C3d-Targeted factor H inhibits tissue complement in disease models and reduces glomerular injury without affecting circulating complement.

Complement-mediated diseases can be treated using systemic inhibitors. However, complement components are abundant in circulation, affecting systemic inhibitors' exposure and efficacy. Furthermore, because of complement's essential role in immunity, systemic treatments raise infection risk in patients. To address these challenges, we developed antibody fusion proteins combining the alternative-pathway complement inhibitor factor H (fH1-5) with an anti-C3d monoclonal antibody (C3d-mAb-2fH). Because C3d is deposited at sites of complement activity, this molecule localizes to tissue complement while minimizing circulating complement engagement. These fusion proteins bind to deposited complement in diseased human skin sections and localize to activated complement in a primate skin injury model. We further explored the pharmacology of C3d-mAb-2fH proteins in rodent models with robust tissue complement activation. Doses of C3d-mAb-2fH >1 mg/kg achieved >75% tissue complement inhibition in mouse and rat injury models while avoiding circulating complement blockade. Glomerular-specific complement inhibition reduced proteinuria and preserved podocyte foot-process architecture in rat membranous nephropathy, indicating disease-modifying efficacy. These data indicate that targeting local tissue complement results in durable and efficacious complement blockade in skin and kidney while avoiding systemic inhibition, suggesting broad applicability of this approach in treating a range of complement-mediated diseases.

Identification and structural analysis of dimeric chicken complement component 3d and its binding with chicken complement receptor 2.

Complement component 3d (C3d), the final cleavage product of complement component C3, interacts with CR2 and thus plays a crucial role in linking the innate and adaptive immune systems. Additionally, human C3d executes various functions in its dimeric form, which is more effective than its monomeric form. In this study, we aimed to explored whether chicken C3d (chC3d) exhibits similar characteristics, namely dimerization and binding of dimeric chC3d to chicken CR2 (chCR2). We investigated the interaction and co-localization of chC3d with itself using coimmunoprecipitation and confocal laser scanning microscopy, respectively. Then, dimeric chC3d was detected using native polyacrylamide gel electrophoresis and western blotting, and its equilibrium dissociation constant KD (827 nM) was determined using surface plasmon resonance. Finally, the interaction modes of dimeric chC3d were identified using molecular docking simulations, which revealed that dimeric chC3d could crosslink with chCR2 receptor. Overall, our findings will facilitate future explorations of the chicken complement system.

Complement C3d/C4d Deposition on Platelets Correlates with 2'-O-Methoxyethyl Antisense Oligonucleotide-Induced Thrombocytopenia in Monkeys.

2'-O-Methoxyethyl antisense oligonucleotide (2'-MOE ASO)-induced severe thrombocytopenia (TCP) [platelet (PLT) count <50 K/µL] was observed in the Asian-sourced cynomolgus monkeys with low incidence (2%-4% at doses >5 mg/kg/week). The potential mechanisms for TCP were studied using the Mauritian-sourced cynomolgus monkeys, which were shown to be more susceptible to ASO-induced TCP, along with the Asian-sourced animals. ISIS 405879, a 2'-MOE ASO, induced severe TCP (PLT <50 K/µL) in seven of nine Mauritian-sourced monkeys but not in the Asian-sourced monkeys after 16 weeks of treatment at 40 mg/kg/week. Marked increases in PLT-bound C3d/C4d were detected in all thrombocytopenic Mauritian-sourced monkeys but not in the unaffected Mauritian- or Asian-sourced monkeys, suggesting increased PLT clearance due to complement deposition on the PLTs. However, this effect was independent of the ASO-mediated fluid-phase alternative complement activation. A correlation was also observed between serum antiglycoprotein (GP) IIb/IIIa immunoglobulin G (IgG) and PLT reduction. In addition, increases in total serum IgM, anti-PLT IgM, and anti-PLT factor 4 IgM levels were observed in monkeys from both sources but were more evident in the Mauritian-sourced monkeys. These data suggest an enhanced innate immune cell activation to ISIS 405879, leading to increased PLT destruction through complement fixation on the PLTs or PLT crossreacting polyclonal antibody production.

Identification and Characterization of chCR2, a Protein That Binds Chicken Complement Component 3d.

Complement receptor type 2 (CR2) is an important membrane molecule expressed on B cells and follicular dendritic cells. Human CR2 has been shown to play a critical role in bridging the innate complement-mediated immune response with adaptive immunity by binding complement component 3d (C3d). However, the chicken CR2 (chCR2) gene has not been identified or characterized. In this study, unannotated genes that contain short consensus repeat (SCR) domains were analyzed based on RNA sequencing data for chicken bursa lymphocytes, and a gene with >80% homology to CR2 from other bird species was obtained. The gene consisted of 370 aa and was much smaller than the human CR2 gene because 10-11 SCRs were missing. The gene was then demonstrated as a chCR2 that exhibited high binding activity to chicken C3d. Further studies revealed that chCR2 interacts with chicken C3d through a binding site in its SCR1-4 region. An anti-chCR2 mAb that recognizes the epitope 258CKEISCVFPEVQ269 was prepared. Based on the anti-chCR2 mAb, the flow cytometry and confocal laser scanning microscopy experiments confirmed that chCR2 was expressed on the surface of bursal B lymphocytes and DT40 cells. Immunohistochemistry and quantitative PCR analyses further indicated that chCR2 is predominantly expressed in the spleen, bursa, and thymus, as well as in PBLs. Additionally, the expression of chCR2 varied according to the infectious bursal disease virus infection status. Collectively, this study identified and characterized chCR2 as a distinct immunological marker in chicken B cells.

Noninvasive Detection of iC3b/C3d Deposits in the Kidney Using a Novel Bioluminescent Imaging Probe.

SIGNIFICANCE STATEMENT: Histologic quantification of complement C3 deposits in kidney biopsies provides prognostic information in patients with glomerulonephritis. Unfortunately, kidney biopsies are invasive procedures that cannot be performed regularly and only provide a snapshot of a small portion of one kidney at the time of sampling. We have developed a method to noninvasively detect specific C3 fragment deposition throughout both kidneys, using a monoclonal antibody targeting tissue-bound iC3b/C3d linked to a bioluminescent resonance energy transfer construct that emits near-infrared light. In a mouse model of glomerulonephritis, the probe detected iC3b/C3d in kidneys of live mice by bioluminescent imaging. This demonstrates that noninvasive imaging with an anti-iC3b/C3d probe can be used to monitor inflammation in the kidneys.

Clinical Significance of C3d Assay in Kidney Transplant Recipients With Donor-Specific Anti-Human Leukocyte Antigen Antibodies.

BACKGROUND: Antibody-mediated rejection (AMR) is a major cause of allograft loss in kidney transplant. Although donor-specific anti-human leukocyte antigen antibody (DSA) is a key cause of AMR, not all patients with DSA are diagnosed as having AMR and show poor allograft outcomes. This study aimed to evaluate clinical significance of C3d-binding activity in patients with DSA identified by single-antigen bead (SAB) assay. METHODS: A total of 168 recipients screened for DSA from 2015 to 2018 were enrolled. Among them, 52 patients had DSA confirmed by SAB assay. Sera were tested using the C3d assay on Luminex platform. AMR was defined by kidney allograft biopsy results using Banff 2015 criteria. RESULTS: Of 52 patients, C3d-binding DSAs were detected in 22 patients (42.3%). Indication allograft biopsy was performed in 35 patients, with 31 (88.6%) diagnosed as having AMR. Patients with C3d-binding DSA had more class II SAB-DSA (73.3% vs 100%, P = .015) and showed significantly higher mean (SD) fluorescence intensity of class II SAB-DSA than the C3d-binding DSA(-) group (9606.7 [6096.6] vs 1921.0 [1483.8], P < .001). There was a positive correlation in the highest mean fluorescence intensity between class II SAB-DSA and class II C3d-binding DSA (r = 0.70, P < .001). Patients with C3d-binding DSA showed worse death-censored graft survival than those with non-C3d-binding DSA (P = .023). CONCLUSIONS: This study showed that presence of C3d-binding DSA was significantly associated with allograft loss in SAB-DSA-positive patients. Further trials are warranted.

Intra-Liver Allograft C3d-Binding Donor-Specific Anti-HLA Antibodies Predict Rejection After Liver Transplantation.

BACKGROUND: There is no doubt that antibody-mediated rejection (AMR) due to donor-specific anti-HLA antibodies (DSA) brings a poor outcome for liver transplant recipients. However, the relationship between intragraft DSA (g-DSA), complement-binding abilities, and AMR remains unknown. MATERIALS AND METHODS: We enrolled a total of 20 liver transplant recipients who underwent protocol or episode graft biopsies in the mid to long term after liver transplant (median 48.5, range 6-198 months), and their status of g-DSA and complement 3d (C3d)-binding abilities was assessed with the graft immunocomplex capture fluorescence analysis (ICFA) technique. RESULTS: The prevalence of g-DSA was 15.0 % in liver transplant recipients (3/20), and serum DSA (s-DSA) also existed in 15.0% of recipients. The number of g-DSA+/s-DSA+, g-DSA+/s-DSA-, g-DSA-/s-DSA+, and g-DSA-/s-DSA- cases are 1, 2, 2, and 15, respectively. The g-DSA+ group demonstrated a significant high rejection activity index: 3.67 ± 1.53, compared with the g-DSA- group: 1.24 ± 1.15 (P = .0045). Moreover, C3d-binding reaction was notably higher in the g-DSA+ group (C3d index: 1.87 ± 0.38 vs 0.76 ± 0.35) (P < .0001). Overall, the g-DSA+ group was more associated with liver allograft rejection-not only AMR, but also T cell-mediated rejection (P = .031). CONCLUSIONS: These results suggest that the existence of g-DSA and intragraft C3d-binding reaction had a negative impact on the liver allografts, but in contrast s-DSA did not have any significant impact.

Complement C3d is not associated with axial spondyloarthritis and magnetic resonance imaging changes at the sacroiliac joint.

OBJECTIVE: To investigate the associations between complement C3d and inflammatory and structural changes by magnetic resonance imaging (MRI) at the sacroiliac joints (SIJ) suggestive of axial spondyloarthritis, according to the Assessment of SpondyloArthritis international Society (ASAS) criteria, in patients with low back pain. METHOD: This was a cross-sectional study of patients referred to the Spine Centre of Southern Denmark owing to unspecified low back pain (Spines of Southern Denmark cohort). The patients were divided into three groups: group 1: patients fulfilling the ASAS criteria for axial spondyloarthritis (axSpA, n = 96); group 2: patients with either a positive MRI of the SIJ and no spondyloarthritis features, or a negative MRI of the SIJ but positive human leucocyte antigen-B27 and one spondyloarthritis feature (non-axSpA, n = 38); group 3: patients with unspecified low back pain for > 3 months (control group, n = 82). Complement C3d was measured with double-decker rocket immunoelectrophoresis and evaluated in relation to the group division and baseline findings by SIJ MRI. RESULTS: In total, 184 C3d analyses were performed. The mean ± sd level of C3d was 33.8 ± 8.1 AU/mL. There were no differences in C3d levels between the three patient groups, mean values being: axSpA = 34.3 ± 7.9 AU/mL, non-axSpA = 33.5 ± 6.9 AU/mL, and controls = 33.4 ± 9.2 AU/mL. The level of C3d was not related to MRI findings. CONCLUSIONS: In these patients, complement C3d was not associated with active or structural SIJ changes on MRI suggestive of axial spondyloarthritis.

Insights Into the Structure-Function Relationships of Dimeric C3d Fragments.

Cleavage of C3 to C3a and C3b plays a central role in the generation of complement-mediated defences. Although the thioester-mediated surface deposition of C3b has been well-studied, fluid phase dimers of C3 fragments remain largely unexplored. Here we show C3 cleavage results in the spontaneous formation of C3b dimers and present the first X-ray crystal structure of a disulphide-linked human C3d dimer. Binding studies reveal these dimers are capable of crosslinking complement receptor 2 and preliminary cell-based analyses suggest they could modulate B cell activation to influence tolerogenic pathways. Altogether, insights into the physiologically-relevant functions of C3d(g) dimers gained from our findings will pave the way to enhancing our understanding surrounding the importance of complement in the fluid phase and could inform the design of novel therapies for immune system disorders in the future.

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.

Systemic complement activation levels in Stargardt disease.

PURPOSE: Preclinical research provides evidence for the complement system as a potential common pathway in Stargardt disease (STGD1) and age-related macular degeneration (AMD) leading to retinal pigment epithelium (RPE) loss. However, systemic complement activation has not yet been assessed in STGD1 patients. We conducted a cross-sectional case-control study to assess systemic complement activation in STGD1 patients and its association with disease severity. METHODS: Systemic concentrations of complement component C3 and its degradation product C3d were compared between 80 STGD1 patients and 80 controls that were frequency matched for age and sex. The C3d/C3 ratio was used as parameter of systemic complement activation. Within the STGD1 cohort, we additionally examined the association between the C3d/C3 ratio, demographic and behavioural factors (age, sex, smoking and BMI), and measures of disease severity (age at onset, visual acuity, and area of atrophy). RESULTS: The C3d/C3 ratio did not significantly differ between patients (mean C3d/C3 ratio 3.5±1.4) and controls (mean C3d/C3 ratio 3.6±1.0), mean difference -0.156 (p = 0.804, independent samples t-test). The overall effect size was 8% (95% confidence interval, 3-15%). Elevated C3d/C3 ratios (>8.1) were found in three patients who all had a concomitant inflammatory condition at the time of blood draw. Within the patient cohort, C3 levels were associated with sex (mean difference -134, p = 0.001, independent samples t-test) and BMI (correlation coefficient 0.463, p<0.001, Spearman's Correlation). CONCLUSIONS: Systemic complement levels were not elevated in STGD1 patients compared to age and sex matched controls and was not associated with STGD1 severity. Considering the continued absent proof of a systemic contribution of the complement system to RPE loss in STGD1 patients, we hypothesize that complement activation in STGD1 is more likely a local process. In light of upcoming complement-targeted therapies, further studies are needed that measure complement levels in the eye of STGD1 patients.

Intensity of de novo DSA detected by Immucor Lifecodes assay and C3d fixing antibodies are not predictive of subclinical ABMR after Kidney Transplantation.

De novo donor-specific antibodies (dnDSA) are associated with antibody-mediated rejection (ABMR) and allograft loss. We tested Immucor* (IM) Luminex Single-antigen beads (LSAB) assay and C3d-fixing antibodies in the setting of dnDSA and subclinical (s) ABMR. This retrospective multicentric study included 123 patients biopsied because of the presence of subclinical de novo DSA detected by One Lamda* Labscreen (MFI > 1000). In 112 patients, sera of the day of the biopsy were available and tested in a central lab with IM Lifecodes LSAB and C3d fixing antibodies assays. In 16 patients (14.3%), no DSA was detected using Immucor test. In 96 patients, at least one DSA was determined with IM. Systematic biopsies showed active sABMR in 30 patients (31.2%), chronic active sABMR in 17 patients (17.7%) and no lesions of sABMR in 49 KT recipients (51%). Intensitity criteria (BCM, BCR and AD-BCR) of DSA were not statistically different between these 3 histological groups. The proportion of patients with C3d-fixing DSA was not statistically different between the 3 groups and did not offer any prognostic value regarding graft survival. Performing biopsy for dnDSA could not be guided by the intensity criteria of IM LSAB assay. C3d-fixing DSA do not offer added value.

Modular complement assemblies for mitigating inflammatory conditions.

Complement protein C3dg, a key linkage between innate and adaptive immunity, is capable of stimulating both humoral and cell-mediated immune responses, leading to considerable interest in its use as a molecular adjuvant. However, the potential of C3dg as an adjuvant is limited without ways of controllably assembling multiple copies of it into vaccine platforms. Here, we report a strategy to assemble C3dg into supramolecular nanofibers with excellent compositional control, using ß-tail fusion tags. These assemblies were investigated as therapeutic active immunotherapies, which may offer advantages over existing biologics, particularly toward chronic inflammatory diseases. Supramolecular assemblies based on the Q11 peptide system containing ß-tail-tagged C3dg, B cell epitopes from TNF, and the universal T cell epitope PADRE raised strong antibody responses against both TNF and C3dg, and prophylactic immunization with these materials significantly improved protection in a lethal TNF-mediated inflammation model. Additionally, in a murine model of psoriasis induced by imiquimod, the C3dg-adjuvanted nanofiber vaccine performed as well as anti-TNF monoclonal antibodies. Nanofibers containing only ß-tail-C3dg and lacking the TNF B cell epitope also showed improvements in both models, suggesting that supramolecular C3dg, by itself, played an important therapeutic role. We observed that immunization with ß-tail-C3dg caused the expansion of an autoreactive C3dg-specific T cell population, which may act to dampen the immune response, preventing excessive inflammation. These findings indicate that molecular assemblies displaying C3dg warrant further development as active immunotherapies.

Cloning and structural analysis of complement component 3d in wild birds provides insight into its functional evolution.

Complement component 3 d (C3d) is the final cleavage product of the complement component C3 and serves as a crucial role in link innate and adaptive immunity, and increase B-cell sensitivity to an antigen by 1000-10000 fold. The crystal structure of human C3d revealed there are two distinct surfaces, a convex surface containing the thioester-constituting residues that mediate covalent binding to the target antigen, and a concave surface with an acidic pocket responsible for interaction with CR2. In this study, we cloned and sequenced cDNA fragment encoding C3d region from 15 wild bird species. Then, the C3d sequences from wild birds, chicken and mammals were aligned to construct phylogenetic trees. Phylogenetic tree displayed two main branches, indicating mammals and birds, but the bird C3d branch was divided into two main parts, with five wild birds (Ardeola bacchus, Zoothera, Bubo, Crossoptilon mantchuricum and Caprimulgus europaeus) clustering much closer to mammals. In addition, the C3d proteins of Ardeola bacchus, Bubo, Crossoptilon mantchuricum and Caprimulgus europaeus contained a Glu163 residue at the position at which Lys163 was found in other birds. However, Glu163 have the same charge polarity as Asp163, which is the key amino acid residue comprising the acidic pocket combined with CR2 found at this position in mammals, and Zoothera also possessed Asp163 at this position. Structure modeling analyses also verified that the C3ds of these five wild bird species exhibited the amino acid sequence and structure comprising the typical acidic pocket found in mammals that is required for combination with B cell surface receptors, which contribute electrostatic forces to interact with CR2. Our investigations indicate that some bird C3ds may already have the ability to bind with CR2 by electrostatic force, like mammals. As Ardeola bacchus, Zoothera, Bubo, Crossoptilon mantchuricum and Caprimulgus europaeus have more typical C3d concave acid pockets and thus a stronger ability to bind CR2, we speculate that these five wild birds may have a solider immunity against pathogens. Our phylogenetic and structural analyses of bird C3ds provide insights on the evolutionary divergence in the function of immune factors of avian and mammalian.

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.

Missing Self-Induced Activation of NK Cells Combines with Non-Complement-Fixing Donor-Specific Antibodies to Accelerate Kidney Transplant Loss in Chronic Antibody-Mediated Rejection.

BACKGROUND: Binding of donor-specific antibodies (DSAs) to kidney allograft endothelial cells that does not activate the classic complement cascade can trigger the recruitment of innate immune effectors, including NK cells. Activated NK cells contribute to microvascular inflammation leading to chronic antibody-mediated rejection (AMR). Recipient NK cells can also trigger antibody-independent microvascular inflammation by sensing the absence of self HLA class I molecules ("missing self") on allograft endothelial cells. This translational study investigated whether the condition of missing self amplifies DSA-dependent NK cell activation to worsen chronic AMR. METHODS AND RESULTS: Among 1682 kidney transplant recipients who underwent an allograft biopsy at Lyon University Hospital between 2004 and 2017, 135 fulfilled the diagnostic criteria for AMR and were enrolled in the study. Patients with complement-fixing DSAs identified by a positive C3d binding assay (n=73, 54%) had a higher risk of transplant failure (P=0.002). Among the remaining patients with complement-independent chronic AMR (n=62, 46%), those in whom missing self was identified through donor and recipient genotyping exhibited worse allograft survival (P=0.02). In multivariable analysis, only proteinuria (HR: 7.24; P=0.01) and the presence of missing self (HR: 3.57; P=0.04) were independent predictors for transplant failure following diagnosis of chronic AMR. Cocultures of human NK cells and endothelial cells confirmed that addition of missing self to DSA-induced NK cell activation increased endothelial damage. CONCLUSIONS: The assessment of missing self at the time of diagnosis of chronic AMR identifies patients at higher risk for kidney transplant failure.

Enfermedad por aglutininas frías: proceso diagnóstico, tratamiento y seguimiento de un paciente / Cold agglutinin disease: diagnosis, treatment and follow-up of a patient

La enfermedad por crioaglutininas es una anemia hemolítica autoinmune que se caracteriza, en la gran mayoría de los casos, por la hemólisis mediada por autoanticuerpos de tipo IgM y complemento C3d, contra los antígenos de la membrana del eritrocito, que conduce a hemólisis extravascular con propensión a la trombosis, y que afecta principalmente al sexo femenino y personas mayores. Su diagnóstico se realiza con la prueba de Coombs directo y fraccionado, y la titulación de aglutininas frías >1:64 a 4 °C. Se describe el caso clínico de una mujer de 89 años con un síndrome constitucional y una anemia de 3 años de evolución, en quien se determinó el diagnóstico de enfermedad por aglutininas frías. Asimismo, se describe el abordaje diagnóstico, el tratamiento instaurado, y se hace una breve revisión de la literatura publicada

Cold agglutinin disease (CAD) is an autoimmune hemolytic anemia characterized in the vast majority of cases by hemolysis mediated by IgM autoantibodies and complement C3d against erythrocyte membrane antigens, leading to extravascular hemolysis with propensity to thrombosis, affecting mainly females and older individuals. It is diagnosed by direct and fractionated Coombs test and a cold agglutinin titer >1:64 at 4 °C. We describe the case of an 89-year-old woman with a constitutional syndrome and a 3-year history of anemia, who was diagnosed with cold agglutinin disease. Also, we include the diagnostic and treatment approach, and a brief review of the literature

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.

Notch signaling induces a transcriptionally permissive state at the Complement C3d Receptor 2 (CR2) promoter in a pre-B cell model.

During mammalian lymphoid development, Notch signaling is necessary at multiple stages of T lymphopoiesis, including lineage commitment, and later stages of T cell effector differentiation. In contrast, outside of a defined role in the development of splenic marginal zone B cells, there is conflicting evidence regarding whether Notch signaling plays functional roles in other B cell sub-populations. Complement receptor 2 (CR2) modulates BCR-signaling and is tightly regulated throughout differentiation. During B lymphopoiesis, CR2 is detected on immature and mature B cells with high surface expression on marginal zone B cells. Here, we have explored the possibility that Notch regulates human CR2 transcriptional activity using in vitro models including a co-culture system, co-transfection gene reporters and chromatin accessibility assays. We provide evidence that Notch signaling regulates CR2 promoter activity in a mature B cell line, as well as the induction of endogenous CR2 mRNA in a non-expressing pre-B cell line. The dynamics of endogenous gene activation suggests additional unidentified factors are required to mediate surface CR2 expression on immature and mature B lineage cells.