Daily monitoring of viral load measured as SARS-CoV-2 antigen and RNA in blood, IL-6, CRP and complement C3d predicts outcome in patients hospitalized with COVID-19.

OBJECTIVES: We hypothesized that the amount of antigen produced in the body during a COVID-19 infection might differ between patients, and that maximum concentrations would predict the degree of both inflammation and outcome for patients. METHODS: Eighty-four hospitalized and SARS-CoV-2 PCR swab-positive patients, were followed with blood sampling every day until discharge or death. A total of 444 serial EDTA plasma samples were analyzed for a range of biomarkers: SARS-CoV-2 nuclear antigen and RNA concentration, complement activation as well as several inflammatory markers, and KL-6 as a lung marker. The patients were divided into outcome groups depending on need of respiratory support and death/survival. RESULTS: Circulating SARS-CoV-2 nuclear antigen levels were above the detection limit in blood in 65 out of 84 COVID-19 PCR swab-positive patients on day one of hospitalization, as was viral RNA in plasma in 30 out of 84. In all patients, complete antigen clearance was observed within 24 days. There were definite statistically significant differences between the groups depending on their biomarkers, showing that the concentrations of virus RNA and antigen were correlated to the inflammatory biomarker levels, respiratory treatment and death. CONCLUSIONS: Viral antigen is cleared in parallel with the virus RNA levels. The levels of antigens and SARS-CoV-2 RNA in the blood correlates with the level of IL-6, inflammation, respiratory failure and death. We propose that the antigens levels together with RNA in blood can be used to predict the severity of disease, outcome, and the clearance of the virus from the body.

Immunoglobulin and Complement Immunohistochemistry on Paraffin Sections in Autoimmune Bullous Diseases: A Systematic Review and Meta-analysis.

ABSTRACT: Immunohistochemistry (IHC) on formalin-fixed, paraffin-embedded tissue has been proposed as a potential tool in the diagnosis of autoimmune bullous diseases (AIBDs) in lieu of standard direct immunofluorescence (DIF) microscopy. To comprehensively determine the diagnostic accuracy of immunoglobulin and complement IHC for diagnosis of AIBDs, we conducted a systematic review and multivariate Bayesian model-based meta-analysis of the literature. Quality and heterogeneity assessment of studies was performed using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) checklist and the I2 index, respectively. Electronic searches using PubMed from April 1964 to July 2020 identified 14 articles meeting predetermined inclusion and exclusion criteria. Median sensitivities with 95% credible intervals in pemphigus and pemphigoid were 0.24 (0.01-0.89) and 0.22 (0.02-0.77) with immunoglobulin G (IgG), 0.77 (0.39-0.95) and 0.25 (0.02-0.85) with IgG4, 0.11 (0.02-0.32) and 0.86 (0.56-0.98) with C3d, and 0.84 (0.56-0.97) and 0.75 (0.37-0.94) with C4d, respectively. Specificities were 1.00 (0.00-1.00) with IgG, 0.98 (0.89-1.00) with IgG4, 0.99 (0.97-1.00) with C3d, and 0.99 (0.97-1.00) with C4d. The risk of bias and heterogeneity among studies was a serious problem, decreasing the level of evidence. Our work suggests that, in selected cases, paraffin-based IHC may be a helpful procedure to screen for AIBDs, especially when specialized laboratories and/or biopsy specimens for DIF do not exist. Nevertheless, more studies with a refined quality design are needed to explore the true usefulness of this diagnostic method in AIBDs.

Genetic and environmental risk factors for extramacular drusen.

PURPOSE: To analyze risk factors for extramacular drusen (EMD) in patients with age-related macular degeneration (AMD) and healthy control individuals. METHODS: This case-control study included 1,520 patients from the prospective multicenter European Genetic Database (EUGENDA). Color fundus photographs and optical coherence tomography scans were evaluated for the presence of AMD and EMD. EMD was considered present if ten or fewer drusen including at least one intermediate-sized drusen were detected outside the macula. Association of EMD was evaluated with various genetic and non-genetic risk factors (31 single nucleotide polymorphisms, systemic complement activation, smoking, cardiovascular factors, and sunlight exposure) using logistic regression models adjusted for age, gender, and AMD. RESULTS: EMD was found in 608 subjects (40%) and AMD in 763 (50%) of 1,520 participants. EMD was strongly associated with AMD (p = 2.83 × 10-63, odds ratio [OR] 7.63). After adjustment for AMD, age (p = 0.06, OR 1.02), female gender (p = 3.34 × 10-24, OR 4.44), history of sunlight exposure ≥ 8 h /day (p = 0.0004, OR 1.99), serum complement activation (p = 0.004, OR 1.61), and polymorphisms in ARMS2 (p = 0.00016, OR 1.43) and CFI (p = 0.043, OR 1.20) were identified as risk factors for EMD. The final prediction model including these variants showed an area under the curve of 0.820. CONCLUSIONS: The comprehensive analysis of various risk factors revealed a common genetic and pathological pathway of EMD with AMD. Future longitudinal studies are needed to evaluate the role of EMD in otherwise healthy subjects as an expanded phenotype of AMD.

Antibacterial Fusion Proteins Enhance Moraxella catarrhalis Killing.

Moraxella catarrhalis is a human-specific commensal of the respiratory tract and an opportunistic pathogen. It is one of the leading cause of otitis media in children and of acute exacerbations in patients with chronic obstructive pulmonary disease, resulting in significant morbidity and economic burden. Vaccines and new immunotherapeutic strategies to treat this emerging pathogen are needed. Complement is a key component of innate immunity that mediates the detection, response, and subsequent elimination of invading pathogens. Many pathogens including M. catarrhalis have evolved complement evasion mechanisms, which include the binding of human complement inhibitors such as C4b-binding protein (C4BP) and Factor H (FH). Inhibiting C4BP and FH acquisition by M. catarrhalis may provide a novel therapeutic avenue to treat infections. To achieve this, we created two chimeric proteins that combined the Moraxella-binding domains of C4BP and FH fused to human immunoglobulin Fcs: C4BP domains 1 and 2 and FH domains 6 and 7 fused to IgM and IgG Fc, respectively. As expected, FH6-7/IgG displaced FH from the bacterial surface while simultaneously activating complement via Fc-C1q interactions, together increasing pathogen elimination. C4BP1-2/IgM also increased serum killing of the bacteria through enhanced complement deposition, but did not displace C4BP from the surface of M. catarrhalis. These Fc fusion proteins could act as anti-infective immunotherapies. Many microbes bind the complement inhibitors C4BP and FH through the same domains as M. catarrhalis, therefore these Fc fusion proteins may be promising candidates as adjunctive therapy against many different drug-resistant pathogens.

Urinary C3d is elevated in patients with active Lupus nephritis and a fall in its level after 3 months predicts response at 6 months on follow up.

INTRODUCTION: Complement activation is central to the pathogenesis of lupus nephritis (LN). Low serum complement C3 and C4, are traditionally used as markers of lupus disease activity in general and LN in particular. In this study we prospectively measured plasma and urine C3d and C4d, degradation products of C3 and C4 corrected to creatinine in a cohort of biopsy proven LN in a longitudinal fashion for its correlation with disease activity. METHODS: Twenty eight biopsy proven active lupus nephritis (AN) were recruited along with four inactive nephritis (IN) and 10 healthy controls (HC). Plasma and urine were collected at baseline, prior to induction treatment and 3 months later. Clinical measures of disease activity, Systemic lupus erythematosus disease activity index 2000 (SLEDAI 2K), renal SLEDAI, serum C3, C4 and antibodies to ds DNA, urine protein and creatinine excretion (UP/UC) were collected. Plasma and urine C3d and C4d were measured using ELISA and normalized to spot urine creatinine value. RESULTS: Twenty eight AN of median age of 26.5 (20-31.50) years and disease duration of 3 (0.7-5) years were enrolled. The median urinary C3d/creatinine before treatment was 388.20 (48.98-1296) ng/mg which fell significantly to 62.69 (28.04-502.4) ng/mg at 3 months followup (p-0.01). The baseline values for the active renal disease was significantly different from IN group (9.9 (4.5-46.53 ng/mg) p-0.00). Treatment responders (partial and complete) at 6 months showed a significant fall in urinary C3d at 3 months whereas non responders had a non significant change in value. There was a significant correlation of urine C3d/creatinine with SLEDAI2K (r-0.433, p-0.00), renal SLEDAI (r-0.356, p-0.00), UP/UC ratio (r-0.489, p-<0.0001) but no significant correlation with C3 or C4. There was a significant fall in the median values of plasma C3d from 791.1 (516.0.00-1550.43) µg/ml to 338.52 (211.35-525.82) (p-0.00) µg/ml at the end of 3 months. The values showed a significant correlation with SLEDAI 2K, renal SLEDAI, UP/UC along with a significant negative correlation with C3 and C4. CONCLUSION: Urinary C3d/creatinine levels and plasma C3d levels can be used as biomarker of disease activity and treatment response.

Complement Activation Levels Are Related to Disease Stage in AMD.

Purpose: To study the levels of complement activation in different disease stages of AMD and the influence of genetic polymorphisms in complement genes. Methods: We included 797 patients with AMD and 945 controls from the European Genetic Database. Patients were grouped into five AMD stages: early AMD, intermediate AMD, central geographic atrophy, active choroidal neovascularization or inactive choroidal neovascularization. Differences in complement activation, as defined by the systemic C3d/C3 ratio, between AMD stages were evaluated using general linear modeling. In addition, we evaluated the influence of 18 genetic AMD polymorphisms in complement genes and their effect on complement activation. Differences in complement activation between stages were evaluated stratifying by complement associated haplotypes. Results: Complement activation levels differed significantly between AMD disease stages. As compared with controls, the C3d/C3 ratio was higher in patients with intermediate AMD (P < 0.001) and central geographic atrophy (P = 0.001). Two polymorphisms in CFH (rs10922109 and rs570618) and one in CFB (rs116503776) were significantly associated with complement activation. The association between AMD disease stage and complement activation was more pronounced in patients with haplotypes associated with the highest complement activation. Conclusions: In general, consecutive AMD disease stages showed increasing levels of complement activation, especially in individuals with a genetic burden in complement genes. These findings contribute to the discussion on the pathogenesis of AMD in relation to complement activation and might suggest refinement in patient selection and the optimum window of treatment with complement inhibitors. Prospective studies are needed to confirm these results.

Utility of immunohistochemistry with C3d in C3 glomerulopathy.

C3-dominance by immunofluorescence is a defining feature in the diagnosis of C3 glomerulopathy. Most pathologists stain for C3c, which has been reported as a trace/negative even in otherwise clear-cut cases of dense deposit disease. We investigated the usefulness of C3d immunohistochemistry in biopsies with C3 glomerulopathy as an ancillary diagnostic tool. All biopsies from patients diagnosed with C3 glomerulopathy in the period January 2005 to June 2017 in the Erasmus MC, Rotterdam were included (n = 14; 10 C3 glomerulonephritis, 4 dense deposit disease). The staining pattern of C3d and C4d by immunohistochemistry was analyzed. As controls, biopsies from patients with immune complex membranoproliferative glomerulonephritis (n = 2), infection-associated glomerulonephritis (n = 6), pauci-immune crescentic glomerulonephritis (n = 7), tubulointerstitial nephritis (n = 7) and chronic-active antibody-mediated rejection (n = 9) were included. All 14 biopsies with C3 glomerulopathy showed a C3d score of ≥2, including two clear-cut biopsies with C3 glomerulopathy originally showing a trace/negative staining for C3c. In the control group, a C3d score ≥2 was observed in 11 biopsies (35%; 2 with immune complex membranoproliferative glomerulonephritis (100%), 6 with infection-associated glomerulonephritis (100%), 1 with pauci-immune crescentic glomerulonephritis (14%), 1 with tubulointerstitial nephritis (14%) and 1 with chronic-active antibody-mediated rejection (11%)). C4d was positive in 71% of the biopsies with C3 glomerulopathy (10/14). In conclusion, C3d immunohistochemistry is a valuable tool in the diagnosis of C3 glomerulopathy, especially in cases in which C3c immunofluorescence shows a trace/negative. We recommend the use of C3d in addition to C3c in cases suspicious for C3 glomerulopathy.

Differential immunoglobulin and complement levels in leprosy prior to development of reversal reaction and erythema nodosum leprosum.

BACKGROUND: Leprosy is a treatable infectious disease caused by Mycobacterium leprae. However, there is additional morbidity from leprosy-associated pathologic immune reactions, reversal reaction (RR) and erythema nodosum leprosum (ENL), which occur in 1 in 3 people with leprosy, even with effective treatment of M. leprae. There is currently no predictive marker in use to indicate which people with leprosy will develop these debilitating immune reactions. Our peripheral blood mononuclear cell (PBMC) transcriptome analysis revealed that activation of the classical complement pathway is common to both RR and ENL. Additionally, differential expression of immunoglobulin receptors and B cell receptors during RR and ENL support a role for the antibody-mediated immune response during both RR and ENL. In this study, we investigated B-cell immunophenotypes, total and M. leprae-specific antibodies, and complement levels in leprosy patients with and without RR or ENL. The objective was to determine the role of these immune mediators in pathogenesis and assess their potential as biomarkers of risk for immune reactions in people with leprosy. METHODOLOGY/FINDINGS: We followed newly diagnosed leprosy cases (n = 96) for two years for development of RR or ENL. They were compared with active RR (n = 35), active ENL (n = 29), and healthy household contacts (n = 14). People with leprosy who subsequently developed ENL had increased IgM, IgG1, and C3d-associated immune complexes with decreased complement 4 (C4) at leprosy diagnosis. People who developed RR also had decreased C4 at leprosy diagnosis. Additionally, elevated anti-M. leprae antibody levels were associated with subsequent RR or ENL. CONCLUSIONS: Differential co-receptor expression and immunoglobulin levels before and during immune reactions intimate a central role for humoral immunity in RR and ENL. Decreased C4 and elevated anti-M. leprae antibodies in people with new diagnosis of leprosy may be risk factors for subsequent development of leprosy immune reactions.

Acute Complement Inhibition Potentiates Neurorehabilitation and Enhances tPA-Mediated Neuroprotection.

Because complement activation in the subacute or chronic phase after stroke was recently shown to stimulate neural plasticity, we investigated how complement activation and complement inhibition in the acute phase after murine stroke interacts with subsequent rehabilitation therapy to modulate neuroinflammation and neural remodeling. We additionally investigated how complement and complement inhibition interacts with tissue plasminogen activator (tPA), the other standard of care therapy for stroke, and a U.S. Food and Drug Administration preclinical requirement for translation of an experimental stroke therapy. CR2fH, an injury site-targeted inhibitor of the alternative complement pathway, significantly reduced infarct volume, hemorrhagic transformation, and mortality and significantly improved long-term motor and cognitive performance when administered 1.5 or 24 h after middle cerebral artery occlusion. CR2fH interrupted a poststroke inflammatory process and significantly reduced inflammatory cytokine release, microglial activation, and astrocytosis. Rehabilitation alone showed mild anti-inflammatory effects, including reduced complement activation, but only improved cognitive recovery. CR2fH combined with rehabilitation significantly potentiated cognitive and motor recovery compared with either intervention alone and was associated with higher growth factor release and enhanced rehabilitation-induced neuroblast migration and axonal remodeling. Similar outcomes were seen in adult, aged, and female mice. Using a microembolic model, CR2fH administered in combination with acute tPA therapy improved overall survival and enhanced the neuroprotective effects of tPA, extending the treatment window for tPA therapy. A human counterpart of CR2fH has been shown to be safe and nonimmunogenic in humans and we have demonstrated robust deposition of C3d, the CR2fH targeting epitope, in ischemic human brains after stroke.SIGNIFICANCE STATEMENT Complement inhibition is a potential therapeutic approach for stroke, but it is not known how complement inhibition would interact with current standards of care. We show that, after murine ischemic stroke, rehabilitation alone induced mild anti-inflammatory effects and improved cognitive, but not motor recovery. However, brain-targeted and specific inhibition of the alternative complement pathway, when combined with rehabilitation, significantly potentiated cognitive and motor recovery compared with either intervention alone via mechanisms involving neuroregeneration and enhanced brain remodeling. Further, inhibiting the alternative pathway of complement significantly enhanced the neuroprotective effects of thrombolytic therapy and markedly expanded the therapeutic window for thrombolytic therapy.

Understanding the Correlation Between DSA, Complement Activation, and Antibody-Mediated Rejection in Heart Transplant Recipients.

BACKGROUND: Donor-specific HLA antibodies (DSA) are associated with increased rates of rejection and of graft failure in cardiac transplantation. The goal of this study was to determine the association of preformed and posttransplant development of newly detected DSA (ndDSA) with antibody-mediated rejection (AMR) and characterize the clinical relevance of complement-activating DSA in heart allograft recipients. METHODS: The study included 128 adult and 48 pediatric heart transplant patients transplanted between 2010 and 2013. Routine posttransplant HLA antibody testing was performed by IgG single-antigen bead test. The C3d single-antigen bead assay was used to identify complement-activating antibodies. Rejection was diagnosed using International Society for Heart and Lung Transplantation criteria. RESULTS: In this study, 22 patients were transplanted with preexisting DSA, and 43 patients developed ndDSA posttransplant. Pretransplant (P < 0.05) and posttransplant (P < 0.001) ndDSA were associated with higher incidence of AMR. Patients with C3d + DSA had significantly higher incidence of AMR compared with patients with no DSA (P < 0.001) or patients with C3d-DSA (P = 0.02). Nine (36%) of 25 patients with AMR developed transplant coronary artery disease compared with 17 (15.9%) of 107 patients without AMR (P < 0.05). Among the 47 patients who received ventricular assistant device (VAD), 7 of 9 VAD+ patients with preformed DSA experienced AMR compared with 7 of 38 VAD+ patients without preformed DSA, indicating presensitization to donor HLA significantly increased the risk of AMR (P < 0.01). CONCLUSIONS: Preformed and posttransplant ndDSA were associated with AMR. C3d + DSA correlates with complement deposition on the graft and higher risk of AMR which may permit the application of personalized immunotherapy targeting the complement pathway.

Immunohistochemical diagnosis of mucous membrane pemphigoid.

BACKGROUND: Mucous membrane pemphigoid (MMP) is an autoimmune subepithelial blistering disease with predominant involvement of mucosal surfaces. It is usually diagnosed by direct immunofluorescence microscopy of frozen biopsies, demonstrating linear deposits of complement, IgG or IgA along the basement membrane. The aim of this study was to investigate the utility of immunohistochemistry on formalin-fixed, paraffin-embedded tissue biopsies for the diagnosis of MMP and to compare its sensitivity to that of direct immunofluorescence microscopy. METHODS: We examined 50 biopsies from 34 patients with immunologically confirmed MMP by immunohistochemistry for C3d, C4d, IgG and IgA. RESULTS: Linear deposits of C3d were detected in 46% of biopsies, and 53% of patients had at least one biopsy positive for C3d. Linear deposits of C4d were detected in 52% of biopsies and 59% of patients had at least one biopsy positive for C4d. Overall, 56% of biopsies and 68% of patients were positive by either C3d or C4d or both stainings. The sensitivity of either staining in mucosal biopsies was lower than in skin samples. Basement membrane deposits of IgG or IgA could not be detected in any biopsy. CONCLUSIONS: Our findings demonstrate that immunohistochemistry for C3d or C4d is a helpful screening procedure for cases of suspected MMP where frozen tissue is not readily available. Negative findings, however, do not exclude a possible diagnosis of MMP and should prompt an additional biopsy for direct immunofluorescence studies. Immunohistochemical detection of IgG or IgA cannot yet be used for the diagnosis of MMP.

Donor-specific HLA antibody-mediated complement activation is a significant indicator of antibody-mediated rejection and poor long-term graft outcome during lung transplantation: a single center cohort study.

Complement-mediated allograft injury, elicited by donor-specific HLA antibodies (DSA), is a defining pathophysiological characteristic of allograft damage. We aimed to study DSA-induced complement activation as a diagnostic marker of antibody-mediated rejection (AMR) and a risk stratification tool for graft loss in the context of lung transplantation (LT). We identified 38 DSA-positive patients whose serum samples were submitted for C3d deposition testing via the C3d assay. Among these 38 patients, 15 had AMR (DSAPos AMRPos ). Results were reported for each patient as the C3d ratio for each DSA, the immunodominant DSA, and the C3d ratio for all DSA present in a sample (C3d ratioSUM ). DSAPos AMRPos patients had higher C3d ratioSUM values (58.66 (-1.32 to 118.6) vs. 1.52 (0.30 to 2.74), P = 0.0016) and increased immunodominant C3d ratios (41.87 (1.72 to 82.02) vs. 0.69 (0.21 to 1.19), P = 0.001) when compared with DSAPos AMRNeg patients. Specificity and calculated positive predictive value of the immunodominant C3d ratio and BCMsum tests for AMR diagnosis were both 100% (CI = 17.4-100) in this cohort. Worst graft survival was associated with both immunodominant C3d ratio ≥4 or C3d ratioSUM ≥10 or BCMsum >7000, suggesting that the antibody composition and/or strength are the principal determinants of an HLA DSA's capacity to activate complement.

Tubular basement membrane immune complex deposition is associated with activity and progression of lupus nephritis: a large multicenter Chinese study.

Tubulointerstitial injury is found frequently in lupus nephritis. Immune complex deposits can occur in the tubular basement membranes (TBMs), although its significance in lupus nephritis patients remains unclear. This study assessed the clinical and prognostic features of lupus nephritis patients with TBM deposits in a large Chinese multicenter cohort. Complete data were collected from 195 patients with renal biopsy-proven lupus nephritis diagnosed in the Peking University First Hospital as the discovery cohort. A total of 102 lupus nephritis patients were enrolled from another four centers as the validation cohort. The status of TBM deposits was retrospectively assessed using electron microscopy, and the associations of the deposits with clinical data, pathological characteristics and renal outcomes were further analyzed. The percentage of positive TBM deposits was nearly 30% in the lupus nephritis patients. Using immuno-gold labeling, we found that 10/10 patients were positive for IgG, 7/10 were C3d positive, 6/10 were C1q positive, and 1/10 were C4d positive. Patients with TBM deposits presented with more active features, including a higher SLEDAI score (SLE Disease Activity Index) ( p < 0.001), higher serum creatinine level ( p = 0.001) and lower serum C3 level ( p < 0.001). These patients also presented with higher scores for most renal pathological indices, including the total activity indices score ( p < 0.001) and total chronicity indices score ( p = 0.001). TBM deposits affected renal outcomes in the univariate Cox hazards regression analysis (HR = 4.2, 95% CI = 1.3-14.3, p = 0.02). In conclusion, TBM deposits were common in lupus nephritis patients and correlated closely with the clinical disease activity and renal outcome.

The clinical implications of the unique glomerular complement deposition pattern in transplant glomerulopathy.

The etiology and treatment of transplant glomerulopathy (TG) is not clear. TG is associated with donor-specific antibodies but the lack of C4d deposition in the peritubular capillaries (ptc-C4d) in some cases has caused the role of complement in the pathogenesis of TG to be debated. There is however, little information on C4d deposition in the glomerulus itself. We retrieved random frozen sections from 25 cases with well-established TG by light microscopy (LM) and 25 cases without TG as controls and reviewed the LM and immunofluorescence (nine biopsies were excluded due to inadequate samples). Glomerular complement deposition was assessed in all included biopsies. Glomerular C3d and C4d deposition occurred in a distinct pattern in all TG biopsies: segmental or global double linear staining of the glomerular capillary wall in 23 (100%). This pattern was not present in any NON-TG biopsies. The distinct glomerular complement deposition patterns in all TG cases are suggestive that TG is a proximal complement-mediated process and therapies should focus on proximal complement inhibition.

[Expression of C3d in normal human liver tissues with non-immunologic osmostic mechanism].

Objective: To observe the deposition of complement C3d at different development stages in human normal organs and tissues, and investigate the significance of its deposition. Methods: Using immunohistochemical methods, the deposition of C3d was detected at different development stages of 60 normal human organs and tissue specimens and double staining was performed in some specimens. Ninty-five cases of other organs or tissues were collected as control group. Results: In 50 of 60 livers, it was observed the deposition of C3d in Glisson's capsule and periportal sheath, with irregular linear network-like disposition surrounding the portal sheath. In different age groups, the expression of C3d was more beyond the 20 year-old group than 3 to 20 year-old group. There wasn't any expression of C3d under 3-year-old group. Under the immuning electron micrograph, C3d depositing at the Glisson's capsule was observed, without immuning compounding. Thirty in 40 spleens, deposition of C3d in capsules, arteries of lymphatic sheath, follicles in the spleen was observed. Conclusions: The deposition of C3d in Glisson's capsule, splenic trabeculae, fibrous sheath, endarterium of liver and spleen arterioles, within normal human tissues from patients elder than 3 years, are osmosis/immunogenic deposition. The deposition of C3d is a normal physiological phenomenon, and treatment of the deposition of C3d should be avoided, as it is an immune complex or immuning reaction phenomenon.

Computer-assisted topological analysis of renal allograft inflammation adds to risk evaluation at diagnosis of humoral rejection.

Antibody-mediated rejection is associated with heterogeneous kidney allograft outcomes. Accurate evaluation of risk for graft loss at time of diagnosis is necessary to offer personalized treatment. In contrast with serological and molecular assessment, morpho-histological evaluation of antibody-mediated rejection lesions has not significantly evolved. This relies on Banff classifications designed to be of diagnostic discriminatory power rather than prognostic and face quantitative and qualitative limitations. Here we developed a method of Computer-assisted Analysis of Graft Inflammation (CAGI) to improve the classification of allograft inflammation. Digitization of immunostained biopsy sections, image processing and algorithm-driven analysis allowed quantification of macrophages, T cells, B cells, and granulocytes per unit surface of interstitium, capillaries or glomeruli. CAGI was performed on biopsy specimens of 52 patients with extensively phenotyped antibody-mediated rejection. Macrophage numbers in capillaries and interstitium, but not Banff scores or the amount of other immune cell subsets, correlated with donor-specific antibody (DSA) mean fluorescence intensity and DSA-C3d status. The quantity of macrophages in the interstitium and DSA-C3d status were the only independent predictors for significant allograft loss at the time of antibody-mediated rejection diagnosis (hazard ratio 3.71 and 2.34, respectively). A significant strategy integrating the DSA-C3d assay and the quantification of interstitial macrophages allowed identification of three groups with distinct renal prognosis: DSA-C3d-, DSA-C3d+/macrophages-low and DSAC3d+/macrophages-high. Thus, CAGI brings a missing piece to the antibody-mediated rejection puzzle by identifying morpho-histological processes that bridge in vitro parameters of DSA pathogenicity and graft loss. Hence, this approach could be useful in future integrated strategies of risk evaluation.

Can immunohistochemistry replace immunofluorescence in diagnosis of skin bullous diseases?

Autoimmune bullous diseases are distressing and sometimes risky bullous dermatoses characterized by the presence of antibodies focused against disease-specific target antigens. Recognition of these antibodies using immunofluorescence is used to be the only sure diagnostic method after reviewing the routine histopathological section. Because of many causes that make the using of immunofluorescence difficult, we tried to evaluate the role of immunohistochemistry in diagnosis of these bullous skin diseases; 40 pemphigus cases (30 pemphigus vulgaris and 10 pemphigus foliaceus) and 37 non-pemphigus cases (35 vesiculobullous skin diseases and 2 normal skin). Skin biopsy was obtained for histopathological diagnosis, immunofluorescence study, and immune-histochemical studying for IgG4 and C3d expression. IgG4 was positive in almost all cases of pemphigus vulgaris and most of pemphigus foliaceus and bullous pemphigoides, while all other diseases were negative. C3d expression was positive in almost all bullous pemphigoides and pemphigus gestationis cases, while it was negative in almost all other cases. Sensitivity and specificity of both markers increase by using them in combination in diagnosis of such bullous diseases. IgG4 and C3d immunohistochemistry could replace DIF in almost all of our cases, so before doing DIF, reliable immunohistochemical detection of IgG4 and C3d on formalin-fixed tissue is advised to be done.

Glomerular C3d as a novel prognostic marker for renal vasculitis.

Pauci-immune necrotizing crescentic glomerulonephritis is the histologic substrate of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis. Several studies in animal models have demonstrated the crucial role of complement activation in the pathogenesis of ANCA-associated vasculitis, but only small series have analyzed the prognostic implications of complement glomerular deposits. This study aimed to assess the clinical and prognostic implications of C3d- and C4d-positive glomerular staining in renal vasculitis. Eighty-five patients with a diagnosis of pauci-immune necrotizing crescentic glomerulonephritis were included in the study. C3d and C4d were analyzed by immunohistochemical staining using a polyclonal antibody. The primary predictors were glomerular C3d- and C4d-positive staining. The primary end point was the cumulative percentage of patients who developed end-stage renal disease. Glomerular staining for C3d and C4d was observed in 42 (49.4%) of 85 biopsies and 38 (44.7%) of 85 biopsies, respectively. C3d-positive staining was associated with the severity of renal impairment and with a lower response rate to treatment (P=.003 and P=.04, respectively). Renal survival at 2 and 5 years was 60.9% and 51.8% in C3d-positive patients compared with 87.7% and 78.9% in C3d-negative patients (P=.04). C4d-positive staining did not show any impact in renal outcome. When adjusted by renal function and other histologic parameters, C3d staining remained as an independent predictor for renal survival (hazard ratio, 2.5; 95% confidence interval, 1.1-5.7; P=.03). Therefore, this study demonstrates that C3d-positive glomerular staining is an independent risk factor for the development of end-stage renal disease in ANCA-associated renal vasculitis.

Analysis of Risk Alleles and Complement Activation Levels in Familial and Non-Familial Age-Related Macular Degeneration.

AIMS: Age-related macular degeneration (AMD) is a multifactorial disease, in which complement-mediated inflammation plays a pivotal role. A positive family history is an important risk factor for developing AMD. Certain lifestyle factors are shown to be significantly associated with AMD in non-familial cases, but not in familial cases. This study aimed to investigate whether the contribution of common genetic variants and complement activation levels differs between familial and sporadic cases with AMD. METHODS AND RESULTS: 1216 AMD patients (281 familial and 935 sporadic) and 1043 controls (143 unaffected members with a family history of AMD and 900 unrelated controls without a family history of AMD) were included in this study. Ophthalmic examinations were performed, and lifestyle and family history were documented with a questionnaire. Nine single nucleotide polymorphisms (SNPs) known to be associated with AMD were genotyped, and serum concentrations of complement components C3 and C3d were measured. Associations were assessed in familial and sporadic individuals. The association with risk alleles of the age-related maculopathy susceptibility 2 (ARMS2) gene was significantly stronger in sporadic AMD patients compared to familial cases (p = 0.017 for all AMD stages and p = 0.003 for advanced AMD, respectively). ARMS2 risk alleles had the largest effect in sporadic cases but were not significantly associated with AMD in densely affected families. The C3d/C3 ratio was a significant risk factor for AMD in sporadic cases and may also be associated with familial cases. In patients with a densely affected family this effect was particularly strong with ORs of 5.37 and 4.99 for all AMD and advanced AMD respectively. CONCLUSION: This study suggests that in familial AMD patients, the common genetic risk variant in ARMS2 is less important compared to sporadic AMD. In contrast, factors leading to increased complement activation appear to play a larger role in patients with a positive family history compared to sporadic patients. A better understanding of the different contributions of risk factors in familial compared to non-familial AMD will aid the development of reliable prediction models for AMD, and may provide individuals with more accurate information regarding their individual risk for AMD. This information is especially important for individuals who have a positive family history for AMD.