C5a inhibitor protects against ischemia/reperfusion injury in rat small intestine.

Acute mesenteric ischemia (AMI) is caused by considerable intestinal injury, which is associated with intestinal ischemia followed by reperfusion. To elucidate the mechanisms of ischemia/reperfusion injuries, a C5a inhibitory peptide termed AcPepA was used to examine the role of C5a anaphylatoxin, induction of inflammatory cells, and cell proliferation of the intestinal epithelial cells in an experimental AMI model. In this rat model, the superior mesenteric artery was occluded and subsequently reperfused (Induce-I/R). Other groups were treated with AcPepA before ischemia or reperfusion. Induce-I/R induced injuries in the intestine and AcPepA significantly decreased the proportion of severely injured villi. Induce-I/R induced secondary receptor for C5a-positive polymorphonuclear leukocytes in the vessels and CD204-positive macrophages near the injured site; this was correlated with hypoxia-induced factor 1-alpha-positive cells. Induction of these inflammatory cells was attenuated by AcPepA. In addition, AcPepA increased proliferation of epithelial cells in the villi, possibly preventing further damage. Therefore, Induce-I/R activates C5a followed by the accumulation of polymorphonuclear leukocyte and hypoxia-induced factor 1-alpha-producing macrophages, leading to villus injury. AcPepA, a C5a inhibitory peptide, blocks the deleterious effects of C5a, indicating it has a therapeutic effect on the inflammatory consequences of experimental AMI.

Complement C5a inhibition improves late hemodynamic and inflammatory changes in a rat model of nonocclusive mesenteric ischemia.

BACKGROUND: Nonocclusive mesenteric ischemia (NOMI) can evolve in a variety of low-flow states. Although the mechanisms leading to NOMI-related intestinal necrosis are largely unknown, circumstantial evidence suggests that excessive vasoconstriction and complement activation both play important roles in this process. Because targeting of the circulatory malfunction of the splanchnic area could be of therapeutic relevance, we set out to investigate the long-term effects of treatment with a complement C5a antagonist in a rat model of partial aortic occlusion (PAO)-induced transient mesenteric hypoperfusion. METHODS: The mean arterial pressure of the splanchnic area was kept between 30 and 40 mm Hg by 60 minutes of PAO in anesthetized male Sprague-Dawley rats. C5a inhibitor acetyl-peptide-A (AcPepA; 4 mg kg(-1) intravenously) or vehicle administration was initiated at the 45th minute of PAO. After 24 hours, the animals were reanesthetized to record the macrohemodynamics and ileal microcirculation, and plasma and tissue samples were taken for determination of high-mobility group box protein-1 (HMGB-1), endothelin-1, tumor necrosis factor (TNF)-α levels, and small intestinal leukocyte infiltration. Epithelial structural changes were visualized by in vivo confocal laser scanning endomicroscopy. RESULTS: At 24 hours after PAO, mean arterial pressure, heart rate, and cardiac output were significantly greater, the intestinal intramural microcirculation was significantly impaired, and plasma HMGB-1, endothelin-1, TNF-α levels, the degree of epithelial damage and leukocyte infiltration was increased. The AcPepA treatment moderated the hemodynamic and microcirculatory changes, and decreased inflammatory activation and histologic signs of mucosal damage. CONCLUSION: C5a inhibition ameliorated the potentially harmful local mesenteric hypoperfusion and global long-term inflammatory consequences of PAO. This approach is of promise for use in NOMI-associated situations.

Complement C5A antagonist treatment improves the acute circulatory and inflammatory consequences of experimental cardiac tamponade.

OBJECTIVE: Cardiogenic shock often leads to splanchnic macro- and microcirculatory complications, and these events are linked to local and systemic inflammatory activation. Our aim was to investigate the consequences of complement C5a antagonist treatment on the early circulatory and inflammatory changes in a clinically relevant large animal model of cardiac tamponade. DESIGN AND SETTING: A randomized, controlled in vivo animal study in a university research laboratory. SUBJECTS: Anesthetized, ventilated, and thoracotomized Vietnamese mini pigs (24 ± 3 kg). INTERVENTIONS: Group 1 (n = 6) served as sham-operated control. In group 2 (n = 7), cardiac tamponade was induced for 60 minutes by the administration of intrapericardial fluid, while the mean arterial pressure was kept in the interval 40 to 45 mm Hg. Group 3 (n = 6) was treated with a complement C5a antagonist compound (the peptide acetyl-peptide-A, 4 mg/kg) after 45 minutes of tamponade. MEASUREMENTS AND MAIN RESULTS: The macrohemodynamics, including the superior mesenteric artery flow, was monitored; the average red blood cell velocity in the small intestinal mucosa was determined by an intravital orthogonal polarization imaging technique. The whole blood superoxide production, the plasma level of high-mobility group box protein-1 and big-endothelin and the small intestinal myeloperoxidase activity were measured. One hundred eighty minutes after the relief of tamponade, the mean arterial pressure was decreased, while the plasma levels of superoxide, high-mobility group box protein-1, and big-endothelin, and the intestinal myeloperoxidase activity were increased. The administration of acetyl-peptide-A normalized the mean arterial pressure and preserved the cardiac output, while the superior mesenteric artery flow and mucosal average red blood cell velocity were increased significantly, and the plasma superoxide, high-mobility group box protein-1, big-endothelin, and intestinal myeloperoxidase levels were reduced. CONCLUSIONS: These results provide evidence that blockade of the C5a effects significantly influences the acute splanchnic macro- and microhemodynamic complications and decreases the potentially harmful inflammatory consequences of experimental cardiogenic shock.

Anti-C5a complementary peptide ameliorates acute peritoneal injury induced by neutralization of Crry and CD59.

In peritoneal dialysis (PD) therapy, physical stresses such as exposure to peritoneal dialysate, catheter trauma, and peritonitis may induce peritoneal injury that can prevent continued long-term PD therapy. Therefore, protection of the peritoneum is an important target to enable long-term PD therapy in patients with end-stage renal disease. We previously showed that neutralization of the membrane complement regulators (CRegs) Crry and CD59 in rat peritoneum provokes development of acute peritoneal injury due to uncontrolled complement activation. C5a is a key effecter molecule of the complement system released during acute inflammation. Control of C5a has been proposed as a strategy to suppress inflammatory reactions and, because peritoneal injury is accompanied by inflammation, we hypothesized that C5a targeted therapy might be an effective way to suppress peritoneal injury. In the present study we used an established acute peritonitis model induced by neutralization of CRegs to investigate the effects on acute peritoneal injury of inhibiting C5a. Intravenous administration of an anti-C5a complementary peptide (AcPepA) up to 4 h after induction of injury significantly and dose-dependently prevented accumulation of inflammatory cells and reduced tissue damage in the model, accompanied by decreased C3b deposition. We show that C5a contributed to the development of peritoneal injury. Our results suggest that C5a is a target for preventing or treating peritoneal injury in patients undergoing prolonged PD therapy or with infectious complications.

Guideline for hereditary angioedema (HAE) 2010 by the Japanese Association for Complement Research - secondary publication.

This guideline was provided by the Japanese Association for Complement Research targeting clinicians for making an accurate diagnosis of hereditary angioedema (HAE), and for prompt treatment of the HAE patient in Japan. This is a 2010 year version and will be updated according to any pertinent medical advancements.

Endothelin receptor antagonist attenuates oxidative stress in a neonatal sepsis piglet model.

BACKGROUND: Oxidative stress (oxidant-antioxidant imbalance) plays an important role in the pathophysiology of neonatal sepsis. This study evaluated whether an antisense peptide endothelin receptor antagonist, ETR-P1/fl, could attenuate oxidative stress in a neonatal sepsis model. METHODS: A total of 18 3-d-old piglets were anesthetized and mechanically ventilated. Six piglets received cecal ligation and perforation (CLP group) for induction of sepsis. Six piglets also received continuous infusion (0.05 mg/kg/h) of ETR-P1/fl 30 min after CLP (ETR-P1/fl group). Six piglets received a sham operation. Serum total hydroperoxide (TH), biological antioxidant potentials (BAPs), oxidative stress index (OSI, calculated as TH/BAP), interleukin (IL)-6, serum glutamic oxaloacetic transaminase (GOT), and creatinine were measured before CLP and at 1, 3, and 6 h after CLP. RESULTS: CLP evoked a state of shock resulting in elevated TH, OSI, and IL-6 levels. ETR-P1/fl administration after CLP resulted in lower serum TH at 1 and 3 h after CLP, OSI at 1 and 3 h after CLP, IL-6 at 1 and 3 h after CLP, and GOT at 3 and 6 h after CLP as compared with the CLP group. CONCLUSION: ETR-P1/fl treatment significantly attenuated the elevation of serum oxidative stress markers (TH and OSI), IL-6, and GOT in a progressive neonatal sepsis CLP model.

Estrogen receptor α and ß differentially mediate C5aR agonist evoked Ca2+-influx in neurons through L-type voltage-gated Ca2+ channels.

Complement C5a is associated primarily with inflammation. The widespread expression of its receptors, C5aR and C5L2 in neuronal cells, however, suggests additional regulatory roles for C5a in the CNS. C5aR agonist (PL37-MAP) evokes Ca(2+)-influx in GT1-7 neuronal cell line and the Ca(2+)-influx is regulated by estradiol. In the present study, we examined further the mechanism of Ca(2+)-influx and the contribution of the two estrogen receptor (ER) isotypes, ERα and ERß, to estrogenic modulation of intracellular Ca(2+)-content. GT1-7 neurons were treated with isotype selective ER agonists for 24h then C5aR agonist evoked Ca(2+)-responses were measured by Ca(2+)-imaging. Transcriptional changes were followed by real-time PCR. We found that not only estradiol (100 pM), but the ERα selective agonist PPT (100 pM) enhanced the PL37-MAP-evoked Ca(2+)-influx (E2: 215%, PPT: 175%, compared to the PL37-MAP-evoked Ca(2+)-influx). In contrast, the ERß selective agonist DPN (100 pM) significantly reduced the Ca(2+)-influx (32%). Attenuated Ca(2+)-response (25%) was observed in Ca-free environment and depletion of the Ca(2+)-pool by CPA eliminated the remaining elevation in the Ca(2+)-content, demonstrating that the majority of Ca(2+) originated from the extracellular compartment. L-type voltage-gated Ca(2+)-channel (L-VGCC) blocker nifedipine abolished the Ca(2+)-influx, while R-type Ca(2+)-channel blocker SNX-482 had no effect, exemplifying the predominant role of L-VGCC in this process. Acute pre-treatments (8 min) with ER agonists did not affect the evoked Ca(2+)-influx, revealing that the observed effects of estrogens were genomic. Therefore, we checked estrogenic regulation of C5a receptors and L-VGCC subunits. ER agonists increased C5aR mRNA expression, whereas they differentially regulated C5L2. Estradiol decreased transcription of Ca(v)1.3 L-VGCC subunit. Based on these results we propose that estradiol may differentially modulate C5a-induced Ca(2+)-influx via L-VGCCs in neurons depending on the expression of the two ER isotypes.

Membrane complement regulators protect against fibrin exudation increases in a severe peritoneal inflammation model in rats.

Peritonitis and the rare sequela of encapsulating peritoneal sclerosis (EPS) are serious problems in patients on peritoneal dialysis therapy. Chronic and persistent peritoneal injuries may be a risk factor of EPS. We previously reported that a chronic, proliferative peritonitis developed when zymosan was administered intraperitoneally following scraping injury of rat peritoneum (Mizuno M, Ito Y, Hepburn N, Mizuno T, Noda Y, Yuzawa Y, Harris CL, Morgan BP, Matsuo S. J Immunol 183: 1403-1412, 2009). Peritoneal membrane complement regulators (CRegs), especially Crry and CD59, protected from injury by inhibiting local complement activation, suggesting that CRegs play important roles in maintaining homeostasis in rat peritoneum. Here, we investigated roles of complement in the development of EPS by neutralizing CReg function with monoclonal antibodies (MAbs). Proliferative peritonitis was induced by scraping the peritoneum, followed by daily intraperitoneal administration of zymosan. When either Crry or CD59 alone was neutralized by MAb, the tissue injuries were not significantly changed compared with rats without neutralizing MAb. When both Crry and CD59 were neutralized in this model, severe fibrin exudation was observed on the peritoneal surface on day 5, accompanied by inflammatory cell infiltration, resembling the early stages of development of EPS. Dense peritoneal deposition of C3 fragments and membrane attack complex were observed, along with the fibrin exudates. Intravenous administration of cobra venom factor, which profoundly activates complement, further enhanced these pathological changes. Our results show that complement activation in injured peritoneum drives peritoneal inflammation, and that enhancement of complement activation by inhibiting CReg and/or enhancing systemic activation contributes to the initiation of EPS; therefore, anti-complement agents might be of therapeutic value in humans for the treatment of EPS.

Novel complementary peptides to target molecules.

We generated an evolutionary computer program that generates complementary peptide (C-pep) sequences, with the potential to interact with a target peptide, by comparing several physico-chemical parameters of each pair of the complementary peptides being analyzed. We generated C-peps to target several molecules. About 30% of synthesized C-peps interfered with the function of their targets. C5a stimulates generation of TNFα and other inflammatory cytokines. Inhibition of C5a should be effective against sepsis, which impairs the status of cancer-bearing patients. One of the inhibitory C-peps of C5a, termed AcPepA, was effective in Cynomolgus monkeys intravenously infused with a lethal dose of bacterial LPS (4 mg/kg) destined to die. The monkeys were rescued by intravenous administration of 2 mg/kg/h of AcPepA. The excellent therapeutic effect of AcPepA is likely to be due to restriction of high mobility group box 1 (HMGB1) surge induced by the effect of C5a on C5L2, which is the second C5a receptor, since the released HMGB1 has the capacity to stimulate TLR4 as an endogeneous ligand resulting in further activation of inflammatory cells to release inflammatory cytokines forming a positive feedback circuit of inflammation.

Serum concentrations of complement anaphylatoxins and proinflammatory mediators in patients with 2009 H1N1 influenza.

Anaphylatoxins (C5a, C4a, and C3a) are fragments of activated complement and are leading mediators of the inflammatory response for controlling viral infection. However, an excessive response may increase the severity of infectious diseases. Serum concentrations of proinflammatory mediators, including cytokines, high-mobility group box 1 and anaphylatoxins, were measured in pediatric 2009 H1N1 influenza patients in order to investigate the pathology of this new influenza. The concentrations of all three anaphylatoxins were significantly enhanced by 2009 H1N1 influenza infection. However, there were no significant differences in anaphylatoxin concentrations between 2009 H1N1 influenza patients with and without severe complications during the early stages of the disease. C3a concentrations dropped significantly during the recovery phase, whereas there were no significant differences between the acute and recovery phases in C5a and C4a concentrations. There was a correlation between C5a and IL-2. C4a was associated with IL-1ra, eotaxin, MCP-1, PDGFbb, and VEGF. C3a was correlated with IL-2 and IFN-γ. Taken together, these findings indicate that complement activation occurs in patients infected with 2009 H1N1 influenza virus and demonstrate that anaphylatoxins are involved in increased production of proinflammatory mediators in this new influenza.

Specific collaboration between rat membrane complement regulators Crry and CD59 protects peritoneum from damage by autologous complement activation.

BACKGROUND: The peritoneal cavity is isolated from the outside and is usually a sterile environment. Patients on peritoneal dialysis (PD) have PD fluid (PDF) infused into the peritoneal cavity. We previously showed that unregulated complement activation could contribute to the development of peritoneal inflammation in yeast peritonitis in PD therapy. In that situation, suppression of local complement activation is essential to protect the host from further injury. The membrane complement regulators (CRegs), Crry, CD55 and CD59, are expressed in the rat peritoneum, especially along the mesothelial cell layer. METHODS: We investigated CRegs' functional roles in the peritoneal cavity using blocking mAb against each CReg and complement activation in different PDFs. RESULTS: Blockade of any single CReg did not cause spontaneous peritoneal injury in rat. Combined blockade of Crry and CD59 induced focal peritoneal tissue injury and heavy accumulation of inflammatory cells with peritoneal edema at 24 h. Deposits of C3 and C5b-9 were found on the peritoneal surface after combined blocking of Crry and CD59. Systemic complement depletion by cobra venom factor abrogated these inflammatory changes. When combined blockade of Crry and CD59 was performed with PDF of different pH and glucose concentration in rats, the peritoneal injuries were enhanced with lower pH and higher glucose concentration. These results were confirmed by in vitro experiments using primary rat mesothelial cell culture. CONCLUSIONS: Rat CRegs, Crry and CD59, specifically collaborate to control complement activation in rat peritoneum. During PD, impairment of CReg might contribute to the development of severe peritoneal inflammation.

Endothelin receptor antagonist attenuates inflammatory response and prolongs the survival time in a neonatal sepsis model.

PURPOSE: To evaluate effects of endothelin receptor antagonist ETR-P1/fl in a neonatal sepsis model. METHOD: Eighteen anesthetized and mechanically ventilated 3-day-old piglets were divided into three groups. Six piglets received cecal ligation and perforation (CLP group). Six piglets were administrated a continuous infusion of ETR-P1/fl (0.05 mg/kg/h), an antisense homology box-derived peptide with an endothelin A receptor antagonist effect, starting 30 min after CLP (ETR-P1/fl group). Six piglets acted as the sham group. Mean arterial pressure (MAP), heart rate, cardiac output, arterial blood gas, body temp (BT), serum nitrite and nitrate (NOx), tumor necrosis factor (TNF)-α, and high-mobility group box 1 (HMGB-1) were measured before CLP and at 1, 3, 6, and 9 h after CLP. RESULTS: Cecal ligation and perforation exposure evoked a state of shock and showed deteriorated cardiac output, pulmonary hypertension, decreased MAP, low oxygen saturation, and base excess (BE) with elevated TNF-α, NOx, and HMGB1. ETR-P1/fl administration resulted in higher MAP at 6 and 9 h after CLP, less negative BE, lower mean pulmonary arterial pressure (mPAP)/MAP ratio at 9 h after CLP, and lower TNF-α, NOx, and HMGB-1 compared to the CLP group. BT showed no differences between the groups. Survival time in the ETR-P1/fl group was longer than in the CLP group (18.9 ± 2.3 h vs. 9.0 ± 0.8 h, p < 0.01). CONCLUSIONS: ETR-P1/fl treatment significantly attenuated the elevation of NOx, TNF-α, and HMGB-1, which improved the systemic hypotension, pulmonary hypertension, and blood gases, thereby causing improvement of survival time in a progressive neonatal sepsis CLP model.

A complement-dependent cytotoxicity-enhancing anti-CD20 antibody mediating potent antitumor activity in the humanized NOD/Shi-scid, IL-2Rγ(null) mouse lymphoma model.

Engineering the Fc region of monoclonal antibodies (mAb) in order to enhance effector functions such as antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity (CDC) is likely to a be promising approach for next-generation mAb therapy. Here, we report on such an antibody, 113F, a novel CDC-enhancing variant of rituximab, and determine the tumor-associated factors influencing susceptibility to 113F-induced CDC. The latter included the quantity of complement inhibitors present, such as CD55 and CD59. We report that compared to rituximab, 113F mediated highly enhanced CDC against primary CD20-expressing lymphoma cells in vitro. Currently, a major problem in the field of immunotherapy research is the lack of suitable small animal models to evaluate human CDC in vivo. Therefore, we established a novel human tumor-bearing NOD/Shi-scid, IL-2Rγ(null) mouse model, in which human complement functions as the CDC mediator. We demonstrated that rituximab exerted significant antitumor effects via human CDC in this humanized mouse. The finding of specific localization of human C1q on CD20-expressing tumor cell membranes was consistent with the observation that human CDC indeed contributed to the antitumor effect in this model. Moreover, 113F exerted significantly more potent antitumor effects than rituximab in this in vivo model. The detection of more abundant dense signals from C1q using 113F compared to rituximab was consistent with the concept that this reagent represented a CDC-enhancing mAb. In the near future, the efficacy of this type of CDC-enhancing antibody will be determined in clinical trials in humans.

Procarboxypeptidase R deficiency causes increased lethality in concanavalin A-induced hepatitis in female mice.

Carboxypeptidase R (CPR), also known as thrombin-activatable fibrinolysis inhibitor (TAFI), is an enzyme generated by proteolytic cleavage of its zymogen (proCPR). CPR removes the C-terminal arginine from inflammatory peptides such as C3a and C5a, bradykinin, enkephalin, and the thrombin-cleaved N-terminal fragment osteopontin (cleaved N-OPN). In the mouse model of concanavalin A (Con A)-induced immune-mediated fulminating hepatitis, cleaved N-OPN is one of the important peptides that induce the production of chemokines or cytokines. In the current study using proCPR deficient mice, we showed that injection of Con A into the mouse tail vein can induce a significantly higher lethality in proCPR-deficient female but not in male mice. Furthermore, a lack of CPR activity increased serum macrophage inflammatory protein-2 (MIP-2) and high-mobility group box 1 (HMGB1) levels after Con A injection. These in vivo findings suggest that CPR helps to protect against Con A-induced hepatitis.

TbUNC119 and its binding protein complex are essential for propagation, motility, and morphogenesis of Trypanosoma brucei procyclic form cells.

Flagellum-mediated motility of Trypanosoma brucei is considered to be essential for the parasite to complete stage development in the tsetse fly vector, while the mechanism by which flagellum-mediated motility is controlled are not fully understood. We thus compared T. brucei whole gene products (amino acid sequence) with Caenorhabditis elegans UNC (uncoordinated) proteins, in order to find uncharacterized motility-related T. brucei genes. Through in silico analysis, we found 88 gene products which were highly similar to C. elegans UNC proteins and categorized them as TbCEUN (T. brucei gene products which have high similarity to C. elegansUNC proteins). Approximately two thirds of the 88 TbCEUN gene products were kinesin-related molecules. A gene product highly similar to C. elegans UNC119 protein was designated as TbUNC119. RNAi-mediated depletion of TbUNC119 showed no apparent phenotype. However, knock-down analysis of both TbUNC119 and its binding protein (TbUNC119BP) which was found by yeast two-hybrid analysis showed characteristic phenotypes, including reduced motility, morphological change (extended cell shape), and cellular apoptosis. Based on the observed phenotypes, possible function of the TbUNC119 and TbUNC119BP is discussed.

Attenuation of cross-talk between the complement and coagulation cascades by C5a blockade improves early outcomes after intraportal islet transplantation.

BACKGROUND: Complement 5a factor (C5a) elicits a broad range of proinflammatory effects, including chemotaxis of inflammatory cells and cytokine release. C5a is also linked to the coagulant activity in autoimmune diseases. Therefore, C5a most likely plays a crucial role in the instant blood-mediated inflammatory reaction. METHODS: Intraportal transplantation of 2.5 islet equivalents/g of syngeneic rat islet grafts was performed in two groups of streptozotocin-induced diabetic rats: controls and C5a inhibitory peptide (C5aIP)-treated group. RESULTS: The thrombin-antithrombin complex was significantly suppressed in the C5aIP group (P=0.003), and both the curative rate and the glucose tolerance were significantly improved in the C5aIP group (P<0.05 and P<0.005, respectively). Expression of tissue factor on granulocytes in recipient livers was up-regulated 1 h after islet infusion (P<0.0001), which was significantly suppressed by C5aIP (P<0.005). However, C5aIP was unable to regulate tissue factor expression on isolated islets. Furthermore, no differences were detected between the groups, regarding infiltration of CD11b-positive cells and deposition of C5b-9 on the islet grafts. CONCLUSIONS: These data suggest that C5aIP attenuates cross-talk between the complement and coagulation cascades through suppressing up-regulation of tissue factor expression on leukocytes in recipient livers but not on islet grafts, a process leading to improvement in islet engraftment. Therefore, C5aIP in combination with conventional anticoagulants could be a strong candidate strategy to control the instant blood-mediated inflammatory reaction induced in clinical islet transplantation.

[Refractory acquired hemophilia A successfully treated with CVP].

A 44-year-old woman was referred to our hospital for massive subcutaneous and intramuscular hemorrhage. Prolonged APTT, low factor VIII activity and factor VIII inhibitor with high titer (30 BU/ml) were observed, confirming the diagnosis of acquired factor VIII inhibitor. Although treated with methylprednisolone, she relapsed after a month. Subsequently, she was treated with three courses of CVP (cyclophosphamide, vincristine, prednisolone) therapy, combined with recombinant activated factor VII. The activity of factor VIII was normalized one week after starting CVP, and the inhibitor disappeared 13 months later. She has maintained complete remission for 26 months without recurrence to date. CVP therapy is very effective against refractory acquired factor VIII inhibitor.

Low CR1 (C3b receptor) level on erythrocytes is associated with poor prognosis in hemodialysis patients.

BACKGROUND: Erythropoietin in patients under dialysis treatment for renal failure is low which induces anemia. Treatment with recombinant erythropoietin (rEPO) has been used routinely as a supplement treatment for these patients. Immune complexes (IC) react with complement and bind to CR1 on erythrocytes (E-CR1), and are transported to the liver and/or spleen where IC removal and degradation occurs. The erythrocytes then return to circulation where they bind to additional IC. There are some patients whose E-CR1 expression is low with chronic anemia in spite of rEPO treatment. We hypothesized that in hemodialysis (HD) patients altered host defense against infection is associated with low levels of E-CR1. We examined if low E-CR1 in dialysis patients constitutes a risk factor for reduced host defense and poor outcome. METHODS: In 95 HD patients, E-CR1 was quantified using a monoclonal E-CR1 antibody and FACS analysis followed by clinical course studies for 5 years. RESULTS: The patients were divided into three groups by E-CR1 level. Percent survival for the low E-CR1 group (53.3%) was significantly lower than the high E-CR1 group (86.4%) (p < 0.01). There were more hepatitis C virus-positive patients within the low E-CR1 group (27.3%) than in the high E-CR1 group (4.7%) (p < 0.05). Furthermore, 10 patients with the lowest E-CR1 levels had severe complications, notably infection at an arteriovenous fistula. CONCLUSION: A reduced E-CR1 level might be a risk factor for reduced host defense and can be used as a predicting factor for poor prognosis in a HD patient.