0 (0.53) versus high-flux HD 3.6 (0.51) mL/min; study 2: MCO AA 10.0 (0.58), MCO BB 12.5 (0.57) versus high-flux HD 4.4 (0.57) and HDF 6.2 (0.58) mL/min. Differences between MCO and high-flux dialyzers were consistently significant in mixed model analysis (each P < 0.001). Reduction ratios of λFLC were greater for MCO. Clearances of α1-microglobulin, complement factor D, kappa FLC (κFLC) and myoglobin were generally greater with MCO than with high-flux HD and similar to or greater than clearances with HDF. Albumin loss was moderate with MCO, but greater than with high-flux HD and HDF.

Conclusions. MCO HD removes a wide range of middle molecules more effectively than high-flux HD and even exceeds the performance of high-volume HDF for large solutes, particularly λFLC.

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.

Optimizing the treatment of patients with multiple myeloma and renal impairment

Renal impairment is a common complication of multiple myeloma. It is found in about 20% to 25% of patients at diagnosis and in ≤ 50% at some point during the disease course. The presence of renal insufficiency diminishes patients' quality of life and has been associated with increased mortality, although the outcomes of patients after successful induction therapy have been comparable to those with normal renal function. Therefore, the treatment of patients with multiple myeloma and renal impairment is a major challenge and should aim to achieve remission in a large proportion of patients. New drugs introduced to treat multiple myeloma during the past decade have an established place in the treatment of patients with renal failure. Bortezomib appears to be most beneficial in this setting and, combined with other drugs, provides a chance for rapid remission and related improvement of renal function. Immunomodulatory drugs such as thalidomide and lenalidomide have also been used successfully in patients with renal insufficiency, although for the latter drug appropriate dose adjustments are necessary. The presence of renal failure is not a contraindication to autologous bone marrow transplantation in patients eligible for this procedure. Among the classic cytotoxic agents, bendamustine, in particular, should be considered for patients with renal insufficiency. Appropriate supportive care is also extremely important in the treatment of patients with multiple myeloma and renal failure. It can include plasmapheresis and removal of free light chains with high cut-off hemodialysis, adapted dosages of bisphosphonates, and avoidance of drugs and conditions that can impair renal function.

Elevated serum free light chains predict cardiovascular events in type 2 diabetes

OBJECTIVE

Elevated polyclonal serum immunoglobulin free light chains (FLCs; combined FLCκ+FLCλ [cFLC]) are associated with adverse clinical outcomes and increased mortality; we investigated cFLC and cardiovascular disease (CVD) events in type 2 diabetes.

RESEARCH DESIGN AND METHODS

In a cohort study of 352 south Asian patients with type 2 diabetes, serum cFLC, high-sensitivity C-reactive protein (hsCRP), and standard biochemistry were measured. CVD events over 2 years were recorded and assessed using multiple logistic regression.

RESULTS

cFLC levels were elevated significantly in 29 of 352 (8%) patients with CVD events during 2 years of follow-up (50.7 vs. 42.8 mg/L; P = 0.004). In multivariate analysis, elevated cFLC (>57.2 mg/L) was associated with CVD outcomes (odds ratio 3.3 [95% CI 1.3-8.2]; P = 0.012) and remained significant after adjusting for age, albumin-to-creatinine ratio, diabetes duration, or treatment.

CONCLUSIONS

cFLC elevation is a novel marker for CVD outcomes in type 2 diabetes that warrants further investigation.

Association between the delta estimated glomerular filtration rate and the prevalence of monoclonal gammopathy of undetermined significance in Korean males

Background. We investigated the association between the reduction in the estimated glomerular filtration rate (eGFR) and the prevalence of monoclonal gammopathy of undetermined significance (MGUS) in Korean males. Methods. We enrolled 723 healthy Korean males. Serum creatinine concentration, serum electrophoresis, serum immunofixation, and the serum free light chain assay were performed. We calculated delta eGFR per year (ΔeGFR/yr). The prevalence of MGUS was compared based on the ΔeGFR/yr and age group. Results. Thirteen (1.8%) of 723 participants exhibited the monoclonal band on serum immunofixation. Prevalence of MGUS by age group was 0.00% (0/172 for 40 years), 1.63% (6/367 for 60 years), and 3.80% (7/184 for >60 years). The median decrease in ΔeGFR/yr was 5.3%. The prevalence of MGUS in participants in their 50s with >5.3% decline in ΔeGFR/yr was significantly higher than those with <5.3% decrease in ΔeGFR/yr (3.16% versus 0.00%; P = 0.049). The prevalence of MGUS in participants in their 50s with >5.3% decrease in ΔeGFR/yr was similar to that of healthy males in their 60s. Conclusion. Using the rate of reduction in ΔeGFR/yr in healthy Korean males who had their serum creatinine level checked regularly may increase the MGUS detection rate in clinical practice.

Serum polyclonal immunoglobulin free light chain levels predict mortality in people with chronic kidney disease

OBJECTIVE

To determine whether elevated serum polyclonal free light chain (FLC) levels predict mortality in a population of individuals with chronic kidney disease (CKD).

PATIENTS AND METHODS

From January 2, 2006, through July 31, 2007, we recruited a cohort of 848 people with CKD who were not receiving renal replacement therapy and did not have monoclonal gammopathy. We measured serum kappa FLC and lambda FLC isotype levels to determine combined FLC (cFLC) levels. The cohort was prospectively followed up for a median of 63 months (interquartile range, 0-93 months). Cox regression analysis was performed to determine variables predictive of mortality.

RESULTS

High cFLC levels were an independent risk factor for death (hazard ratio [HR], 2.71; 95% CI, 1.98-3.70; P<.001). Other independent risk factors were age (HR, 1.79; 95% CI, 1.52-2.10; P<.001), South Asian ethnicity (HR, 0.33; 95% CI, 0.14-0.64; P=.02), preexisting cardiovascular disease (HR, 1.59; 95% CI, 1.09-2.31; P=.02), and high-sensitivity C-reactive protein (HR, 1.13; 95% CI, 1.00-1.28; P=.04). Neither estimated glomerular filtration rate nor albuminuria was an independent risk factor for death.

CONCLUSION

High cFLC levels independently predict mortality in people with CKD.

Comparison between on-line high-efficiency hemodiafiltration and conventional high-flux hemodialysis for polyclonal free light chain removal

BACKGROUND

Polyclonal free light chains (FLC) are considered as middle molecular weight uremic toxins in chronic kidney disease. In this study, we investigate polyclonal FLC removal by comparing conventional high-flux hemodialysis (HD) and online high-efficiency hemodiafiltration (ol-HDF) in end-stage renal disease patients.

METHODS

We analyzed 31 chronic dialysis patients who were treated by HD then by postdilution ol-HDF during a prospective study. All patients were anuric and without monoclonal gammopathy. Serum pre- and postdialysis FLC were collected during 4 sessions: 1 HD session and 3 ol-HDF sessions. We calculated the reduction ratio using kinetic modeling.

RESULTS

The κ reduction ratio was higher with ol-HDF than with HD (66 ± 14 vs. 52 ± 13%, p < 0.001). However, the λ reduction ratio was not significantly higher with ol-HDF (37 ± 20 vs. 37 ± 15%, p = 0.67). Furthermore, predialysis κ- and λ-FLC increased with ol-HDF compared with HD (κ 155 ± 82 vs. 87 ± 47 mg/l, p < 0.05; λ 101 ± 46 vs. 72 ± 41 mg/l, p < 0.05). Postdialysis FLC levels were raised only for λ-FLC with ol-HDF (74 ± 39 vs. 53 ± 31 mg/l, p < 0.05) and were not significantly different for κ.

CONCLUSIONS

This study shows that κ-FLC removal is better in ol-HDF compared with HD, whereas there is no difference in λ-FLC removal. Surprisingly, predialysis κ and λ levels are both increased in ol-HDF, which is disturbing since polyclonal excess of λ-FLC is associated with mortality in chronic kidney disease.

Association of urinary laminin G-like 3 and free K light chains with disease activity and histological injury in IgA nephropathy

BACKGROUND AND OBJECTIVES

IgA nephropathy has variable clinical presentation and progression. Its definitive diagnosis and prognosis require renal biopsy. The identification of new biomarkers allowing noninvasive diagnosis and monitoring of disease activity would be advantageous. This study analyzed the urine proteome of IgA nephropathy patients at an early stage of disease.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Urine from 49 IgA nephropathy patients, 42 CKD patients, and 40 healthy individuals was analyzed by surface-enhanced laser desorption/ionization time of flight/mass spectrometry. Differentially excreted proteins were identified by matrix-enhanced laser desorption/ionization time of flight/mass spectrometry, confirmed by immunologic methods, and validated in an independent set of patients (14 IgA nephropathy and 24 CKD). All patients were recruited at the Division of Nephrology of the University of Foggia from January of 2005 to March of 2007.

RESULTS

Two proteins, with 21,598 and 23,458 m/z, were significantly decreased in IgA nephropathy and identified as Perlecan laminin G-like 3 peptide and Ig κ light chains, respectively. Western blot analysis confirmed the lower urinary excretion of laminin G-like 3 in IgA nephropathy patients compared with CKD patients and healthy individuals. Immunonephelometry analysis confirmed the lower urinary excretion of free κ light chains in IgA nephropathy patients compared with CKD patients and healthy individuals. Immunohistochemistry analysis justified the urinary excretion profile of such proteins in IgA nephropathy. Finally, urinary free κ light chains and laminin G-like 3 concentration inversely correlated with severity of clinical and histologic features of our IgA nephropathy cohort.

CONCLUSIONS

Laminin G-like 3 and free κ light chains can contribute to the noninvasive assessment of IgA nephropathy disease activity.

Proteomic analysis of plasma after branched chain enriched mixture supplementation in mice

Background

Branched chain amino acid (BCAA) supplementation is a recently identified strategy to promote longevity in mice. A proteomic approach was used to identify proteins which are differentially expressed in the sera of mice following supplementation with selected branched chain amino acid enriched mixture (BCAAem).

Findings

12 male mice (C57Bl6, 9 months-old) were randomly assigned to unsupplemented (Control, n = 6) and supplemented (BCAA, n = 6, 0.1 mg/gr/day in drink water for 4 weeks). At the end of treatment total plasma samples from Control and BCAAem mice were separated by two-dimensional gel electrophoresis (2-DE). After staining, the gels were imaged and differential protein expression patterns were interrogated using image analysis software. Spots showing a different expression level were identified through a comparison with 2D maps found in databases officially recognized (ExPASy).

Master gels of Control and BCAA mice exhibited slightly different 2-DE patterns as only 10 spots out of 500 appeared differentially expressed: 8 were upregulated (corresponding to Apolipoprotein A-I (APOA1), Complement factor B, Complement C3, Immunoglobulin light chain) and 2 appeared downregulated (Alpha-1-antitrypsin and unknown).

Conclusions

Supplementation with BCAAem in mice results in a slight perturbation of the host serum proteome. Of particular interest is the increased Apolipoprotein A-I (APOAI) following treatment.

Management of myeloma-associated renal dysfunction in the era of novel therapies

Multiple myeloma (MM) is a plasma cell neoplasm often associated with renal impairment (RI), with myeloma cast nephropathy recognized as the most common cause. While RI is present in over 50% of MM patients at some point in their disease course, it is associated with higher tumor burden, more aggressive disease, diminished quality of life, development of complications and increased mortality. The introduction of novel therapies, including bortezomib, lenalidomide and thalidomide, has revolutionized the management of MM. They are now considered first-line therapies in induction, maintenance and salvage therapy for MM. In addition to their anti-MM effect, they can improve outcome in patients with RI, especially when combined, and bortezomib with dexamethasone may have a renal protective effect. This review focuses on the use of these agents in patients with MM and RI, and evaluates their efficacy, safety, need for dose adjustment and impact on RI.

Multiple myeloma

Multiple myeloma (MM) is a B cell neoplasm of the bone marrow with a complex array of clinical manifestations including anemia, bone lesions, hypercalcemia, renal dysfunction, and compromised immune function. It accounts for 10%-15% of all hematologic malignancies, and 20% of deaths related to cancers of the blood and bone marrow. The diagnosis of MM is based on the presence of neoplastic plasma cells in the bone marrow or other extramedullary sites, along with evidence of disease-related organ dysfunction. Although the disease remains incurable, significant advances in both basic and translational research have enhanced understanding of disease pathogenesis and guided the development of new and more effective therapies. These agents include the immunomodulatory drugs thalidomide and lenalidomide, the proteasome inhibitor bortezomib, and other therapeutics that are currently being evaluated. This review highlights important historical landmarks in the field of MM, examines the pathogenesis and clinical manifestations of the disease, and outlines principles of both diagnosis and treatment of MM.

Quantitative assessment of serum free light chains in renal transplantation

Plasma cell dyscrasias can cause renal disease. Sensitive methods have recently been introduced to quantify serum free light chains (sFLCs). Renal function may influence the variability of these methods, as shown in chronic kidney disease (CKD) patients, but this problem has not been widely addressed in renal transplant patients. Herein, we examined the association between polyclonal sFLC concentrations and renal function among a population of renal transplant patients. We studied 102 kidney allograft recipients and 53 CKD patients classified according to KDOQI (Kidney Disease Outcomes Quality Initiative) stages. None of them had been diagnosed with monoclonal gammopathy. sFLCs were quantified by nephelometry. Both serum κ and λ free light chain concentrations rose progressively through each stage of KDOQI among both transplant and nontransplant patients (P<.0001). In the former setting, sFLC concentrations significantly correlated, using a Spearman coefficient, with serum creatinine, and serum cystatin concentrations as well as estimated glomerular filtration rate: namely, 0.723, 0.797, and -0.711 for sκFLC and 0.705, 0.759, and -0.694 for sλFLC, respectively (P<.0001 in all cases). Spearman correlation coefficients in nontransplant patients were: 0.559, 0.848, and -0.766 for sκFLC and 0.702, 0.875, and -0.855 for sλFLC, respectively (P<.0001 in all cases). In conclusion, sFLCs must be interpreted cautiously due to their clear association with renal function. Therefore, renal transplantation did not produce changes that were different from those dependent on renal function.

Platelet/Leukocyte activation, inflammation, and uremia

Chronic kidney disease (CKD) is a state of chronic, low-grade inflammation which contributes to the accelerated progression of chronic inflammatory disturbances of which atherosclerosis is a major example. Platelet and leukocyte activation and interaction, evoked by the uremic condition, play an important role in this process. The effect of specific uremic retention solutes, progressively retained in uremia, on important platelet and leukocytes functions is discussed and summarized. The main uremic toxins involved are molecules with a molecular weight above 500 Da (the so-called "middle molecules") and/or protein-bound molecules. Classification of the molecules and elucidation of the pathophysiological pathways involved will result in new therapeutic strategies pursuing specific removal or pharmacological neutralization of molecular impact.