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OBJECTIVE: Bence Jones proteinuria (BJP) refers to monoclonal free immunoglobulin light chains detected in urine, deriving from the clonal expansion of plasma cells in the bone marrow in patients with plasma cell dyscrasias, associated with monoclonal gammopathies of uncertain origin. This review summarizes routinely diagnostic procedures to assess BJP highlighting critical steps of pre-analytical, analytical, and post-analytical phases. QUALITATIVE AND QUANTITATIVE METHODS: The best option for BJP detection is the first morning void urine sample and immunofixation electrophoresis detection technique (IFE) the recommended method, with the employment of specific polyvalent antisera. Other qualitative tests for a quick evaluation of BJP are currently available. Densitometric analysis performed on the 24-hour urine is the recommended method to quantify BJP. To overcome the 24-hour collection, it is possible to use morning urine sample and correlate the assessed value of BJP to creatininuria. In addition to the traditional ones, we here reviewed screening methods currently used to avoid false negatives and reduce the time around test (TAT), together with immunochemical quantification methods for increased sensitivity, after checking BJP by IFE. Mass spectrometry emerges as a new challenge in the determination of BJP. CONCLUSIONS: The employment of different based-assays methods may be useful for diagnostic purposes to improve the accuracy of BJP monitoring in monoclonal gammopathies. [ABSTRACT FROM AUTHOR]

OBJECTIVE: Polycystic ovary syndrome (PCOS) is characterized by hyperandrogenism and hyperinsulinemia thaontrol study to investigate inflammatory and immunological parameters, such as Igt contribute to create a state of chronic low-grade inflammation. We performed an observational case-cG subclasses and free light chains (FLCs) and hemolytic complement activity (CH50) in non-obese PCOS, evaluating their relations with metabolic and hormonal parameters. PATIENTS AND METHODS: 36 subjects were studied: 16 PCOS patients (mean±SEM 27.13±1.82 age; BMI 24.1±0.9 kg/m2); 20 controls (aged 26.05±0.73; BMI 20.8 ± 0.4 kg/m2). The blood sample was collected for metabolic and hormonal parameters, IgG subclasses, k and λ FLCs, CH50. Hormones were measured by immunochemiluminometric assays; metabolic parameters by enzymatic assays; subclasses of IgG, FLCs, and CH50 were evaluated by the turbidimetric method. RESULTS: PCOS patients showed vs. controls lower IgG1, IgG2, IgG3 (mean±SEM 3.76±0.29 g/l, 2.63±0.20, 0.62±0.06, 0.34±0.08 vs. 6.49±0.35, 4.28±0.25, 0.84±0.07, 0.33±0.04, respectively) and higher levels of FLCs (k 12.22±0.71 vs. 6.03±0.30, λ 10.10±0.79 vs. 8.04±0.48 g/l) and CH50 (48.64±2.65 vs. 36.51±1.38 U/ml); we found correlation between IgG2 and free-testosterone (r=0.72, p=0.005) and CH50 and vitamin D (r=0.54, p=0.04); an inverse correlation was found between IgG1 and, respectively, ACTH (r=-0.57, p=0.02) and cortisol (r=0.78, p=0.001) in PCOS. CONCLUSIONS: In the complex scenario of low-grade inflammation in non-obese PCOS, we showed lower levels of main subclasses of IgG and higher CH50 levels, suggesting the involvement of other mechanisms other than the "classical" pathway of complement activation; FLCs could be attractive to monitor inflammation degree, disease activity and influence on hormonal status. [ABSTRACT FROM AUTHOR]

OBJECTIVE: Chronic Hepatitis C virus (HCV) infection can cause severe extrahepatic manifestations, such as mixed cryoglobulins (MC), up to the development of B cell nonHodgkin’s lymphoma (B-NHL). Mechanisms transforming of HCV infection into lymphoproliferative and/or autoimmune disorders are still poorly understood. In course of HCV infection, the sustained virus-driven antigenic stimulation may probably induce a B-cell clonal expansion. Measurements of serum free light chains (FLCs) levels, considered as a direct marker of B cell activity, are analyzed with increasing interest in clinical practice, for diagnosis, monitoring and follow-up of plasma cell dyscrasia. Syndecan-1 (CD138) is a transmembrane heparan sulfate proteoglycan expressed and actively shed by most myeloma cells. Membrane CD138 represents the major receptor protein for HCV attachment to the hepatocyte surface and high levels of circulating sCD138 levels are detected in patients at early stage of B-cell chronic lymphocytic leukemia. This study is aimed to evaluate sCD138 and FLC levels as diagnostic biomarkers of HCV-related MC with B-NHL. PATIENTS AND METHODS: We enrolled 35 HCV-MC-NHL patients, characterized for the specific type of cryoglobulins, and 25 healthy blood donors (HBD) as negative control. Serum sCD138 levels were determined using ELISA kits specific for human sCD138. Serum FLCs were assessed by means of the turbidimetric assay. RESULTS: We found that serum levels of sCD138, as well as FLCs, were significantly higher in patients than in HBD (p<0.001). CONCLUSIONS: In agreement with the definition of HCV-driven lymphoproliferative disorders as the consequence of a multifactorial and multistep pathogenetic process, we suggest that sCD138 and FLCs could be considered putative independent markers of worsening progression of the disease. [ABSTRACT FROM AUTHOR]

Summary: 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. [ABSTRACT FROM AUTHOR]

OBJECTIVE: A still uncertain association between vitamin D levels and HCV chronic liver diseases has been reported. Increased levels of serum-ree light chains (FLCs) and an altered k/λ FLC ratio correlate with Mixed Cryoglobulinemia (MC) vasculitis and/or B-cell non-Hodgkin's lymphoma in HCV-positive patients. We aimed to investigate the possible role of vitamin D, vitamin D Binding Protein (DBP), and FLCs levels as a tool for discriminating different stages of HCV- related MC and chronic liver diseases. PATIENTS AND METHODS: Sixty-five untreated patients were retrospectively enrolled and 21 healthy blood donors (HBD) were used as controls. Vitamin D, DBP, FLCs, and cryoglobulins levels were measured. Based on cryoglobulins, patients were divided in three subgroups (without cryoglobulins, type II, and type III). RESULTS: We didn't find any significant differences in vitamin D and DBP levels between HCV patients' main groups and HBD. Serum FLCs levels were significantly higher in HCV patients than in HBD. FLCs ratio among patients' subgroups did not reveal differences. CONCLUSIONS: Our results confirm the presence of an increased serum level of FLCs in HCV patients and suggest that nor vitamin D and DBP or FLC levels can be considered reliable biomarkers for discriminating different stages of HCV-associated chronic liver diseases and/or HCV-associated extrahepatic manifestation. We confirm that serological FLCs levels are signifi- cantly higher in patients than in HBD as a signature of B cell activation in course of HCV infection. [ABSTRACT FROM AUTHOR]

OBJECTIVE: Mixed Cryoglobulinemia is the most well-known Hepatitis C Virus (HCV)-associated extrahepatic manifestation. MC is both an autoimmune and B-lymphoproliferative disorder. Cryoglobulins (CGs) are classified into three groups according to immunoglobulin (Ig) composition: type I is composed of one isotype or Ig class. Type II and type III mixed CGs are immune complexes composed of polyclonal IgGs acting as autoantigens and mono, polyclonal or oligoclonal IgM with rheumatoid factor activity. IgG1 and IgG3 are the predominant subclasses involved. This study shows the simultaneous presence of IgG-RF and IgG3, supporting the hypothesis of an involvement of this subclass in the initiation of early stages of CGs. PATIENTS AND METHODS: We describe a case series of six HCV-positive patients, all of whom had peripheral neuropathy and transient ischemic attacks, presenting cryoprecipitates formed by IgG3 and IgG1. Cryoprecipitate IgG subclass research was carried out by immunofixation electrophoresis by using antisera against IgG1, IgG2, IgG3, and IgG4. RESULTS: Our six patients presented with an immunochemical pattern characterized by the mere presence of IgG1 and IgG3 subclasses with probable RF activity and one of these six patients exhibited monoclonal IgG3 in his cerebrospinal fluid. CONCLUSIONS: We can hypothesize that the IgG passage through the blood-brain barrier could have contributed to the cause of TIAs, through a mechanism involving the precipitation of circulating immune complexes formed by the two subclasses in the intrathecal vessels. [ABSTRACT FROM AUTHOR]

Calprotectin (CLP) is a calcium-binding protein produced by neutrophils and monocytes in the course of inflammation. Today, the role of faecal CLP in chronic IBD is well known, but in recent years attention has shifted towards circulating CLP. In fact, this molecule can be measured in different biological fluids: blood, saliva and urine, using different analytic methods that are described in this review. Furthermore, different data confirm the relevant role of serum CLP in autoimmune diseases. In this review we will highlight the correlation between high levels of circulating CLP and specific autoantibodies of major autoimmune pathologies paving the way to the employment of CLP measurement as useful biomarker for monitoring outcome in different pathologies., (© The Author(s) 2023. Published by Oxford University Press on behalf of the British Society for Rheumatology.)

Prolonged B cells stimulation due to the Hepatitis C virus (HCV) can result in autoimmunity, stigmatized by rising levels of cryoglobulins (CGs), the rheumatoid factor (RF), and free light chains (FLC) of immunoglobulins (Ig) associated with a range of symptoms, from their absence to severe cryoglobulinemic vasculitis and lymphoma. Here, we aimed to identify an immunological signature for the earliest stages of vasculitis when cryoprecipitate is still not detectable. We firstly analyzed the IgG subclasses, FLC, and RF in 120 HCV-RNA-positive patients divided into four groups according to the type of cryoprecipitate and symptoms: 30 asymptomatic without cryoprecipitate (No Cryo), 30 with vasculitis symptoms but without CGs that we supposed were circulating but still not detectable (Circulating), 30 type II and 30 type III mixed cryoglobulinemia (Cryo II and Cryo III, respectively). Our results revealed that patients with supposed circulating CGs displayed a pattern of serological parameters that closely resembled Cryo II and Cryo III, with a stronger similarity to Cryo II. Accordingly, we analyzed the groups of Circulating and Cryo II for their immunoglobulin heavy chain (IgH) and T-cell receptor (TCR) gene rearrangements, finding a similar mixed distribution of monoclonal, oligoclonal, and polyclonal responses compared to a control group of ten HCV-RNA-negative patients recovered from infection, who displayed a 100% polyclonal response. Our results strengthened the hypothesis that circulating CGs are the origin of symptoms in HCV-RNA-positive patients without cryoprecipitate and demonstrated that an analysis of clonal IGH and TCR rearrangements is the best option for the early diagnosis of extrahepatic complications.

Background: Inflammation plays a pivotal role in the pathophysiology of asthma. Free light chains (FLC) can cause inflammation by mast cell antigen-activation. Serum immunoglobulin (Ig) FLC κ, but not λ, were shown elevated in adult males with asthma. We sought to investigate if serum Ig FLC concentrations are affected by asthma severity and their relationships with inflammatory outcomes. Methods: By using immunoassays, we measured serum κ and λ Ig FLCs in 24 severe persistent asthma patients, 15 patients with moderate persistent asthma, 15 steroid-naïve mild persistent asthma patients and 20 healthy control subjects in a cross-sectional observational study. Total and specific serum IgE concentrations, fractional exhaled nitric oxide (F E NO), lung function, peripheral blood eosinophils and neutrophils, and C reactive protein (CRP) were also measured. Results: Serum κ FLC concentrations were elevated in severe asthma patients compared mild asthma patients ( p < 0.05) and healthy subjects ( p < 0.05). Serum λ FLCs were higher in severe asthma patients than in healthy subjects ( p < 0.05) and correlated with blood eosinophil counts (percentage, κ: r = 0.51, p = 2.9678 -6 ; λ: r = 0.42, p = 1.7377 -4 ; absolute values, κ: r = 0.45, p = 6.1284 -5 ; λ: r = 0.38, p = 7.8261 -4 ), but not with total or specific serum IgE. In severe asthma patients, serum Ig FLC correlated with serum CRP (κ: r = 0.33; p = 0.003; λ: r = 0.38, p = 8.8305 -4 ) and blood neutrophil cell counts (percentage, κ: r = 0.31; p = 0.008; λ: r = 0.29, p = 0.01; absolute values, κ: r = 0.40; p = 3.9176 -4 ; λ: r = 0.40, p = 4.5479 -4 ), were elevated in subjects with blood eosinophilia (≥300 cells/µL) ( n = 13) compared with non-eosinophilic subjects ( n = 10) (κ: 19.2 ± 1.2 mg/L versus 12.1 ± 1.3 mg/L, p < 0.001; λ: 27.2 ± 2.6 mg/L versus 16.8 ± 2.5 mg/L, p < 0.01), but were similar in atopic ( n = 15) versus nonatopic subjects ( n = 9) (κ: p = 0.20; λ: p = 0.80). Serum FLC were negatively correlated with lung function tests, including forced expiratory volume in one second (FEV1) (κ: r = -0.33; p = 0.0034; λ: r = -0.33; p = 0.0035), and FEV 1 /forced vital capacity ratio (κ: r = -0.33; p = 0.0034; λ: r = -0.33; p = 0.0036). Conclusion: Serum Ig FLCs are elevated in severe asthma adults and might represent new surrogate markers of inflammation. The pathophysiological implications of these findings require further research. This study was approved by the ethics committee of the University Hospital Agostino Gemelli Foundation and Catholic University of the Sacred Heart (approval number P/1034/CE2012)., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Basile, Santini, Napodano, Macis, Pocino, Gulli, Malerba, Bush, Adcock and Montuschi.)

The antibody-related immune response is mediated by immunoglobulins (Igs), soluble circulating glycoproteins produced by activated B cells that, upon the recognition of specific epitopes on pathogen surfaces, activate, proliferate, and differentiate into antibody-secreting plasma cells. Although the antibodies are effectors of the humoral immune adaptive response, their overproduction in response to a dysregulated proliferation of clonal plasma cell production in tumoral conditions (i.e., multiple myeloma), enriches the serum and urinary matrices, assuming the crucial role of biomarkers. Multiple myeloma (MM) is a plasma cell dyscrasia characterized by the expansion and accumulation of clonally activated plasma cells in bone marrow, determining the release of high amounts of monoclonal component (MC) that can be detected as intact immunoglobulin (Ig), immunoglobulin fragments, or free light chains (FLCs). The importance of detecting biomarkers for the diagnosis, monitoring, and prognosis of diseases is highlighted by the international guidelines that recommend specific assays for the analysis of intact Igs and FLC. Moreover, a developed assay called Hevylite ® allows for the quantification of immunoglobulins that are both involved (iHLC) and not involved (uHLC) in the tumor process; this is a fundamental aspect of following up the patient's workup and evaluating the progression of disease, together with the treatments response. We here summarize the major points of the complex scenario involving monoclonal gammopathies and MM clinical management in view of advantages derived for the use of Hevylite ® .

Hepatocellular carcinoma (HCC) represents a worldwide health matter with a major care burden, high prevalence, and poor prognosis. Its pathogenesis mainly varies depending on the underlying etiological factors, although it develops from liver cirrhosis in the majority of cases. This review summarizes the role of the most interesting soluble factors as biomarkers for early diagnosis and as recommended targets for treatment in accordance with the new challenges in precision medicine. In the premalignant environment, inflammatory cells release a wide range of cytokines, chemokines, growth factors, prostaglandins, and proangiogenic factors, making the liver environment more suitable for hepatocyte tumor progression that starts from acquired genetic mutations. A complex interaction of pro-inflammatory (IL-6, TNF-α) and anti-inflammatory cytokines (TGF-α and -β), pro-angiogenic molecules (including the Angiopoietins, HGF, PECAM-1, HIF-1α, VEGF), different transcription factors (NF-kB, STAT-3), and their signaling pathways are involved in the development of HCC. Since cytokines are expressed and released during the different stages of HCC progression, their measurement, by different available methods, can provide in-depth information on the identification and management of HCC.

Introduction: In this pilot study we have taken a novel functional approach to assess whether differences exist in the activity of key genes involved in the response to radiation and oxidative stress between patients with radiation cystitis., Materials and Methods: Arm 1 consisted of patients who had previously been treated for prostate cancer and who had received definitive radiation treatment and had subsequently developed cystitis and/or proctitis and were being treated by hyperbaric oxygen (HBO). Arm 2 consisted of patients who had never been treated by radiation but who were scheduled for HBO treatment for another pathology. The genes chosen for the study were HMOX1, NOS2, SOD2, TNFα, IL-6 and TGFβ. Blood and urine was collected pre and post HBO treatment., Results: Gene expression showed a significant difference in NOS2 (p = 0.0178) and TNFα (p = 0.037) between the control and cystitis patients. The plasma levels of VEGF-A were significantly elevated in cystitis patients and there was a strong trend for significant overexpression in urine. Comparing pre and post-dive samples showed little difference in both groups of patients except for VEGF-A which was reduced after the dive in plasma from cystitis patients., Conclusions: This study uncovered some physiological differences in patients with radiation-induced cystitis using HBO treatment as a stimulus to induce mild oxidative stress. Further research is ongoing to assess whether the acute exposure to HBO might be a physiological screening tool to identify patients susceptible to chronic radiation toxicity., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2022 The Authors.)

The aim was to evaluate the longitudinal association between basal serum adiponectin and repeated measurements of skin thickness during 12 months of follow-up in systemic sclerosis (SSc) patients. We enrolled SSc patients with disease duration > 2 years in a prospective observational study. Skin thickness was measured at baseline and after 12 months of follow-up with modified Rodnan skin score (mRSS). Baseline serum adiponectin was determined using a commercial ELISA kit. We enrolled 66 female SSc patients (median age 54 years, IQR 42−62 years). The median disease duration was 12 (IQR 8−16) years and median baseline serum adiponectin was 9.8 (IQR 5.6−15.6) mcg/mL. The median mRSS was 10 (IQR 6−18) at baseline and 12 (IQR 7−18) at follow-up. A significant correlation was observed between baseline serum adiponectin and disease duration (r = 0.264, p < 0.05), age (r = 0.515, p < 0.0001), baseline mRSS (r = −0.303, p < 0.05), and mRSS at follow-up (r = −0.322, p < 0.001). In multiple regression analysis, only mRSS at follow-up showed an inverse correlation with baseline serum adiponectin (β = −0.132, p < 0.01). The reduction in serum adiponectin levels is correlated with skin thickness.

Oxidative and inflammatory damage underlie several conditions related to male infertility, including varicocele. Free light chains of immunoglobulins (FLCs) are considered markers of low-grade inflammation in numerous diseases. Coenzyme Q10 (CoQ10), a lipidic antioxidant and anti-inflammatory compound, is involved in spermatozoa energy metabolism and motility. We aimed to evaluate FLCs' seminal levels in patients with varicocele in comparison to control subjects and to correlate them with CoQ10 and Total Antioxidant Capacity (TAC) in human semen. Sixty-five patients were enrolled. Semen analysis was performed; patients were divided into three groups: controls, 12 normozoospermic patients, aged 34 (33-41) years; varicocele (VAR), 29 patients, aged 33 (26-37) years; and idiopathic, 24 oligo-, astheno- and oligoasthenozoospermic patients aged 37 (33.5-40.5) years. FLCs (κ and λ) were assayed by turbidimetric method; CoQ10 by HPLC; TAC by spectrophotometric method. λ FLCs showed a trend toward higher levels in VAR vs. controls and the idiopathic group. VAR showed a trend toward lower κ FLCs levels vs. the other two groups. When comparing κ/λ ratio, VAR showed significantly lower levels vs. controls and idiopathic. Moreover, CoQ10 seminal levels showed higher levels in VAR and idiopathic compared to controls. Data reported here confirm lower levels of κ/λ ratio in VAR and suggest a possible application in personalized medicine as clinical biomarkers for male infertility.

Immunoglobulins free light chains (FLCs) are assayable in several biological fluids. Currently, there are no reports on FLCs in seminal plasma. The aims of our study were to investigate the presence and detectability of FLCs in seminal plasma and to evaluate the usefulness of this assay in the diagnostic approach to infertile patients. We enrolled 61 patients aged 18-50 years. Semen analysis was performed. They were divided into four groups: controls-normozoospermic, 10 patients, mean ± SEM age 35 ± 1.5 years; varicoceles (VAR), 18 patients aged 24.3 ± 0.96 years; inflammatory (INF) seminal fluids, 24 patients, aged 38.8 ± 2.2 years; and varicoceles and inflammatory (VAR/INF) seminal fluids, 9 patients, aged 29.5 ± 0.71 years. A trend towards higher λ FLCs levels was evidenced in the INF and VAR/INF groups. κ FLCs were higher in normozoospermic patients with lower levels in VAR, both isolated and associated with inflammatory parameters. This differential pattern of the two types of FLCs reached statistical significance when comparing κ/λ ratio, with significant lower levels in VAR vs controls. This is the first report of FLCs assay in seminal plasma. We can hypothesize that λ FLCs are increased in inflammatory processes, whether κ FLCs seem to be influenced by other molecular mechanisms related to varicocele., (© 2021 Wiley-VCH GmbH.)

Introduction: The involvement of complement system in the phenotypic expression of systemic sclerosis (SSc) is a debated topic. We aimed to assay complement fractions in SSc patients and to correlate their levels with the clinical course of disease., Key Points: 1. CH50 is increased in SSc patients compared to HC; 2. Serum C2 levels are increased in SSc patients compared to HC; 3. CH50 may represent a biomarker of skin and lung fibrosis severity in SSc patients., Method: Complement hemolysis 50% (CH50), C2, C3 and C4 levels have been assessed in 85 SSc patients and 47 healthy controls (HC)., Results: SSc patients displayed a statistically significant higher value of CH50 [76.3 U/mL (IQR 65.8-89.4 U/mL) vs. 29.6 U/mL (IQR 24.7-34 U/mL); p < 0.0001] and of C2 [26.1 mg/L (IQR 24.1-32.1 mg/L) vs. 22.7 mg/L (IQR 20.6-24.4 mg/L); p < 0.0001] if compared to HC. Patients with diffuse cutaneous SSc (dcSSc) had higher levels of CH50 than patients with limited cutaneous SSc (lcSSc) [83.6 U/mL (IQR 72.3-102.7 U/mL) vs. 71.3 U/mL (IQR 63.7-83.6 U/mL); p = 0.003]. SSc patients with interstitial lung disease (ILD) had higher CH50 levels if compared to SSc patients without ILD [79.6 U/mL (IQR 68.3-97.4 U/mL) vs. 69.7 U/mL (54.6-85.7 U/mL); p = 0.042]. A positive linear correlation existed between CH50 and the modified Rodnan Skin Score (mRSS) (r = 0.285, p = 0.008) and disease severity scale (DSS) (r = 0.285, p = 0.005); a negative linear correlation was demonstrated between CH50 and the diffusing capacity of carbon monoxide (DLco) (r = -0.252, p = 0.012). In multiple linear regression analysis, only DSS was significant ( p = 0.01, beta coefficient 2.446)., Conclusions: Our results show an increment of CH50 and serum C2 levels in SSc patients in comparison to HC; we retain that CH50 may represent a biomarker of disease severity and of skin and lung fibrosis in these patients.

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., (Copyright © 2022 Elsevier Inc. All rights reserved.)