AL(light chain)-amyloidogenesis by mesangial cells involves active participation of lysosomes: An ultrastructural study

Amyloid formation by cells is a stepwise process that occurs in macrophages and cells capable of transforming into a macrophage phenotype. One such cell is the mesangial cell in the kidney. It has been shown that mesangial cells are engaged in AL (light chain associated)- amyloidogenesis after transforming phenotypically from a smooth muscle to a macrophage phenotype. The actual process of amyloid fibril formation has not been dissected. This ultrastructural study which includes the examination of lysosomal gradient specimens addresses this issue by analyzing the sequence of events that takes place as fibrils are formed in endosomes and lysosomes. The findings indicate that fibrillogenesis begins in endosomes but is completed and most pronounced in the lysosomal compartment. As early as 10 min after incubation of human mesangial cells with AL-LCs, amyloid fibrils are formed in endosomes but mostly occurs in the mature lysosomal compartment. This is the first time that fibril formation is demonstrated experimentally occurring inside human mesangial cells and the entire sequence of events taking place is elucidated.

The order of immunoglobulin light chain κ and λ usage in primary and secondary lymphoid tissues of germ-free and conventional piglets

In pigs (Sus scrofa), the initial immunoglobulin rearrangement of the κ light chain is replaced by λ before the heavy chains rearrange, and the light chains may rearrange even later. This study investigates whether these developmental differences are reflected in the usage of IGK and IGL genes. We found large differences between peripheral B cells and those developing in the bone marrow, and between B cells in germ-free piglets and conventional pigs. During early B cell development in the bone marrow, more 3' V and 5' J gene segments for both light chains are used. However, in the peripheral naive repertoire, more 5' IGLV and 3' IGLJ genes are used. A similar shift toward the use of more 5' IGKV and 3' IGKJ genes is observed later after antigen exposure in conventional pigs. The expression profile showed that most λ⁺ B cells are generated earlier, while κ⁺ B cells develop from late precursors that already contain the λ rearrangement. The initial λ rearrangement is retained in both λ⁺ and κ⁺ B lymphocytes, and multiple λ transcripts can be found in individual cells. The overall pool of the IGLV repertoire is therefore much larger and more diversified than for IGKV. The κ repertoire is further restricted to the preferential use of only two major IGKV genes, reflecting the limitation for only two consecutive rearrangements. Tracing of silenced λ transcripts in κ⁺ B cells further confirmed the unconventional mechanism of differential rearrangements in pigs. Our results underline the diversity of the immune system among mammals.

Imaging-Guided Treatment for Cardiac Amyloidosis

Purpose of Review

This review will explore the role of cardiac imaging in guiding treatment in the two most commonly encountered subtypes of cardiac amyloidosis (immunoglobulin light-chain amyloidosis [AL] and transthyretin amyloidosis [ATTR]).

Recent Findings

Advances in multi-parametric cardiac imaging involving a combination of bone scintigraphy, echocardiography and cardiac magnetic resonance imaging have resulted in earlier diagnosis and initiation of treatment, while the evolution of techniques such as longitudinal strain and extracellular volume quantification allow clinicians to track individuals’ response to treatment. Imaging developments have led to a deeper understanding of the disease process and treatment mechanisms, which in combination result in improved patient outcomes.

Summary

The rapidly expanding treatment regimens for cardiac amyloidosis have led to an even greater reliance on cardiac imaging to help establish an accurate diagnosis, monitor treatment response and aid the adjustment of treatment strategies accordingly.

Potential Cardiac Amyloid PET/CT Imaging Targets for Differentiating Immunoglobulin Light Chain From Transthyretin Amyloidosis

PURPOSE OF THE REVIEW

Cardiac involvement in amyloidosis plays a critical role in the clinical manifestation and prognostication. Since advanced treatment options for immunoglobulin light chains (AL) or liver-generated protein transthyretin (TTR) are quite different, a non-invasive and comprehensive imaging approach for the identification and characterization of these forms of cardiac amyloidosis is warranted.

RECENT FINDINGS

Various ¹⁸Flabeled radiotracers and positron emission tomography (PET) imaging have been appreciated as a as a valid and non-invasive diagnostic approach to identify and quantify disease activity of cardiac amyloidosis. Interestingly, applying ¹⁸F-florbetapen and delayed PET imaging may even afford the possibility to not only detect cardiac amyloidosis but also to reliably differentiate between AL and TTR, respectively. This review summarizes contributions of cardiac PET imaging for the non-invasive identification and potential differentiation between AL and TTR amyloidosis that likely holds promise to gear medical treatment in the individual patient for an improved outcome.

Genomic architecture and repertoire of the rainbow trout immunoglobulin light chain genes

The genomic loci encoding the four immunoglobulin light chains (IgL1, IgL2, IgL3, and IgL4) in the Swanson trout genome assembly were annotated in order to provide a measurement of the potential IgL repertoire. IgL1 and IgL3 gene segments are co-localized on chromosomes 21, 18, 15, and 7 while IgL2 and IgL4 were found on chromosomes 13 and 17, respectively. In total, 48 constant (C_L), 87 variable (V_L), and 59 joining (J_L) productive genes are described. Pairwise alignment of the V_L segments revealed that they belong to nine different families, three of which (kappa IV, V, and VI) are described for the first time in this study. V_L and C_L sequences on chromosome 15 and 21 and those on chromosomes 7 and 18 clustered together in phylogenetic analysis. PCR was used to examine IgL C_L and V_L genes in 9 lines of rainbow trout. IgL4 in the Hot Creek and Golden trout lines was missing 42 nucleotides resulting in a loss of 14 amino acids. The sigma IV variable family was completely absent from the Swanson, Arlee, Hot Creek, and wild type lines and silenced in the Skamania line with the addition of 176 bp mini-satellite insert. Similarly, the Whale Rock, Arlee, and wild type lines were all found to encode two sigma II products, a functional 252 bp product and a larger 425 bp product that contained a 172 bp insert. Results from this study indicate that there are genomic differences in IgL repertoire between different lines of trout that could affect humoral immune responses post vaccination and during disease.

Clinicopathological characteristics of light chain proximal tubulopathy in Korean patients and the diagnostic usefulness of immunohistochemical staining for immunoglobulin light chain

BACKGROUND

Light chain proximal tubulopathy (LCPT) is a rare paraproteinemic renal disease that has been mostly reported in Western patients. LCPT is characterized by the accumulation of immunoglobulin (Ig)-light chain (LC) in the proximal tubule. Immunohistochemical staining for Ig-LC has not been investigated in the context of LCPT. We reported the clinicopathological characteristics and Ig-LC immunoexpression of patients with LCPT for the first time in Korea.

METHODS

We reviewed the clinicopathological findings of 5 Korean patients diagnosed with LCPT between 2016 and 2018. In addition, immunohistochemical staining for κ-LC and λ-LC was conducted on paraffin-embedded tissues.

RESULTS

The median age was 63 years, and the male-to-female ratio was 3:2. The primary renal manifestations were either azotemia or tubular proteinuria. All patients were diagnosed with multiple myeloma with monoclonal κ-LC (#1-2) or λ-LC (#3-5) in the serum and urine. Kidney biopsies revealed diverse and subtle alterations of the proximal tubule, including crystallization, vacuolization, and/or swelling. Electron microscopy revealed crystals in patients #1-2 and non-crystalline particles within numerous/large/dysmorphic lysosomes in patients #3-5. Ig-LC restriction was demonstrated in the proximal tubule as κ-type in patients #1-2 and as λ-type in patients #3-5 by immunohistochemistry and immunofluorescence. Immunohistochemical staining showed diffuse positivity to κ- and λ-LC, although immunofluorescent staining for κ-LC was focal and weak. LCPT has diverse clinicopathological characteristics and subtle morphological alterations, which necessitate ancillary tests for diagnosis.

CONCLUSIONS

We introduced immunohistochemical staining for Ig-LC as a useful tool for the diagnosis of LCPT, especially in the case of κ-type crystals.

Characterization of immunoglobulin light chain utilization and variable family diversity in rainbow trout

This study characterizes immunoglobulin light chain (IgL) expression and variable family usage in rainbow trout. IgL transcripts were generated by 5' RACE from both immune and TNP-KLH immunized fish. Phylogenetic analysis revealed that the IgL variable regions clustered into seven different families: three kappa families (two newly described in this study), three sigma families, and a single lambda family. IgL1 and IgL3 transcripts expressing identical variable regions were identified and genomic analysis revealed that the two isotypes are co-localized on chromosomes 7, 15, 18, and 21 allowing for potential rearrangement between clusters. Fish were immunized with TNP-KLH (n = 5) and percent expression of IgL1, IgL2, IgL3, and IgL4 measured by qRT-PCR from immune tissues and magnetically sorted TNP-specific lymphocyte populations. In all samples IgL1 constituted 80-95% of the transcripts. The percentage of anti-TNP specific IgL1 transcripts was measured in naïve, unsorted, and TNP-specific cell populations of TNP-KLH fish (n = 3) and found to be significantly higher in the TNP positive cell population (21%) compared to the naïve population (1%; p = 0.02) suggesting that there is a selection of TNP specific IgL sequences.

[Effect of surgery of pulmonary cysts related to immunoglobulin light chain deposits]

INTRODUCTION

Light chain deposition disease is a rare anatomo-clinical disorder, which rarely leads to cystic lung destruction.

CASE REPORT

We report the case of a 62years old female patient with a history of a monoclonal gammopathy of unknown significance who developed progressive dyspnea. Thoracic CT-scan demonstrated a diffuse pulmonary cystic disorder with predominance in the right lower lobe. Thoracoscopic surgical resection of that lobe led to a diagnosis of non-amyloid kappa light chain deposits. Surgery also resulted in a lung volume reduction effect with clinical and functional benefits related to improved ventilation of adjacent segments.

CONCLUSION

This report of pulmonary cystic disorder related to a light chain deposition disease highlights the potential clinical and functional benefits observed after lung volume reduction surgery.

Renal tubular P-glycoprotein expression is reduced in plasma cell disorders

Background

P-glycoprotein (P-gp) transports many chemicals that vary greatly in their structure and function. It is normally expressed in renal proximal tubular cells. We hypothesized that P-gp expression influences light chain excretion. Therefore, we investigated whether renal tubular P-gp expression is altered in patients with plasma cell disorders.

Methods

We evaluated renal biopsy specimens from patients with plasma cell disorders (n = 16) and primary focal segmental glomerulosclerosis (the control group, n = 17). Biopsies were stained with an anti-P-gp antibody. Loss of P-gp expression was determined semi-quantitatively. Groups were compared for loss of P-gp expression, and clinical variables.

Results

P-gp expression loss was more severe in patients with plasma cell disorders than it was in those with glomerulonephritis (P = 0.021). In contrast, clinical and histological parameters including serum creatinine, level of urinary protein excretion, and interstitial fibrosis/tubular atrophy grade were not significantly different between the groups. P-gp expression loss increased with age in patients with plasma cell disorders (P = 0.071). This expression loss was not associated with serum creatinine, the level of urinary protein excretion or the interstitial fibrosis/tubular atrophy grade. There was no significant association between the severity of P-gp expression loss with the types and serum levels of light chains, isotypes and serum immunoglobulin levels.

Conclusion

Renal tubular P-gp expression is significantly down-regulated in patients with plasma cell disorders characterized by nephrotic range proteinuria. Additional studies are needed to determine whether reintroduction of renal tubular P-gp expression would mitigate the proximal tubular injury that is caused by free-light chains.

[The value of serum heavy/light chain immunoassay to assess therapeutic response in patients with multiple myeloma]

Objective: To assess the value of immunoglobulin heavy/light chain (HLC) immunoassay on therapeutic response in patients with multiple myeloma(MM). Methods: A total of 45 newly diagnosed MM patients were retrospectively enrolled in Peking Union Medical College Hospital from 2013 to 2016, whose 115 serum samples were consecutively collected. HLC was tested to evaluate response and compare with other methods for M protein detection. Results: ①There were 30 males and 15 females in total of whom the monoclonal immunoglobulin was IgG in 27 (IgGκ∶IgGλ 12∶15) and IgA (IgAκ∶IgAλ 9∶9) in 18. The arerage age of the studied population was 59 (range 43-80) . ② In 34 patients with serum sample at diagnosis, 32 (94.1%) had abnormal HLC ratio (rHLC) while 2 patients with IgG had normal rHLC. The percentages of abnormal rHLC was 81.8% (18/22) at partial response、50.0%(9/18) at very good complete response and 16.0%(4/25) at complete response. ③In 25 patients reaching CR, there were 13 with IgG and 12 with IgA. 4 patients equally split of IgG and IgA had abnormal rHLC at complete response. ④By monitoring the rHLC of some patients consecutively, we found that the remission of rHLC was to some extent behind the remission of SPE and IEF, or even rFLC. Conclusion: Immunoglobulin HLC detection is one feasible method for minimal residual disease detection.

[Diagnosis and treatment of kidney involvement in plasma cell diseases : Renal involvement in multiple myeloma and monoclonal gammopathies]

BACKGROUND

Kidney involvement is a common complication in patients with plasma cell diseases.

OBJECTIVE

This article outlines the spectrum of renal involvement in plasma cell dyscrasia and describes diagnostic and therapeutic measures to guide clinical management.

MATERIAL AND METHODS

Evaluation and discussion of the current literature as well as existing guidelines and recommendations of professional societies.

RESULTS

The clinical manifestations of renal involvement in plasma cell disorders are heterogeneous and range from acute cast nephropathy in multiple myeloma to rare forms of glomerulonephritis. The term monoclonal gammopathy of renal significance (MGRS) was introduced to describe kidney involvement caused by monoclonal gammopathy but without evidence for underlying malignancy. Light chain cast nephropathy is the most common renal manifestation in multiple myeloma, whereas monoclonal immunoglobulin deposition disease (MIDD) and renal light chain (AL) amyloidosis can be found in multiple myeloma and MGRS. Decisive is the extended hematological diagnostics in order to exclude the presence of a hematological neoplasm. The treatment of renal involvement in monoclonal gammopathies involves the reduction of the plasma cell clone with cytoreductive treatment. The reduction of the monoclonal protein in serum is prognostically relevant for the renal response to treatment. In the case of histological evidence of a light chain cast nephropathy, high cut-off dialysis is recommended to reduce the free light chains in serum.

CONCLUSION

The spectrum of renal manifestations in plasma cell dyscrasia has been expanded, particularly since the introduction of the term MGRS. Diagnostic and therapeutic management remain an interdisciplinary challenge.

[Classification of cardiac amyloidosis: an immunohistochemical analysis]

Objective: To evaluate the sensitivity and specificity of immunohistochemistry (IHC) in the classification of cardiac amyloidosis on endomyocardial biopsy (EMB) and heart allograft. Methods: Twenty cardiac tissues from 19 patients at Fuwai Hospital from January, 1990 to April, 2017 with histopathologic features of amyloidosis and Congo red staining positivity were included. IHC was performed with monoclonal antibodies against AA amyloid and polyclonal antibodies against transthyretin (ATTR), λ-light chain (AL-λ), κ-light chain (AL-κ), ApoAⅠ, ApoAⅡ, ApoA Ⅳ and β(2)-microglobin. The extent of interstitial staining was evaluated by light microscopy, and three patterns were recognized; these included diffuse pericellular pattern, discrete pericellular pattern, and nodular pattern. Two patterns of vascular deposition were also noted, including arterial pattern and venous pattern. Endocardial involvement was also assessed and recorded. Results: Nineteen cases were divided into three groups according to the pattern of proteins expression in specimens. The first group (5 cases) only showed single protein expression on EMB. The second group (6 cases) showed more than one protein expression, but one of them was intensely stained or any staining of any protein together with ApoA Ⅳ co-staining. The third group (8 cases) also showed more than one protein expression and all of them had intense staining. Amyloid deposits were successfully subtyped as AL-λ, ATTR, AL-κ and ApoAⅠby IHC in the former two groups with the sensitivity of 11/19. In the third group, amyloid deposits could not be subtyped by immunohistochemistry due to their poor specificity. The pericellular pattern tended to favor AL over ATTR amyloidosis and vascular deposition tended to favor ATTR. Conclusions: Amyloid deposits can be reliably subtyped in diagnostic cardiac specimens using IHC. The co-deposition of chaperon proteins, the distribution of amyloid proteins and clinical features are also auxiliary to subtype cardiac amyloidosis.

[The value of serum free light chain in differential diagnosis of monoclonal gammopathy of renal significance]

Objective: To investigate the value of serum free light chain (FLC) in differential diagnosis of monoclonal gammopathy of renal significance (MGRS). Methods: Forty-nine hospitalized patients who underwent renal biopsy in Peking Union Medical College Hospital between January 2013 and December 2015 were included. Monoclonal gammopathy was detected by serum protein electrophoresis (SPE), serum immunofixation electrophoresis (IFE), urine IFE and serum FLC. All patients were classified as MGRS (n=32) and monoclonal gammopathy of undetermined significance (MGUS) (n=17). Results: Renal lesions in MGRS subgroup included light chain amyloidosis (n=24, 75.0%), light chain deposition disease (n=7, 21.9%), and fibrillary glomerulopathy (n=1, 3.1%). Renal diseases in MGUS subgroup included membranous nephropathy (n=10), focal segmental glomerulosclerosi (FSGS) (n=3), diabetic glomerulopathy (n=1), Henoch-Schonlein purpura nephritis (n=1), anti-GBM disease concurrent with membranous nephropathy (n=1) and glomerulomegaly (n=1). Positive number of SPE, serum IFE, urine IFE and abnormal number of serum FLC ratio in MGRS subgroup were 12, 16, 23 and 30, respectively. Positive number of SPE, serum IFE, urine IFE and abnormal number of serum FLC ratio in MGUS subgroup were 11, 17, 6 and 3, respectively. MGRS and MGUS subgroups differed significantly in positive rate of serum IFE (P<0.001), as well as positive rate of urine IFE (P=0.02) and abnormal rate of serum FLC ratio (P<0.001). The sensitivity, specificity, total consistent rate of serum FLC ratio for diagnosis of MGRS were 93.8%, 82.4%, and 89.8% respectively. The sensitivity for diagnosing MGRS could be increased to 100% by combining serum FLC ratio and urine IFE. Conclusions: The significance of monoclonal gammopathy in patients with renal disease should be evaluated by renal pathology.On the premise of excluding lymphoplasmacytic malignancy, serum FLC ratio had promising diagnostic value for MGRS, which was helpful for differential diagnosis of patients who had contraindication to renal biopsy.

Characteristics of Vitamin B12 Deficiency in Patients With Plasma Cell Disorders

BACKGROUND

Although increased rates of vitamin B12 deficiency have been reported in patients with plasma cell dyscrasias (PCDs), no mechanism has been identified. Excess free light chains (FLCs) could disrupt the renal proximal tubule receptors where B12 is reabsorbed. We sought to characterize the relationship between B12 deficiency and PCDs. We hypothesized that rates of B12 deficiency would be highest in patients with PCDs with high FLC burdens.

METHODS

We reviewed the electronic medical records of 501 patients who met inclusion criteria (diagnosed PCD with documented serum B12 and FLC levels) to obtain clinical data recorded prior to patients' lowest B12 levels.

RESULTS

Overall, 20.0% of patients had low vitamin B12. There was an expected negative correlation between estimated glomular filtration rate and FLC (r_s = -0.317; P < .001). However, low B12 levels were more prevalent in patients with preserved renal function (P = .047). Low B12 was associated with lower mean corpuscular volume (P = .037).

CONCLUSION

Higher FLC burden was associated with poor kidney function but not with low B12. Low B12 was seen more commonly in patients with preserved kidney function. Mean corpuscular volume was statistically but not clinically different between patients with low and normal B12 and, therefore, may not be a reliable indicator of B12 deficiency in PCDs. Prospective studies should compare B12 metabolites with FLC levels. Detection of B12 deficiency among patients with PCDs remains important to reduce neurologic dysfunction and cytopenias, sequelae common to B12 deficiency and PCDs.

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.

Effect of specimen type on free immunoglobulin light chains analysis on the Roche Diagnostics cobas 8000 analyzer

The measurement of free immunoglobulin light chains is typically performed on serum; however, the use of alternative specimen types has potential benefits. Using the Freelite™ kappa and lambda free light chains assay on a Roche Diagnostics cobas 8000 c502 analyzer, we compared three specimen types (serum, EDTA-plasma and lithium heparin plasma separator gel-plasma) on 100 patients. Using Deming regression and eliminating outliers (limiting data to light chain concentrations below 400 mg/L), the three specimen types showed comparable results for kappa light chain concentration, lambda light chain concentration, and kappa/lambda ratio with slopes close to 1.0 and y-intercepts close to zero. EDTA-plasma showed slightly more positive bias relative to serum than lithium heparin. Analysis using EDTA-plasma and lithium heparin plasma showed comparable linearity, precision, and temperature stability. A single sample showing hook effect (not in the comparison set) gave comparable results using either plasma specimen type. For the Freelite™ kappa and lambda free light chains assay, both EDTA-plasma or lithium heparin-plasma can serve as acceptable substitutes for serum, at least for the Roche cobas 8000 analyzer.