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Background. Antibody-mediated rejection (AMR) is a major cause of kidney allograft failure. Its molecular mechanisms are multifaceted and may include a role of complement activation via the classical pathway. Here, we investigated whether noninvasive complement monitoring adds predictive power to the diagnosis of AMR in the setting of donor-specific antibody (DSA) positivity. Methods. In this cross-sectional study, 741 kidney transplant recipients with stable graft function ≥180 days posttransplantation were screened for the presence of human leukocyte antigen (HLA) alloantibodies. Eighty-three of 111 DSA-positive recipients underwent protocol biopsies and were tested for blood and urinary levels of complement proteins (C1q, C4, C3) and activation products (C4d, C3a, C5a, C5b-9). Results. Forty-seven recipients were diagnosed with AMR, and 21 were C4d-positive. While biopsy-confirmed AMR (and C4d) associated with DSA-binding strength (IgG mean fluorescence intensity of the immunodominant DSA versus AMR; area under the receiver operating characteristic curve: 0.76), tested complement markers did not have any predictive value for rejection (area under the receiver operating characteristic curve: 0.49–0.56). There were, however, tight correlations between complement activation products in urine and protein/creatinine ratio (ρ = 0.44–0.64; P < 0.001). Analysis of death-censored graft survival over a median of 60 months revealed no independent associations with levels of complement markers in blood or urine. Conclusions. Complement patterns in blood and urine failed to identify AMR in late biopsies and may have no relevant diagnostic value in this particular context.

Rationale: This article describes a child with a life-threatening multiorgan failure with disseminated intravascular coagulation (DIC) and massive complement consumption. To our knowledge this therapeutic approach was for the first time effectively applied in a pediatric patient. Patient concerns: A 14-month-old boy was presented with a severe, rapidly progressing, life-threatening disease because of sudden onset of fever, hemathemesis, hematuria, and bloody diarrhoea alongside fast spreading hematomas and general corporeal edema. Diagnosis: The most plausible diagnosis in our patient is Clostridium difficile sepsis-induced thrombotic microangiopathy alongside with DIC and consumption coagulopathy. The diagnosis was confirmed by positive C difficile bacteria strain in coproculture, clinical, and laboratory tests affirming DIC and global complement activation and consumption. Interventions: The patient was treated with antibiotics (Metronidazole, Vancomycin), plasmapheresis, dialysis, methylprednisolone, mycophenolate mofetil, and Eculizumab. Outcomes: The child is in fair overall condition in a 2 year follow-up with no complications save chronic renal failure. Lessons: In rare cases of sepsis with massive complement consumption, a case-sensitive Eculizumab therapy may be at least considered after the resolution of life-threatening multiorgan failure. The application of this drug can be performed only after sepsis induced disease is put under control. A fast withdrawal of Eculizumab after control of massive complement consumption is recommended to prevent triggering of second sepsis reactivation.

Background and Purpose—Recently we found that the incidence of restenosis after carotid endarterectomy was significantly higher in patients homozygous for the normal genotype of mannose-binding lectin (MBL2) than in with patients withMBL2variant genotypes. Several growth factors are also known to contribute to restenosis. Therefore, we investigated whether early postoperative changes in serum vascular endothelial growth factor (VEGF), epidermal growth factor (EGF), and platelet-derived growth factor (PDGF) concentrations andMBL2genotypes interact in the development of restenosis.Methods—Eighty-two patients who underwent carotid eversion endarterectomy and were followed up by carotid duplex scan sonography for 14 months were studied. Growth factors were measured preoperatively and 4 days after surgery.Results—Pronounced significant increases in both VEGF and PDGF predicted restenosis but only in patients who were homozygous for the normalMBL2genotype. In this group, the adjusted odds ratios of restenosis at 14 months in patients with high versus low early VEGF and PDGF increases were 27.73 (2.42 to 317.26) and 9.23 (1.45 to 58.70), respectively.Conclusions—These findings indicate that the development of restenosis depends on both complement activation regulated by theMBL2gene and pathologic processes leading to enhanced production of VEGF and PDGF during the very early postoperative period.

Background and Purpose—Mannose-binding lectin (MBL) is thought to influence the pathophysiology of cardiovascular disease by decreasing the risk of advanced atherosclerosis and by contributing to enhanced ischemia reperfusion injury. Thus, we investigated the role of MBL in restenosis after eversion endarterectomy in patients with severe carotid atherosclerosis.Methods—In a prospective study, 123 patients who underwent carotid endarterectomy were followed-up by carotid duplex scan (CDS) sonography for 14 months. In a retrospective study, we examined 17 patients and 29 patients, respectively, who had or had not at least 50% restenosis 29 months after carotid eversion endarterectomy. MBL genotypes were analyzed by a polymerase chain reaction-based method, and MBL serum concentrations were measured.Results—In the prospective study in the patients homozygous for the normal MBL genotype, CDS values were significantly higher after 14 months of follow-up compared with the values measured 6 weeks after surgery (PP=0.007).Conclusions—These results indicate that reoccurrence of stenosis after carotid endarterectomy is partially genetically determined and imply that MBL contributes significantly to the pathophysiology of this condition.

Background— Several recent studies have indicated an association between key inflammatory mediators and atherosclerotic diseases. We evaluated whether high levels of antibodies against heat shock proteins and cholesterol (ACHA) predicted cardiovascular (CV) events. Methods and Results— We used blood samples from the Heart Outcomes Prevention Evaluation (HOPE) study to conduct a nested case-control study of 386 cases with CV events and 386 age- and sex-matched HOPE study controls without events. We explored the relationship between anti-hsp antibodies, ACHA, and subsequent outcomes (incident myocardial infarction, stroke, or CV death) during a mean follow-up of 4.5 years using conditional logistic regression. High levels of anti-hsp65 antibodies (≥90th percentile) predicted CV events (OR, 2.1; 95% CI, 1.2 to 3.9, P =0.01). Anti-hsp60 antibodies did not predict any event type, whereas incident stroke developed significantly less frequently in patients with high ACHA levels. Anti-hsp antibodies and ACHA did not correlate with inflammatory (fibrinogen, C-reactive protein, interleukin-6, intracellular adhesion molecule-1) or infectious markers ( C pneumoniae or cytomegalovirus antibodies). Anti-hsp65 antibodies (≥90th percentile) and fibrinogen (highest tertile) had a strong joint effect: patients with high concentrations of both had more CV events (OR, 5.5; 95% CI, 1.8 to 17.5, P =0.004) than patients with low levels of both. A similar joint effect (OR, 2.7; 95% CI, 1.3 to 5.7, P =0.01) was found for high levels of anti-hsp65 and presence of cytomegalovirus antibodies. Conclusions— Serum antibodies to hsp65 were associated with subsequent CV events in this study of high-risk patients, independent of conventional cardiovascular risk factors and other inflammatory markers.

Background and Purpose —A strong correlation exists between the intensity of atherosclerotic alterations in different arteries. Marked differences exist, however, in the age and sex distribution and risk factors for coronary heart disease (CHD) and cerebrovascular disease (CVD). We therefore performed genetic and immunologic studies in patients with CVD. Methods —We studied 292 patients with CVD (stroke or transient ischemic attack) and as control either 198 healthy blood donors and 485 healthy elderly (aged >60 years) people (genetic study) or 94 blood donors aged 45 to 60 years and 49 healthy elderly (aged >60 years) people (anti–heat-shock protein [hsp] measurements). Allele frequencies of 3 genes (C4A, C4B, and C3) encoding proteins of the complement system were determined by electrophoresis and immunofixation. Serum concentration of autoantibodies against 60-kDa heat-shock protein (anti-hsp60) was measured by the enzyme-linked immunosorbent assay method. Results —Marked differences were observed between CVD patients and controls in the genetic studies. In the CVD patients aged >60 years, the frequency (11.3%) of the deficient allele of the C4B gene (C4B*Q0) was significantly ( P =0.0003) higher than that of the healthy controls (5.4%). By contrast, in the group aged 45 to 60 years, the frequency of the C4B*Q0 allele was lower in patients than in controls. Serum concentration of anti-hsp60 in the CVD patients did not differ from control values. Conclusions —In previous studies C4B*Q0 frequency was reported to be higher in CHD patients aged 45 to 60 years than in aged-matched controls. Moreover, high anti-hsp60 levels were found in CHD patients. These findings contrast with our present report of lower frequency of C4B*Q0 in CVD patients. Therefore, genetic and immunologic factors may at least partly explain the differences between the natural history and risk factors of CHD and CVD.

Objective To study the mechanism of the complement-mediated antibody-dependent enhancement (C'-ADE) of HIV infection which may play a significant role in the progression of HIV-disease. Methods In vitro complement activating and complement-mediated HIV-infection enhancing abilities of three human anti-gp41 monoclonal antibodies (MAb) were tested. C'-ADE was estimated using HIV-1IIIB and CR2 (CD21)-carrying MT-4 target cells. Normal human serum (NHS), purified C1q, C1q-deficient (C1qD) and C2-deficient (C2D) human sera were applied as complement sources. Results All MAb mediated increased C1q binding to solid-phase gp41. All MAb had a marked dose-dependent and strictly complement-mediated HIV-infection enhancing effect. Mixtures of the MAb with purified C1q also significantly increased HIV-1 infection. C1qD serum had a markedly lower enhancing effect than NHS, which could be raised to normal level by addition of purified C1q. Pretreatment of the target cells with anti-CR2 antibodies only partially inhibited the enhancing effect of the MAb plus normal human serum. Conclusion These novel findings indicate that besides the well-known facilitation of entry of HIV-1 by the interaction between virus-bound C3 fragments and CR2 present on the target cells, fixation of C1q to intact virions also results in an enhanced productive HIV-1 infection in the MT-4 cell cultures.