Erythrocyte Complement Receptor Research Articles

Elucidation of the low-expressing erythroid CR1 phenotype by bioinformatic mining of the GATA1-driven blood-group regulome

Genetic determinants underlying most human blood groups are now clarified but variation in expression levels remains largely unexplored. By developing a bioinformatics pipeline analyzing GATA1/Chromatin immunoprecipitation followed by sequencing (ChIP-seq) datasets, we identify 193 potential regulatory sites in 33 blood-group genes. As proof-of-concept, we aimed to delineate the low-expressing complement receptor 1 (CR1) Helgeson phenotype on erythrocytes, which is correlated with several diseases and protects against severe malaria. We demonstrate that two candidate CR1 enhancer motifs in intron 4 bind GATA1 and drive transcription. Both are functionally abolished by naturally-occurring SNVs. Erythrocyte CR1-mRNA and CR1 levels correlate dose-dependently with genotype of one SNV (rs11117991) in two healthy donor cohorts. Haplotype analysis of rs11117991 with previously proposed markers for Helgeson shows high linkage disequilibrium in Europeans but explains the poor prediction reported for Africans. These data resolve the longstanding debate on the genetic basis of inherited low CR1 and form a systematic starting point to investigate the blood group regulome.

Erythrocyte complement receptor 1 (ECR1) and erythrocyte-bound C4d (EC4d) in the prediction of poor pregnancy outcomes in systemic lupus erythematosus (SLE)

BackgroundComplement activation has been associated with adverse pregnancy outcomes (APO) in SLE. Pregnant women with SLE were studied to evaluate whether complement dysregulation within the first two pregnancy trimesters predicts...

Erythrocyte Complement Receptor 1 Gene Polymorphisms and Neonatal Respiratory Distress Syndrome.

To evaluate the role of erythrocyte complement receptor 1 ( ECR1 ) gene in the predisposition to respiratory distress syndrome (RDS), we studied 50 infants with RDS and 50 controls. Real-time polymerase chain reaction allelic discrimination analysis of A3650G (rs2274567) and genotyping of the alleles (HindIII) were performed. Allele L of HindIII restricted single nucleotide polymorphism (SNP) associated with the severity of RDS. Duration of oxygen and ventilation in genotypes AA and AG of A3650G SNP was longer than genotype GG (17.6 ± 19.4 and 8.6 ± 4.5 days, p = 0.01) and (8.9 ± 11.9 and 3.9 ± 3.53 days, p = 0.03), respectively. A3650G and HINDIII digested gene polymorphisms of ECR1 may be of little importance for RDS.

Clearance of amyloid-beta with bispecific antibody constructs bound to erythrocytes.

We propose use of bispecific monoclonal antibody (mAb) complexes bound to erythrocytes to redress the lack of efficacy of anti‐amyloid beta mAbs in Alzheimer's disease treatment. Our paradigm leverages erythrocyte complement receptor 1 to promote rapid and quantitative removal of amyloid beta from the circulation, and its subsequent removal from the brain as well.

Key role of the number of complement receptor 1 on erythrocytes for binding of Escherichia coli to erythrocytes and for leukocyte phagocytosis and oxidative burst in human whole blood

AimTo study the role of complement receptor 1 (CR1) for binding of Escherichia coli (E. coli) to erythrocytes, for leukocyte phagocytosis, oxidative burst and complement activation in human whole blood from a CR1 deficient (CR1D) patient and healthy controls with low, medium and high CR1 numbers. MethodsAlexa-labelled bacteria were used to quantify erythrocyte-bound bacteria, free bacteria in plasma and phagocytosis using flow cytometry. Complement activation in plasma was measured by enzyme-linked immunosorbent assay. The CR1 numbers as well as C3bc and C4bc deposition on erythrocytes were measured by flow cytometry. Cytokines were measured using multiplex technology, and bacterial growth was measured by colony forming units. CR1 was blocked using the anti-CR1 blocking mAb 3D9. ResultsApproximately 85% of E. coli bound to erythrocytes after 15 min incubation in donor blood with high and medium CR1 numbers, 50% in the person with low CR1 numbers and virtually no detectable binding in the CR1D (r2 = 0.87, P < 0.0007). The number of free bacteria in plasma was inversely related to erythrocyte CR1 numbers (r2 = 0.98, P < 0.0001). E. coli-induced phagocytosis and oxidative burst were significantly enhanced by the anti-CR1 mAb 3D9 and in the CR1D and the donor with low CR1 numbers. E. coli-induced complement activation in plasma, C3bc and C4bc deposition on erythrocytes, and bacterial growth were similar in all four cases. ConclusionsCR1D and low CR1 numbers prevented E. coli binding to erythrocytes, increased free bacteria in plasma, phagocytosis and oxidative burst, but did not affect plasma or surface complement activation and bacterial growth.

Peripheral complement interactions with amyloid β peptide in Alzheimer's disease: Polymorphisms, structure, and function of complement receptor 1

IntroductionGenome-wide association studies consistently show that single nucleotide polymorphisms (SNPs) in the complement receptor 1 (CR1) gene modestly but significantly alter Alzheimer's disease (AD) risk. Follow-up research has assumed that CR1 is expressed in the human brain despite a paucity of evidence for its function there. Alternatively, erythrocytes contain >80% of the body's CR1, where, in primates, it is known to bind circulating pathogens. MethodsMultidisciplinary methods were employed. ResultsConventional Western blots and quantitative polymerase chain reaction failed to detect CR1 in the human brain. Brain immunohistochemistry revealed only vascular CR1. By contrast, erythrocyte CR1 immunoreactivity was readily observed and was significantly deficient in AD, as was CR1-mediated erythrocyte capture of circulating amyloid β peptide. CR1 SNPs associated with decreased erythrocyte CR1 increased AD risk, whereas a CR1 SNP associated with increased erythrocyte CR1 decreased AD risk. DiscussionSNP effects on erythrocyte CR1 likely underlie the association of CR1 polymorphisms with AD risk.

No Evidence that Knops Blood Group Polymorphisms Affect Complement Receptor 1 Clustering on Erythrocytes

Clustering of Complement Receptor 1 (CR1) in the erythrocyte membrane is important for immune-complex transfer and clearance. CR1 contains the Knops blood group antigens, including the antithetical pairs Swain-Langley 1 and 2 (Sl1 and Sl2) and McCoy a and b (McCa and McCb), whose functional effects are unknown. We tested the hypothesis that the Sl and McC polymorphisms might influence CR1 clustering on erythrocyte membranes. Blood samples from 125 healthy Kenyan children were analysed by immunofluorescence and confocal microscopy to determine CR1 cluster number and volume. In agreement with previous reports, CR1 cluster number and volume were positively associated with CR1 copy number (mean number of CR1 molecules per erythrocyte). Individuals with the McCb/McCb genotype had more clusters per cell than McCa/McCa individuals. However, this association was lost when the strong effect of CR1 copy number was included in the model. No association was observed between Sl genotype, sickle cell genotype, α+thalassaemia genotype, gender or age and CR1 cluster number or volume. Therefore, after correction for CR1 copy number, the Sl and McCoy polymorphisms did not influence erythrocyte CR1 clustering, and the effects of the Knops polymorphisms on CR1 function remains unknown.

Peripheral complement interactions with amyloid β peptide: Erythrocyte clearance mechanisms

IntroductionAlthough amyloid β peptide (Aβ) is cleared from the brain to cerebrospinal fluid and the peripheral circulation, mechanisms for its removal from blood remain unresolved. Primates have uniquely evolved a highly effective peripheral clearance mechanism for pathogens, immune adherence, in which erythrocyte complement receptor 1 (CR1) plays a major role. MethodsMultidisciplinary methods were used to demonstrate immune adherence capture of Aβ by erythrocytes and its deficiency in Alzheimer's disease (AD). ResultsAβ was shown to be subject to immune adherence at every step in the pathway. Aβ dose-dependently activated serum complement. Complement-opsonized Aβ was captured by erythrocytes via CR1. Erythrocytes, Aβ, and hepatic Kupffer cells were colocalized in the human liver. Significant deficits in erythrocyte Aβ levels were found in AD and mild cognitive impairment patients. DiscussionCR1 polymorphisms elevate AD risk, and >80% of human CR1 is vested in erythrocytes to subserve immune adherence. The present results suggest that this pathway is pathophysiologically relevant in AD.

Elevated lead levels and changes in blood morphology and erythrocyte CR1 in preschool children from an e-waste area

Improper dismantling and combustion of electronic waste (e-waste) may release persistent organic pollutants and heavy metals that possess potential risk for human health. Lead (Pb) is carried through the circulatory system by erythrocytes and is known to alter the functions of hematopoietic and immune systems. The aim of the study was to investigate the effect of Pb exposure on blood morphology and erythrocyte complement receptor 1 (CR1) levels as related to immunologic function in preschool children. We recruited 484 preschool children, 2- to 6-years of age, among whom 332 children were from Guiyu, a typical and primitive e-waste processing area, and 152 children from Haojiang (reference area). Results showed that the blood Pb level (BPb) and erythrocyte Pb level (EPb) of exposed children were significantly higher, but, the mean corpuscular hemoglobin concentration (MCHC) and erythrocyte CR1 levels were significantly lower than reference children. Elevated EPb and BPb was related to disadvantageous changes in hematocrit (HCT), mean corpuscular volume (MCV), hemoglobin (HGB), mean corpuscular hemoglobin (MCH), and MCHC, respectively, in children from the e-waste recycling area. Furthermore, in the high Pb-exposed group, the Pb toxicity of erythrocytes was more significant compared to the low Pb-exposed group in e-waste-exposed children. Combine with the BPb and EPb would be better to evaluating the Pb toxicity of erythrocytes. Compared to low Pb exposure, high BPb and EPb were associated with lower erythrocyte CR1 expression in all children. Our data suggests that elevated Pb levels result in adverse changes in blood morphology, hemoglobin synthesis and CR1 expression, which might be a non-negligible threat to erythrocyte immunity development in local preschool children. It is therefore imperative for any intervention to control the Pb exposure of children and actively educate adults to raise their environmental awareness of potential e-waste pollution during the recycling process.

Effects of Ulinastatin on In Vitro Storage Lesions of Human Red Blood Cells.

The study aimed to investigate the influence of in vitro storage on erythrocyte complement receptor one (E-CR1), cell shrinkage and eryptosis of human red blood cells (RBCs), and to assess the possible effects of ulinastatin (UTI) on them. After collection, RBCs were treated with saline (control group) and different concentrations of UTI (5,000 U/mL, 10,000 U/mL, and 50,000 U/mL in Group C1, Group C2, and Group C3, respectively). E-CR1, cell size, and phosphatidylserine (PS) exposure and intracellular Ca2+ concentration were analyzed by flow cytometer every 7 days up to Day 35. E-CR1 level and cell size of all groups decreased during storage. In the control group, E-CR1 began to decrease on Day 28 and cells shrank on Day 21. The E-CR1 level of Group C2 was significantly higher than that of the control group beginning on Day 21. The cells of Group C1 and Group C2 began to shrink remarkably on Day 21, and those of Group C3 on Day 35. PS-exposure levels of 4 groups started to increase on Day 7 (p < 0.05), while from Day 14 to 35 those of Group C3 were significantly lower than the control group (p < 0.05). The intracellular Ca2+ levels of the control group started to increase significantly on Day 7, one week earlier than the experimental groups. From Day 21 to 35, the intracellular Ca2+ levels of Group C2 and C3 were significantly lower than those of the control group (p < 0.05). RBCs underwent E-CR1 loss, cell shrinkage, and eryptosis during in vitro storage, which could be attenuated by UTI.

Association of the single-nucleotide polymorphism and haplotype of the complement receptor 1 gene with malaria.

PurposeAlthough the polymorphisms of erythrocyte complement receptor type 1 (CR1) in patients with malaria have been extensively studied, a question of whether the polymorphisms of CR1 are associated with severe malaria remains controversial. Furthermore, no study has examined the association of CR1 polymorphisms with malaria in Chinese population. Therefore, we investigated the relationship of CR1 gene polymorphism and malaria in Chinese population.Materials and MethodsWe analyzed polymorphisms of CR1 gene rs2274567 G/A, rs4844600 G/A, and rs2296160 C/T in 509 patients with malaria and 503 controls, using the Taqman genotyping assay and PCR-direct sequencing.ResultsThere were no significant differences in the genotype, allele and haplotype frequencies of CR1 gene rs2274567 G/A, rs4844600 G/A, and rs2296160 C/T polymorphisms between patients with malaria and controls. Furthermore, there was no association of polymorphisms in the CR1 gene with the severity of malaria in Chinese population.ConclusionThese findings suggest that CR1 gene rs2274567 G/A, rs4844600 G/A, and rs2296160 C/T polymorphisms may not be involved in susceptibility to malaria in Chinese population.

Mechanisms of enhanced neutralization of botulinum neurotoxin by monoclonal antibodies conjugated to antibodies specific for the erythrocyte complement receptor

Immune complexes formed between monoclonal antibodies (mAbs) and toxins can neutralize toxicity in vivo by multiple mechanisms. Toxin sequestration and clearance by mAbs may be improved by enhancing their ability to bind to red blood cells (RBCs) through immune adherence. This can be achieved by converting the mAbs to heteropolymers (HPs), which are antigen-specific mAbs cross-linked to mAbs targeting the complement receptor (CR1), a protein that is expressed on the surface of RBCs in primates and mediates delivery of complement C3b-containing immune complexes to tissue macrophages. Conversion of mAbs to HPs has been shown to enhance clearance of multivalent antigens from the blood circulation, but the interaction of HPs with monovalent toxins has not been examined. Using botulinum neurotoxin (BoNT) as a model system, we studied the effect of conversion of a pair of BoNT-specific mAbs into HPs on toxin neutralization and handling in vivo. Two HPs given in combination had 166-fold greater potency than un-modified mAbs, neutralizing 5000 LD50 BoNT, when tested in transgenic mice expressing human CR1 on RBC membranes. Improvement required adherence of BoNT to the RBC in vivo and 2 HPs, rather than an HP+mAb pair. The HP pair bound BoNT to RBCs in the circulation for 2h, in comparison to BoNT-neutralizing anti-serum, which induced no detectable RBC binding. HP pairs exhibited enhanced uptake by peritoneal macrophages in vitro, compared to pairs of mAbs or mAb+HP pairs. In a post-exposure therapeutic model, HPs gave complete protection from a lethal BoNT dose up to 3h after toxin exposure. In a pre-exposure prophylaxis model, mice given HP up to 5 days prior to BoNT administration were fully protected from a lethal BoNT dose. These studies elucidate general mechanisms for the neutralization of toxins by HP pairs and demonstrate the potential utility of HPs as BoNT therapeutics.

Beta-Thalassemia Minor Is Associated with IgA Nephropathy

Jung Hyun Kang, M.D., Bo Rha Park, M.D., Kyung Soo Kim, M.D., Do Yeun Kim, M.D., Hee Jin Huh, M.D., Seok Lae Chae, M.D., and Sung Joon Shin, M.D.. Ann Lab Med 2013;33:153-5. https://doi.org/10.3343/alm.2013.33.2.153

Expression of complement receptor type 1 on erythrocytes and its correlation with immunoglobulin E,complement C3 and C4 expressions in patients with chronic urticaria

Objective To investigate the role of erythrocyte complement receptor type 1 (CR1) in the pathogenesis of chronic urticaria.Methods Venous blood samples were collected from 59 patients with chronic urticaria (including 14 cases of dermatographism and 45 chronic idiopathic urticaria) and 29 healthy human controls.Flow cytometry was carried out to quantify the expression level of CR1,and double-antibody sandwich enzyme-linked immunosorbent assay to determine the serum level of immunoglobulin E (IgE),complement C3,C4 and 50％ complement hemolytic activity (CH50).Differences in these parameters were analyzed by one-way ANOVA and independent samples t-test,and correlation between these paramenters by Pearson correlation analysis.Results The expression level (expressed as mean fluorescence intensity per 10 000 erythrocytes) of CR1 was significantly higher in patients with dermatographism and chronic idiopathic urticaria than in the healthy controls (35.06 ± 2.06 and 29.17 ± 1.53 vs.20.46 ± 2.57,t =4.20 and 3.33,both P ＜ 0.05),while no statistical difference was observed between the patients with dermatographism and chronic idiopathic urticaria (P ＞ 0.05).Increased total serum IgE levels were observed in patients with dermatographism and chronic idiopathic urticaria compared with the healthy controls ((769.89 ± 123.0) μg/L and (340.09 ± 29.74) μg/L vs.(107.63 ± 88.79) μg/L,t =5.58,5.85,both P ＜ 0.05),and in patients with dermatographism compared with those with chronic idiopathic urticaria (t =3.49,P ＜ 0.05).For patients with chronic urticaria,there was a statistical difference in the expression level of CR1 between individuals (n=22) with total serum IgE levels ranging from 0 to 240 μg/L and those (n =17) higher than 500 μg/L (24.45 ± 10.83 vs.33.09 ± 11.86,t =3.33,P＜ 0.05).The total serum IgE levels were positively correlated with the level of CR1 (r =0.27,P ＜ 0.05),but uncorrelated with that of complement C3 (r =0.16,P ＞ 0.05) or C4 (r =-0.08,P＞ 0.05).The level of complement C3 was positively correlated with that of C4 (r =0.54,P ＜ 0.01).One-way ANOVA revealed no significant difference in the serum levels of complement C3,C4,or CH50 between the patients with dermatographism,patients with chronic idiopathic urticaria and healthy controls (all P ＞ 0.05).Conclusion CR1 is abnormally expressed in patients with chronic urticaria. Key words: Urticaria; Receptors, complement; Complement C3; Complement C4; Immunoglobulin E

Dual role of erythrocyte complement receptor type 1 in immune complex-mediated macrophage stimulation: implications for the pathogenesis ofPlasmodium falciparummalaria

Given the ability of erythrocytes to bind immune complexes (ICs), we postulated that they can serve a dual role during inflammatory or infectious processes. Erythrocytes could restrict stimulation of macrophages by free ICs by binding C3b-opsonized ICs via their complement receptor 1 (CR1). Conversely, IC-loaded erythrocytes could stimulate macrophages to produce proinflammatory cytokines such as tumour necrosis factor (TNF)-α. To test our hypothesis we selected 72 individuals with low, medium or high red cell CR1 expression and determined their IC binding capacity. We tested the in vitro ability of red cells to inhibit IC-mediated stimulation of TNF-α production by macrophages or to stimulate TNF-α production when loaded with ICs. Plain erythrocytes inhibited IC-induced TNF-α production by macrophages and low CR1 expressors showed the lowest inhibitory capacity. IC-loaded erythrocytes stimulated macrophages to release TNF-α, but the effect was not proportional to the CR1 level. These data support our hypothesis that erythrocytes can serve a dual role in regulation of cytokine responses in a setting of IC formation. Our findings suggest that individuals with low CR1 expression are ill-equipped to clear ICs and prevent IC-mediated stimulation of macrophages. In addition, IC-loaded red cells in areas of sluggish circulation such as in the spleen or in brain capillaries blocked by sequestered malaria-infected red cells may induce inflammation by stimulating monocytes and macrophages, the latter leading to the development of cerebral malaria.

Neisseria meningitidis and Escherichia coli are protected from leukocyte phagocytosis by binding to erythrocyte complement receptor 1 in human blood

The initial interaction of Gram-negative bacteria with erythrocytes and its implications on leukocyte phagocytosis and oxidative burst in human whole blood were examined. Alexa-labeled Escherichia coli, wild-type H44/76 N. meningitidis and the H44/76lpxA lipopolysaccharide (LPS)-deficient mutant were incubated with whole blood using lepirudin as anticoagulant which has no adverse effects on complement. Bacteria free in plasma, bound to erythrocytes or phagocytized by granulocytes and monocytes were quantified using flow cytometry. The effects of the C3 inhibitor compstatin, a C5a receptor antagonist (C5aRa) and a complement receptor 1 (CR1)-blocking antibody (3D9) were examined. Most bacteria (80%) immediately bound to erythrocytes. The binding gradually declined over time, with a parallel increase in phagocytosis. Complement inhibition with compstatin reduced erythrocyte binding and bacterial C3 opsonization. In contrast, the C5aRa efficiently reduced phagocytosis, but did not affect the binding of bacteria to erythrocytes. The anti-CR1 blocking mAb dose-dependently reduced bacterial binding to erythrocytes to nil, with subsequent increased phagocytosis and oxidative burst. LPS had no effect on these processes since similar results were obtained using an LPS-deficient N. meningitidis mutant. In vivo experiments in a pig model of sepsis showed limited binding of bacteria to erythrocytes, consistent with the facts that erythrocyte CR1 receptors are absent in non-primates and that the bacteria were mainly found in the lungs. In conclusion, complement-dependent binding of Gram-negative bacteria to erythrocyte CR1 decreases phagocytosis and oxidative burst by leukocytes in human whole blood.

Francisella tularensis: A Red-blooded Pathogen

Francisella tularensis: A Red-blooded Pathogen

Knops blood group polymorphism and susceptibility to Mycobacterium tuberculosis infection

Complement receptor 1 (CR1) protein carries the Knops blood group antigens and is the receptor for the major ligand involved in Mycobacterium tuberculosis (Mtb) adhesion to macrophages. Erythrocyte CR1 binds immune complexes (ICs) formed during Mtb invasion, facilitating their clearance by the host immune system. The occurrence of specific Knops blood group genotypes among African populations was investigated to evaluate their impact on resistance or susceptibility to Mtb infection. The distribution of the Knops blood group genotypes (McC and Sl) was compared between tuberculosis (TB) patients with confirmed diagnosis of Mtb in isolates and negative controls. Conditional logistic regression was used to access the association between genotypes distribution and susceptibility to Mtb infection. At the McC locus, individuals heterozygous (McC(a) /McC(b) ) were more resistant to Mtb infection (odds ratio [OR], 0.42; 95% confidence interval [CI], 0.22-0.81; p = 0.007). Although less significant, a similar effect was conferred by Sl1/Sl2 genotype (OR, 0.05; 95% CI, 0.28-0.9; p = 0.02). This protective effect was maintained among individuals presenting the McC(b) /Sl2 haplotype (OR, 0.25; 95% CI, 0.08-0.74; p = 0.008). Acquisition of McC(b) and Sl2 alleles among African population is correlated with resistance to Mtb infection, adding this bacterium to the list of mechanisms underlying the selection of the Knops blood group polymorphism among these populations.

Predictive Value of erythrocyte-bound C4d to erythrocyte-complement Receptor Type 1 Ratio in Lupus Disease Activity

Objective: Erythrocyte-bound C4d (E-C4d) and erythrocyte-complement receptor type 1 (E-CR1) are both novel biomarkers to diagnose systemic lupus erythematosus (SLE) and to monitor disease activity. This study aimed at determining the ratio of E-C4d to E-CR1 (E-C4d/E-CR1) using mouse monoclonal antibody CR1-2B11 and correlating the clinical association of this ratio with disease activity of SLE. Methods: This study included 6 SLE patients, and their blood samples were collected before and after immunosuppressive therapy. E-C4d and E-CR1 levels were measured using indirect immunofluorescence and flow cytometry on the same day as the blood drawing, and the E-C4d/E-CR1 ratios were calculated from the values obtained. Results: The mean of the E-C4d/E-CR1 ratio was significantly decreased in SLE patients after immunosuppressive therapy (12.93±1.9 vs. 3.52±0.9, p＜0.05). Three of the 6 SLE patients showed decreased ratios when their active disease stabilized after adequate treatment respectively (19.23 to 1.01, 5.47 to 1.25, and 13.16 to 2.40). Conclusion: The reciprocal change in E-C4d and E-CR1 levels is important in SLE patients. The E-C4d/E-CR1 ratio assessed with CR1-2B11 could be a good biomarker to predict disease activity and may be helpful in formulating a therapeutic strategy in SLE.

Reduced expression of erythrocyte complement receptor (C3bR) in MS.

The study was carried out in patients with MS (n-121) and in control group (n-519). On the basis of haemagglutination intensity and results of radioimmunoassay three phenotypes of complement receptor were classified: high HH, medium HL, and low LL. Considerable differences were observed in the distribution of these phenotypes between controls and MS in whom the low phenotype was more frequent. Family studies suggest that reduced expression of the complement receptor on the erythrocytes depends in MS on the disease process in the first place, and not on genetic factors.