Efficient separation of organic anions in beverages using aminosilane-functionalized capillary electrophoresis with contactless conductivity detection.

BACKGROUND: Capillary electrophoresis (CE) has the advantage of rapid anion analysis, when employing a reverse electroosmotic flow (EOF). The conventional CE method utilizes dynamic coatings with surfactants like cetyltrimethylammonium bromide (CTAB) in the run buffer to reverse the EOF. However, this method suffers from very slow equilibration leading to drifting effective migration times of the analyte anions, which adversely affects the identification and quantification of peaks. Permanent coating of the capillary surface may obviate this problem but has been relatively little explored. Thus, permanent capillary surface modification by the covalent binding of 3-aminopropyltriethoxysilane (APTES) was studied as an alternative. RESULTS: This study investigates the effect of APTES concentration for surface functionalization on EOF mobility, separation efficiency, and reproducibility of anion separation. The performance data was complemented by X-ray photoelectron spectroscopy (XPS) and contact angle (CA) measurements. The XPS measurements showed that the coverage with APTES was dependent on its concentration in the coating solution. The XPS measurements correlated well with the EOF values determined for the capillaries tested. A standard mixture of 21 anions could be baseline separated within 10 min in the capillaries with lower EOF, but not in the capillary with the highest EOF as the residence time of the analytes was too short in this case. Compared to conventional dynamic coating with CTAB, APTES-functionalized capillaries provide faster equilibration and long-term EOF stability. The application of APTES-functionalized capillaries in analyzing different beverages demonstrates the precision, reliability, and specificity in determining organic anions, providing valuable insights of their compositions. SIGNIFICANCE: APTES coating on capillaries provides a facile approach to achieve a permanent reversal of the stable EOF to determine anions. The control of the coverage via the concentration of the reagent solution allows the tailoring of the EOF to different needs, a faster EOF for less complex samples where resolution is not challenging, while a lower EOF for higher complex samples where the focus is on separation efficiency. This enhancement in efficiency and sensitivity has been applied to analyzing organic acids in several beverages.

[Diagnostic significance of C4d in membranous nephropathy]. / Importancia diagnóstica del C4d en la nefropatía membranosa.

INTRODUCTION: Membranous nephropathy (MN) is the most common cause of primary nephrotic syndrome in adults (20-30%). Light microscopy shows thickening of glomerular basement membrane with appearance of spikes. These histological findings are not evident in early forms, in which case the granular deposition pattern of IgG and/or C3 in the basement membrane by immunofluorescence (IF) constitutes the diagnostic tool that allows to differentiate it from minimal change disease (MCD). Complement system plays a key role in the pathophysiology of MN. C4d is a degradation product and a marker of the complement system activation. C4d labelling by immunohistochemical (HI) technique can help in the differential diagnosis between both glomerulopathies NM and MCD when the material for IF is insufficient and light microscopy is normal. Our objective was to explore the discrimination power of C4d to differentiate between MN and MCD in renal biopsy material. METHODS: Paraffin-embedded samples were recovered from renal biopsies with a diagnosis of MN and MCD performed between 1/1/2008 and 4/1/2019. IH staining was performed by immunoperoxidase technique using a rabbit anti-human C4d polyclonal antibody. RESULTS: In all cases with MN (n = 27, 15 males) with a median age of 63 (range: 18-87) years, C4d deposits were detected. In 21 cases with MCD (12 males) with a median age of 51 (range: 18-87) years, the C4d marking was negative in every samples. CONCLUSION: The results indicate that the marking of the renal biopsy with C4d is a useful tool for the differential diagnosis between NM and MCD.

Introducción: La nefropatía membranosa (NM) es la causa más frecuente de síndrome nefrótico primario en adultos (20-30%). En la microscopia óptica se observa engrosamiento de membrana basal glomerular con aparición de espigas. Estos hallazgos histológicos no son evidentes en formas tempranas, en cuyo caso el patrón de depósito granular de IgG y/o C3 en la membrana basal por inmunofluorescencia (IF) permite diferenciarla de enfermedad por cambios mínimos (ECM). El sistema del complemento juega un papel central en la fisiopatología de la NM. C4d es producto de degradación y un marcador de la activación del complemento. La marcación con C4d en muestras de biopsias renales, por técnica de inmunohistoquímica (IH) puede colaborar en el diagnóstico diferencial entre ambas glomerulopatías. Nuestro objetivo fue explorar el poder de discriminación del C4d para diferenciar NM de ECM en material de biopsias renales. Métodos: Se recuperaron muestras en parafina de biopsias renales con diagnóstico de NM y ECM realizados entre 1/1/2008 y 1/4/2019. Se realizaron tinciones de IH por técnica de inmunoperoxidasa con C4d usando un anticuerpo policlonal antihumano de conejo. Resultados: En todos los casos con NM (n = 27, 15 hombres) con mediana de edad de 63 (rango: 18-86) años se detectaron depósitos de C4d. En los 21 casos con ECM (12 hombres) con mediana de edad de 51 (rango: 18-87) años la marcación de C4d fue negativa. Conclusión: Los resultados indican que la marcación de la biopsia renal con C4d es una herramienta útil para el diagnóstico diferencial entre NM y ECM.

C4d expression in focal segmental glomerulosclerosis.

BACKGROUND: There is a little information about of expression of C4d (complement fragment) in Focal segmental glomerulosclerosis (FSGS) subtypes. Our aim was to determine the expression of C4d in FSGS subtypes in percutaneous native renal biopsies in a second-level hospital and its correlation with clinical, biochemical and histological variables. MATERIAL AND METHODS: A retrospective study in paraffin blocks of patients with biopsy with FSGS aged 16-65 years, indistinct sex, not diabetic or obese. Immunohistochemistry was performed for C4d and their expression was analyzing in non-sclerosed glomerular capillaries (GC) and sclerosis areas (SA). Clinical and biochemical variables were recorded. The cases were divided into C4d positive and C4d negative groups and compared. The correlation between C4d staining scores in CG and SA with clinical and biochemical variables were analyzed. RESULTS: Twenty samples were analyzed, 4 for each subtype. At the time of biopsy average age 38.8 ±â€¯18.6 years, 65% male, 8.7% were hypertension. The percentage of positivity for C4d was 40% in GC, 30% SA and 35% in mesangium. The highest expression was for cellular and collapsing subtypes. C4d positivity cases had increased proteinuria (p = 0.035). A significant correlation was found between percentage of C4d expression in CG with SA (p = 0.012) and SA with tubular atrophy and interstitial fibrosis (p < 0.05). CONCLUSIONS: C4d expression in FSGS predominated in the cellular and collapsing subtypes, which translates complement activation. C4d is a possible surrogate marker in GSFS.

Role of C4d immunohistochemical marker in the diagnosis of bullous pemphigoid: A cross-sectional study.

Objective To determine the diagnostic utility of C4d immunohistochemical marker in cases of bullous pemphigoid by calculating the sensitivity, specificity, positive predictive value and negative predictive value. Methods We conducted an exploratory study (retrospectively and prospectively) from January 2017 to June 2022. All direct immunofluorescence proven cases of bullous pemphigoid were included in the study while cases with inadequate tissue for immunohistochemistry studies were excluded. Results Among the 57 cases of bullous pemphigoid, 49 showed positivity for C4d marker. All the ten control cases of inflammatory dermatoses were negative for C4d staining. A sensitivity of 86%, a specificity of 100%, a positive predictive value of 100% and a negative predictive value of 55.56% were calculated with a confidence interval of 95%. Conclusion Direct immunofluorescence on fresh or frozen skin tissue remains the gold standard. But in circumstances where direct immunofluorescence facilities are not available, C4d immunohistochemistry marker staining on formalin-fixed paraffin-embedded material submitted for standard microscopic investigation can, in most cases, confirm the diagnosis of bullous pemphigoid, obviating the need for a second biopsy. Limitation It is a single centre study. Selection bias may come into play.

Escalated complement activation during hospitalization is associated with higher risk of 60-day mortality in SARS-CoV-2-infected patients.

BACKGROUND: The complement system, an upstream recognition system of innate immunity, is activated upon SARS-CoV-2 infection. To gain a deeper understanding of the extent and duration of this activation, we investigated complement activation profiles during the acute phase of COVID-19, its persistence post-recovery and dynamic changes in relation to disease severity. METHODS: Serial blood samples were obtained from two cohorts of hospitalized COVID-19 patients (n = 457). Systemic complement activation products reflecting classical/lectin (C4d), alternative (C3bBbP), common (C3bc) and terminal pathway (TCC and C5a) were measured during hospitalization (admission, days 3-5 and days 7-10), at 3 months and after 1 year. Levels of activation and temporal profiles during hospitalization were related to disease severity defined as respiratory failure (PO2/FiO2 ratio <26.6 kPa) and/or admission to intensive care unit, 60-day total mortality and pulmonary pathology after 3 months. FINDINGS: During hospitalization, TCC, C4d, C3bc, C3bBbP and C5a were significantly elevated compared to healthy controls. Severely ill patients had significantly higher levels of TCC and C4d (p < 0.001), compared to patients with moderate COVID-19. Escalated levels of TCC and C4d during hospitalization were associated with a higher risk of 60-day mortality (p < 0.001), and C4d levels were additionally associated with chest CT changes at 3 months (p < 0.001). At 3 months and 1 year, we observed consistently elevated levels of most complement activation products compared to controls. CONCLUSION: Hospitalized COVID-19 patients display prominent and long-lasting systemic complement activation. Optimal targeting of the system may be achieved through enhanced risk stratification and closer monitoring of in-hospital changes of complement activation products.

Urinary C4d and progression of kidney disease in IgA vasculitis.

BACKGROUND: IgA vasculitis nephritis is the most common secondary IgA nephropathy. Urinary C4d have been identified associated with the development and progression in primary IgA nephropathy. However, its role in kidney disease progression of IgA vasculitis nephritis is still unclear. METHODS: This study enrolled 139 patients with IgA vasculitis nephritis (IgAVN), 18 healthy subjects, 23 Focal segmental glomerulosclerosis patients and 38 IgA nephropathy (IgAN) patients. Urinary C4d levels at kidney biopsy were measured using enzyme-linked immunosorbent assay. The association between urinary C4d/creatinine and kidney disease progression event, defined as 40% eGFR decline or ESKD, was assessed using Cox proportional hazards models and restricted cubic splines. RESULTS: The levels of urinary C4d/creatinine in IgAVN and IgAN patients were higher than in healthy controls. Higher levels of urinary C4d/creatinine were associated with higher proteinuria and severe Oxford C lesions and glomerular C4d deposition. After a median follow-up of 52.79 months, 18 (12.95%) participants reached composite kidney disease progression event. The risk of kidney disease progression event was higher with higher levels of ln (urinary C4d/creatinine). After adjustment for clinical data, higher levels of urinary C4d/creatinine were associated with kidney disease progression in IgA vasculitis nephritis (per ln transformed urinary C4d/creatinine, hazard ratio (HR) =1.573, 95% confidence interval (CI) 1.101-2.245; P = 0.013). Compared to the lower C4d/creatinine group, hazard ratio was 5.539(95%CI, 1.135-27.035; P = 0.034) for the higher levels group. CONCLUSIONS: Higher levels of urinary C4d/creatinine were associated with kidney disease progression event in patients IgAVN.

Evaluation of C4d expression and staining patterns by immunohistochemistry in renal biopsy samples with focal segmental glomerulosclerosis and minimal change disease.

INTRODUCTION: C4d is an activation product of lectin pathway of complement. Glomerular deposition of C4d is associated with poor prognosis in different types of immune-related glomerulonephritis. The present study was conducted to investigate expression level of C4d and its staining pattern in renal biopsy of patients with focal segmental glomerulosclerosis (FSGS) and minimal change disease (MCD) by immunohistochemistry method. MATERIALS AND METHODS: In this retrospective cross-sectional study, renal biopsy specimens from 46 samples of MCD, 47 samples of FSGS, and 15 samples without glomerular disease as the controls, were subjected to immunohistochemistry staining with C4d. Demographic characteristics and information obtained from light and electron microscopy (EM) of patients were also extracted from their files. RESULTS: C4d positive staining was observed in 97.9 % of FSGS and 43.5 % of MCD samples, which showed a statistically significant difference (P < 0.001). The sensitivity and specificity of C4d expression for diagnosing FSGS were 97.9 % and 56.5 %, respectively. There was no significant correlation between C4d expression and any of the light and electron microscopy findings, including presence of foam cells, mesangial matrix expansion, interstitial fibrosis and tubular atrophy, and basement membrane changes in MCD patients. Also, no significant correlation was observed between C4d expression and clinical symptoms of proteinuria or prolonged high level of creatinine in patients with MCD. DISCUSSION AND CONCLUSION: The expression of C4d marker had a good sensitivity and negative predictive value in the diagnosis of FSGS.

Complement C4d as a biomarker for systemic lupus erythematosus and lupus nephritis.

Background: Increasing studies in the last decade have led to the widespread understanding that C4d, a split product of complement component 4 (C4), is a potential biomarker for systemic lupus erythematosus (SLE) and lupus nephritis (LN).Purpose: The aim of this review is to summarize the highlights of studies investigating the use of C4d as a biomarker for diagnosing and monitoring SLE and LN patients.Data collection: we searched PubMed/Medline and Wanfang databases using the terms "C4d and systemic lupus erythematosus", "C4d and lupus nephritis", and "Complement C4d".Results: The deposition of C4d on circulating blood cells has been shown in several clinical studies to be a potential diagnostic marker that can be used to monitor patients with SLE. In addition, C4d deposits on circulating blood cells may be a helpful diagnostic marker for LN, one of the most severe complications of SLE. Meanwhile, studies utilizing renal biopsy specimens have indicated that C4d deposition in the renal peritubular capillaries of LN patients may predict more severe LN or a worse patient prognosis. Generally, a high plasma C4d level and a high plasma C4d/C4 ratio may also be promising indicators that can be used to monitor patients with SLE and LN.Conclusions: C4d detection may be a novel strategy for further clinical prediction and therapy.

Association between urinary C4d levels and disease progression in IgA nephropathy.

BACKGROUND: C4d mesangial deposition, a hallmark of lectin pathway activation in IgA nephropathy (IgAN), has been shown to be associated with risk of kidney failure. To date, the relationship between urinary C4d and renal outcome remain unelucidated. METHODS: A total of 508 patients with biopsy-proven IgAN were enrolled in this study, whose baseline urine samples at the time of biopsy were collected and the levels of urinary C4d were quantified by enzyme-linked immunosorbent assay. The time-averaged C4d (TA-C4d) and the change in proteinuria were measured in sequential urine samples obtained from IgAN patients. The kidney progression event was defined as a 50% estimated glomerular filtration rate (eGFR) decline or end-stage kidney disease (ESKD) or death. RESULTS: After a median follow-up of 36 months, 70 (13.8%) of the participants reached the kidney progression event. Higher levels of urinary C4d/creatinine were found to be associated with decreased eGFR, massive proteinuria, lower serum albumin levels, hypertension, and severe Oxford E and T scores. Upon adjusting for traditional risk factors (including demographics, eGFR, proteinuria, hypertension, Oxford pathologic score, and immunosuppressive therapy), elevated levels of urinary C4d/creatinine were independently associated with an increased risk of CKD progression (adjusted HR per standard deviation increment of log-transformed C4d/creatinine: 1.46; 95% CI: 1.04 to 2.06; P=0.030). In reference to the low C4d group, the risk of poor renal outcome increased for the high C4d group (adjusted HR: 1.93; 95% CI: 1.05 to 3.54; P=0.033). Additionally, a low baseline C4d level was independently assosicated with a favorable proteinuria response to immunosuppressive therapy at three months (adjusted relative risk: 2.20; 95% CI: 1.04-4.63, P=0.038). CONCLUSION: The urinary C4d, serving as a non-invasive biomarker, is associated with the progression of IgAN and holds the potential to predict proteinuria response in this disease.

Significance of C4d expression in peritubular capillaries concurrent with microvascular inflammation in for-cause biopsies of ABO-incompatible renal allografts.

BACKGROUND: Pathologic diagnosis of antibody-mediated rejection (ABMR) in ABO-incompatible (ABOi) transplantation patients is often challenging because patients without ABMR are frequently immunopositive for C4d. The aim of this study was to determine whether C4d positivity with microvascular inflammation (MVI), in the absence of any detectable donor-specific antibodies (DSAs) in ABOi patients, could be considered as ABMR. METHODS: A retrospective study of 214 for-cause biopsies from 126 ABOi kidney transplantation patients was performed. Patients with MVI score of ≥2 and glomerulitis score of ≥1 (n = 62) were divided into three groups: the absolute ABMR group (DSA-positive, C4d-positive or C4d-negative; n = 36), the C4d-positive group (DSA-negative, C4d-positive; n = 22), and the C4d-negative group (DSA-negative, C4d-negative; n = 4). The Banff scores, estimated glomerular filtration rates (eGFRs), and graft failure rates were compared among groups. RESULTS: C4d-positive biopsies showed higher glomerulitis, peritubular capillaritis, and MVI scores compared with C4d-negative specimens. The C4d-positive group did not show significant differences in eGFRs and graft survival compared with the absolute ABMR group. CONCLUSION: The results indicate that C4d positivity, MVI score of ≥2, and glomerulitis score of ≥1 in ABOi allograft biopsies may be categorized and treated as ABMR cases.

Utility of C4d Immunohistochemistry as an Adjunct Stain in Diagnostic Renal Pathology of Glomerular Diseases.

C4d is a byproduct of the activation of the classic and lectin complement pathways. Being routinely used as a marker for antibody-mediated rejection, the significance of C4d in native kidney disease is currently being widely studied. We evaluated glomerular and extraglomerular C4d staining in 82 biopsies of proliferative and nonproliferative glomerulonephritis diagnosed in our institution. The staining pattern of C4d was tabulated in various glomerular diseases. All biopsies of membranous nephropathy including membranous lupus nephritis (Class V) and immune complex-mediated membranoproliferative glomerulonephritis (MPGN) consistently showed C4d deposits along glomerular basement membrane mirroring the location of immunoglobulin and complement in these conditions. Conversely, other glomerular diseases like IgA nephropathy, postinfectious glomerulonephritis, focal segmental glomerulosclerosis, minimal change disease, and diabetic nephropathy showed variable mesangial and capillary wall C4d deposits. To summarize, the consistent pattern of C4d staining in membranous nephropathy (primary and secondary)and immune complex-mediated MPGN can be used as a valuable adjunct tool in establishing the diagnosis, especially when immunofluorescence findings are limited by inadequate sampling.C4d reactivity in other glomerular diseases are variable and may not aid as a diagnostic tool in renal biopsy evaluation.

Antibody Mediated Rejection is not Associated with Worse Survival in Adherent Heart Transplant Patients in the Contemporary Era.

Background: C4d immunostaining of surveillance endomyocardial biopsies (EMB) and testing for donor specific antibodies (DSA) are routinely performed in the first year of heart transplantation (HTx) in adult patients. C4d and DSA positivity have not been evaluated together with respect to clinical outcomes in the contemporary era (2010-current). Methods: This was a single center, retrospective study of consecutive EMBs performed between November 2010 and April 2023. The primary objective was to determine whether history of C4d and/or DSA positivity could predict death, cardiac death, or retransplant. Secondary analyses included cardiac allograft dysfunction and cardiac allograft vasculopathy. Cox proportional hazards models were used for single predictor and multipredictor analyses. Results: A total of 6,033 EMBs from 519 HTx patients were reviewed for the study. There was no significant difference (p = 0.110) in all-cause mortality or cardiac retransplant between four groups: C4d+/DSA+, C4d+/DSA-, C4d-/DSA+, and C4d-/DSA-. The risk for cardiac mortality or retransplant was significantly higher in C4d+/DSA+ versus C4d-/DSA- patients (HR = 4.73; pc = 0.042) but not significantly different in C4d+/DSA- versus C4d-/DSA- patients (pc = 1.000). Similarly, the risk for cardiac allograft dysfunction was significantly higher in C4d+/DSA+ versus C4d-/DSA- patients (HR 3.26; pc = 0.001) but not significantly different in C4d+/DSA- versus C4d-/DSA- patients (pc = 1.000). Accounting for nonadherence, C4d/DSA status continued to predict cardiac allograft dysfunction but no longer predicted cardiac death or retransplant. Conclusions: Medically adherent C4d+/DSA+ HTx patients show significantly greater risk for cardiac allograft dysfunction but not cardiac mortality or retransplant. In contrast, C4d+/DSA- patients represent a new immunopathologic group with a clinical course similar to that of HTx patients without antibody mediated rejection.

Immunohistochemical Evaluation of C4d and C3d Markers in Bullous Pemphigoid as a Substitute for Direct Immunofluorescence Technique.

Background: There are several methods for the diagnosis of autoimmune bullous disease. Direct immunofluorescent (DIF) testing is an important diagnostic method in the diagnosis of immunobullous disease but requires skilled pathologist, fresh tissue and well-equipped laboratory to perform the procedure. The immunohistochemistry analysis of C4d and C3d is easily compared with other methods. This study was conducted to assess the value of immunohistochemistry (IHC) analysis for expressions of C3d and C4d in the diagnosis of bullous pemphigoid (BP). Aims and Objectives: This study was conducted to assess the value of immunohistochemistry (IHC) analysis for expressions of C3d and C4d in the diagnosis of bullous pemphigoid (BP). Materials and. Method: We applied C4d and C3d immunohistochemistry on formalin-fixed, paraffin-embedded tissue on 30 cases of bullous pemphigoid that was confirmed by direct immunofluorescence (DIF) evaluation as well as 16 cases in control group (12 cases of herpetiform dermatitis, 3 cases of linear IgA dermatosis and 3 cases of bullous lichen planus). Results: Mean and SD of age were 68.13 ± 14.00, female to male ratio was 1:3. In cases where both C3d and C4d staining were positive, the intensity of C3d staining was higher than C4d. Twenty-two cases showed C4d-positive staining in IHC study, such that in seven cases focal staining and in 15 cases diffuse staining were observed. Also 26 cases showed C3d-positive staining in IHC study such that in four cases focal staining and in 22 cases diffuse staining were observed. In cases with C3d-positive staining, there were 21 cases of deposition only on the bullous floor, one case on the bullous roof and four cases on the bullous roof and floor. In cases with C4d-positive staining, there were 17 cases of deposition on the bullous floor, two cases only on the bullous roof and three cases on the roof and floor. All control cases were negative for C3d and C4d staining in the dermoepidermal junction. For C3d immunohistochemical staining, sensitivity, specificity, positive predictive value and negative predictive value were 86.66%, 100%, 100% and 80%, respectively, and for C4d immunohistochemical staining, respectively, were 73.3%, 100%, 100% and 66.66%. Conclusion: The immunohistochemical specificity of C4d and C3d on tissue blocks is the same as that of direct immunofluorescence test on fresh tissue, but it is less sensitive, so positive results for C3d and C4d immunohistochemical staining on paraffin blocks can be used to confirm the diagnosis of bullous pemphigoid.

A portable liquid chromatography system based on a separation/detection chip module consisting of a replaceable ultraviolet-visible absorbance or contactless conductivity detection unit.

Recently, there has been a growing demand for miniaturized analytical instruments, including portable HPLC systems, that can enable rapid analysis in the field. This study aimed to develop chip-based separation/detection modules with replaceable detection units for constructing compact HPLC systems to minimize the dead volume. This module provides a tubing-free connection between the column and the detection unit. This study also built detection units for conductivity detection and ultraviolet-visible (UV-Vis) detection to cover a wide variety of inorganic and organic compounds. Furthermore, UV- and Vis-light-emitting diodes were employed for the absorbance detection unit. In addition, portable all-in-one HPLC systems and a handy HPLC system were constructed for ion chromatography and reversed-phase chromatography, demonstrating the successful separation and detection of inorganic ions and several organic compounds.

Diagnostic Dilemma in a Case of Necrotizing Lymphadenitis With Macrophage Activation Syndrome.

Necrotizing lymphadenitis is a histological diagnosis that can arise from various conditions, including lupus lymphadenitis (LL), Kikuchi disease (KD), and infectious causes. Distinguishing between Kikuchi disease and lupus lymphadenitis can be challenging in clinical practice. In this report, we present the clinical scenario of a young female patient with lymphadenopathy and elucidate the process through which we ultimately arrived at a diagnosis of systemic lupus erythematosus (SLE) with macrophage activation syndrome. This case underscores the significance of recognizing Kikuchi disease as a condition that can mimic lupus and sheds light on the distinguishing features of necrotizing lymphadenitis, with a particular focus on Kikuchi disease and lupus lymphadenitis.

Evidence for Alloimmune Sinusoidal Injury in De Novo Nodular Regenerative Hyperplasia After Liver Transplantation.

Posttransplant nodular regenerative hyperplasia (NRH) mostly remains unexplained. Microvascular injury due to antibody-mediated rejection (AMR) is suspected, but lack of donor specific antibody (DSA) testing makes it difficult to prove. Centered around a 1-year period of routine DSA testing, concomitant protocol, and indicated posttransplant liver biopsies (LB), recipients with NRH (n = 18) were compared with a matched control group (n = 36). All index, previous, and subsequent LB were reviewed. Both groups were similar in terms of demographics, timing of index LB, and DSA. In the index LB, the NRH group had higher sinusoidal C4d positivity (p = 0.029) and perisinusoidal fibrosis (p = 0.034), both independently associated with NRH (p = 0.038 and 0.050, respectively). Features of "possible" chronic AMR were detected in 28.5% of the NRH group without a known cause and 0% of the control group (p = 0.009). The NRH group had more preceding indicated LB with increased incidence of rejection and biliary obstruction pattern. In the follow-up histology, overall, sinusoidal and portal C4d positivity, sinusoidal microvasculitis, and perisinusoidal fibrosis were also higher (all p < 0.050). In conclusion, we provide evidence towards the hypothesis that some cases of posttransplant NRH are related to preceding active and persistent AMR. Large multicenter studies with protocol DSA testing are required to confirm.

A handheld contactless conductivity detector for monitoring the desalting of low-volume virus and cell samples.

Desalting of biosamples is crucial for analytical techniques intolerant to abundant salts. However, there is no simple tool to monitor the desalting of low-volume biosamples so far. Here we developed a handheld capacitively coupled contactless conductivity detector (hC4D) as a miniaturized device to measure the conductivity of 75 µL biosamples. Polyether-ether-ketone (PEEK) tubing was selected as the sample reservoir for sample loading via a pipette. Another pipetting of air pushed the sample solution out of the tubing to recollect the sample. Owing to the low sample consumption and easy sample recollection, hC4D is advantageous for testing expensive biosamples, such as viruses and cells. In addition, the whole process of sample injection, conductivity measurement, recollection, and calibration of conductivity can be completed within 1 min. To verify the feasibility of hC4D, we monitored the desalting progress of gel filtration (GF) of 200 µL blood samples, ultrafiltration (UF) of 300 µL virus samples, and dialysis of 7 mL cell samples. Three rounds of GF and UF completely removed the salts but led to poor sample recovery. In contrast, low concentrations of residual salts remained and better recovery was achieved after two rounds of GF and UF. We further utilized the hC4D to monitor the dialysis and tuned the salt concentration in the cell sample, such that we maintained the viability of cells in a low conductivity environment. These results indicated that hC4D is a promising tool for optimizing the desalting procedure of low-volume biosamples.

Renal C4d is a potential biomarker of disease activity and severity in pediatric lupus nephritis patients.

Background: Systemic lupus erythematosus (SLE), a multisystemic autoimmune disease, is very aggressive in pediatric-onset patients as they are prone to develop lupus nephritis (LN). Although renal C4d positivity is correlated with the activity of renal disease and SLE in adult-onset LN patients, available information for pediatric-onset patients is limited. Methods: To evaluate the potential diagnostic significance of renal C4d staining in pediatric LN patients, we retrospectively detected C4d staining by immunohistochemistry on renal biopsy specimens from 58 pediatric LN patients. The clinical and laboratory data at the time of the kidney biopsy and the renal disease activity of histological injury were analyzed according to the C4d staining status. Results: Glomerular C4d (G-C4d)-positive staining was detected in all 58 cases of LN. Patients with a G-C4d score of 2 displayed more severe proteinuria than those with a G-C4d score of 1 (24-h urinary protein: 3.40 ± 3.55 g vs. 1.36 ± 1.24 g, P < 0.05). Peritubular capillary C4d (PTC-C4d) positivity was found in 34 of 58 LN patients (58.62%). The PTC-C4d-positive patient groups (patients with a PTC-C4d score of 1 or 2) had higher serum creatinine and blood urea nitrogen levels as well as renal pathological activity index (AI) and SLE disease activity index (SLEDAI) scores; however, they had lower serum complement C3 and C4 levels compared to PTC-C4d-negative patients (P < 0.05). In addition, there was positive tubular basement membrane C4d (TBM-C4d) staining in 11 of 58 LN patients (18.96%), and a higher proportion of TBM-C4d-positive patients than TBM-C4d-negative patients (63.63% vs. 21.27%) had hypertension. Conclusion: Our study revealed that G-C4d, PTC-C4d, and TMB-C4d were positively correlated with proteinuria, disease activity and severity, and hypertension, respectively, in pediatric LN patients. These data suggest that renal C4d is a potential biomarker for disease activity and severity in pediatric LN patients, providing insights into the development of novel identification and therapeutic approaches for pediatric-onset SLE with LN.

Systemic evaluation of lymphocyte-bound C4d and immunoglobulins for diagnosis and activity monitoring of systemic lupus erythematosus.

OBJECTIVE: To investigate the role of lymphocyte-bound C4d (LB-C4d: T-C4d, B-C4d) and immunoglobulins (LB-Igs: T-IgG, T-IgM, B-κ and B-λ) in the diagnosis and monitoring of SLE. DESIGN & METHODS: The levels of C4d and Igs on peripheral lymphocytes were measured in 172 patients with SLE, 174 patients with other non-SLE inflammatory diseases and 100 healthy individuals. Immunobinding and blocking experiments were performed to characterize Igs from SLE patients to generate LB-C4d/Igs in vitro. Sixty-five patients with SLE were followed up longitudinally. Disease activity was assessed for each SLE patient. RESULTS: Patients with SLE had the highest median LB-C4d/Igs levels. LB-C4d had a significant but weak positive association with LB-Igs, with correlation coefficients ranging from 0.008 to 0.316. Anti-cardiolipin IgG and anti-ß2GP1 IgG, but not C3 and C4, were found to be closely associated with LB-C4d/Igs formation, with correlations as high as 0.337. Compared to anti-dsDNA, LB-C4d performed better in SLE diagnosis, while B-κ and B-λ performed better in disease activity monitoring. CONCLUSIONS: Both autoantibodies and receptors on lymphocytes contribute to LB-C4d/Igs formation. LB-C4d/Igs could be used as reliable indicators for SLE diagnosis and activity monitoring.

Diagnostic utility of C4d immunohistochemistry in membranous nephropathy.

OBJECTIVES: Membranous nephropathy (MN), also called membranous glomerulopathy, is one of the leading causes of nephrotic syndrome in adults which is defined by the presence of subepithelial immune complex deposits with a spectrum of changes in the glomerular basement membrane (GBM). It is known that C4d is a byproduct of the classic and lectin pathway. There is deposition of C4d noted in the cases of immune complex-mediated glomerulonephritis involving the classical/lectin pathway including MN. The main objective of this study is to assess the utility C4d as an immunohistochemical (IHC) stain in MN. MATERIALS: A total of 43 cases of MN (primary & secondary) were taken, and 39 cases of minimal change disease (MCD)/focal segmental glomerulosclerosis (FSGS) were used as the control group. All the relevant data were retrieved from the hospital database. C4d immunohistochemistry was performed in the cases as well as the control group. RESULTS: A diffuse continuous staining pattern in the glomeruli was observed in cases of primary MN whereas a discontinuous staining in the glomerulI favors a secondary MN. 26/29 cases of MCD showed positivity in the podocytes. Among the cases of FSGS, 7/10 cases showed positivity in the podocytes with 3 cases showing an associated mesangial blush pattern of staining. CONCLUSION: Very few studies are available demonstrating the importance of C4d IHC in MN. C4d IHC can be a useful adjunct for immunofluorescence, especially in cases of early MN.