Eric Wagner

Therapeutic potential of complement modulation

The complement system is an essential component of innate immunity that has been more recently recognized as an unexpected player in various pathological states. These include age-related macular degeneration, atypical haemolytic uraemic syndrome, allergy, foetal loss, and axonal and myelin degradation after trauma. Its importance has also been recognized in physiological processes including haematopoietic stem cell homing to the bone marrow, liver regeneration and modulation of adaptive immune responses. Although the complement system has long been known to be involved in autoimmune and inflammatory diseases, few agents that target the complement system are currently approved for clinical use. However, renewed interest in modulating this system in various pathological conditions has emerged, and several agents are now in development.

Functional C1-inhibitor diagnostics in hereditary angioedema: assay evaluation and recommendations.

Hereditary angioedema (HAE) is an autosomal dominant disease characterized by recurrent episodes of potentially life-threatening angioedema. The most widespread underlying genetic deficiency is a heterozygous deficiency of the serine protease inhibitor C1 esterase inhibitor (C1-Inh). In addition to low C4 levels, the most important laboratory parameter for correct diagnosis of HAE or angioedema due to acquired C1-Inh deficiency is reduced C1-Inh function (fC1-Inh). No direct recommendations about the assays for fC1-Inh or sample handling conditions are available, although this would prove especially useful when a laboratory first starts to offer assays on fC1-Inh for HAE diagnosis. In the present study we evaluated the performance of fC1-Inh assays in the 15 different laboratories that are specialised in HAE diagnostics and assessed inter-laboratory variation with each laboratory using their own assays and standards. A double-blind survey was conducted using plasma/serum samples from healthy donors and HAE patients and the uniformity of HAE diagnosis was evaluated. It can be concluded that the diagnosis of fC1-Inh deficiency was made correctly in most cases in this survey. We can recommend the chromogenic assay for the determination of fC1-Inh, while the complex ELISA needs further investigation.

Assessment of cord blood unit characteristics on the day of transplant: comparison with data issued by cord blood banks

BACKGROUND:  Selection of a cord blood (CB) unit for allogeneic transplantation relies on graft characterization results provided by cord blood banks (CBBs). The goal was to compare the graft characterization results obtained upon thawing and washing to those provided by CBBs at selection.

2013 Banff Criteria for Chronic Active Antibody-Mediated Rejection: Assessment in a Real-Life Setting

Significant changes in the criteria for chronic active antibody‐mediated rejection (CAABMR) were made in the Banff 2013 classification. These modifications expanded the number of patients diagnosed with CAABMR, with undetermined clinical significance. We compared the 2007 and 2013 criteria for the composite end point of death‐censored graft failure or doubling of serum creatinine in 123 patients meeting the criterion related to the morphologic evidence of chronic tissue injury. In all, 18% and 36% of the patients met the 2007 and 2013 criteria, respectively. For the criterion related to antibody interaction with endothelium, only 25% were positive based on the 2007 definition compared with 82% using the 2013 definition. Cox modeling revealed that a 2013 but not a 2007 diagnosis was associated with the composite end point (adjusted hazard ratio 2.5 [95% confidence interval (CI) 1.2–5.2] vs. 1.6 [95% CI 0.7–3.8], respectively). The 2013 criterion based on both the C4d score and the glomerulitis plus peritubular capillaritis score (g+ptc) was more strongly associated with the end point than the 2007 criterion based only on C4d; however, when dissected by component, only the C4d component was significant. The association with clinical outcomes improved with the 2013 criteria. This is related to the new C4d threshold but not to the g+ptc ≥2 component.

Donor-specific antibodies require preactivated immune system to harm renal transplant

Highlights • Pretransplant DSA have a deleterious impact on graft survival only in the presence of high pretransplant serum levels of sCD30.• The majority of patients with pretransplant DSA might be transplanted safely without special pretreatment measures. Kidney transplantation in the presence of donor-specific HLA antibodies (DSA) is associated with a high failure rate due to antibody-mediated rejection. Many centers avoid transplantations if DSA are present. Others perform such transplantations after removal of DSA by apheresis under potent immunosuppression. We provide strong evidence that DSA positive recipients reject their grafts at a high rate only if the immune activation marker sCD30 is also high, suggesting that T-cell help from an activated immune system is necessary for pretransplant DSA to exert a deleterious effect on the graft. High-risk patients with DSA and sCD30 may benefit from special treatment measures. The presence of DSA alone may not be deleterious.

L‐Asparaginase lowers plasma antithrombin and mannan‐binding‐lectin levels: Impact on thrombotic and infectious events in children with acute lymphoblastic leukemia

L‐asparaginase, a key therapeutic agent in the management of patients with acute lymphoblastic leukemia (ALL), dramatically impairs hepatic protein synthesis. We investigated the effects of prolonged exposure to L‐asparaginase on antithrombin (AT), fibrinogen and mannan‐binding‐lectin (MBL) levels, and on the occurrence of thrombotic events (TE) and febrile neutropenia episodes (FN) in pediatric patients.

Higher calcineurin inhibitor levels predict better kidney graft survival in patients with de novo donor‐specific anti‐HLA antibodies: a cohort study

The development of de novo anti‐HLA donor‐specific antibodies (dnDSA) is associated with poorer outcomes in kidney transplant recipients. Despite this, antibody screening post‐transplant is not widespread, largely because the optimal management of patients with dnDSA remains undetermined. We hypothesized that in this population, calcineurin inhibitor blood levels would be an independent predictor of graft loss. We analyzed a cohort of unsensitized patients for whom anti‐HLA antibody screening was performed prospectively post‐transplant. During the screening period between January 2005 and April 2016, 42 patients developed dnDSA. There was no difference in the clinical characteristics or the histological scores of patients biopsied for clinical indication versus those biopsied solely due to detection of dnDSA. Cox modeling revealed a strong relationship between mean tacrolimus levels following dnDSA detection and graft loss, with a hazard ratio of 0.49 (95% CI, 0.33–0.75), which persisted following adjustment for established independent predictors (HR, 0.52, 95% CI, 0.30–0.89). Kaplan–Meier analysis by tertiles of tacrolimus levels and receiver operating curve analysis concurred to show that a threshold of 5.3 ng/ml could be predictive of graft loss. These data suggest that anti‐HLA antibody monitoring post‐transplant could guide maintenance immunosuppression and improve graft outcomes.

Examination of genetic variants involved in generation and biodisposition of kinins in patients with angioedema

BackgroundAngioedema (AE) is idiopathic in the majority of cases. We studied patients with AE for genetic variants of proteins involved with bradykinin generation and biodisposition.MethodsOne hundred sixty one patients with AE were recruited at a university hospital clinic. Patients were categorized according to the proposed pathogenesis of AE: low C1 inhibitor (C1-INH) and C4 levels, autoimmune disease, cancer, angiotensin-converting enzyme (ACE) inhibitor-induced, nonsteroidal antiinflammatory drug (NSAID)-induced, or idiopathic. In addition, each patient had a blood sample analyzed for a complement profile and enzymes (C1-INH and C4). Fifty-two of the patients were tested for genetic variants in factor XII, plasminogen-activator inhibitor-1 (PAI-1), ACE, and aminopeptidase P (APP).ResultsThe cause of angioedema was identified in 59/161 (37%) of the cases: 3 (2%) patients had a low plasma C1-INH and C4; 20 (12%) were ACE inhibitor-induced; 12 (7%) were associated with autoimmune disorders; 7 (4%) were associated with malignancy; and 17 (11%) were associated with NSAIDs. In the remaining 102 (63%) patients the cause of angioedema was idiopathic. Of 52 patients with genetic analysis, 13 (25%) had a genetic variant in APP, 10 (19%) in ACE, 13 (25%) in PAI-1, and 0 in Factor XII.ConclusionsIn addition to related diseases and medications causing AE, certain genetic variants encoding proteins involved in bradykinin generation and/or catabolism pathways may be involved in the pathogenesis of AE.

The isolated human umbilical vein as a bioassay for kinin-generating proteases: An in vitro model for therapeutic angioedema agents

AIMS The isolated human umbilical vein is a robust contractile bioassay for ligands of the bradykinin (BK) B2 receptor (B2R), also extendable to B1 receptor (B1R) pharmacology. We hypothesized that, as a freshly isolated vessel, it also contains traces of plasma proteins that may confer responses to exogenous proteases via the formation of kinins. MAIN METHODS Rings of human umbilical veins were mounted in organ baths containing Krebs buffer maintained at 37°C and purified proteases were introduced in the bathing fluid along with additional drugs/proteins that permit mechanistic analysis of effects. KEY FINDINGS The previously described contractile response to human recombinant tissue kallikrein (KLK-1, 1-10nM) is not influenced by metabolic inhibitors, suggesting its dependence on a preexisting reservoir of low molecular weight-kininogen (LK). Active plasma kallikrein (apK, ≤5nM) was inactive in fresh tissues, unless high molecular weight-kininogen (HK, 39-197nM) replenishment was applied. The effects of KLK-1 and HK+apK are abolished by pretreating tissues with icatibant, but not with tranexamic acid. C1-esterase inhibitor inhibited only HK+apK. Purified plasmin and neutrophil proteinase-3 produced small contractions in the presence of HK only, and tissue plasminogen activator, none. B1R stimulation was pharmacologically evidenced in response to KLK-1 if LK was supplied. SIGNIFICANCE The pharmacology of KLK-1 and HK+apK in the human isolated umbilical vein is essentially based on the activity of locally generated kinins and this assay models the inhibitory action of some therapeutic agents active in angioedema states. Proteases that indirectly generate kinins have little activity in the system.

Allogeneic dendritic cells stimulated with antibodies against HLA class II polarize naive T cells in a follicular helper phenotype

Follicular helper T cells (Tfh) are crucial for the production of high-affinity antibodies, such as alloantibodies, by providing the signals for B-cell proliferation and differentiation. Here, we demonstrate that human allogeneic dendritic cells (DC) stimulated with antibodies against HLA class II antigens preferentially differentiate human naive CD4+ T cells into Tfh cells. Following coculture with DCs treated with these antibodies, CD4+ T cells expressed CXCR5, ICOS, IL-21, Bcl-6 and phosphorylated STAT3. Blockade of IL-21 abrogated Bcl-6, while addition of the IL-12p40 subunit to the coculture increased CXCR5, Bcl-6, phosphorylated STAT3 and ICOS, indicating that they were both involved in Tfh polarization. We further phenotyped the peripheral T cells in a cohort of 55 kidney transplant recipients. Patients with anti-HLA-II donor-specific antibodies (DSA) presented higher blood counts of circulating Tfh cells than those with anti-HLA-I DSAs. Moreover, there was a predominance of lymphoid aggregates containing Tfh cells in biopsies from patients with antibody-mediated rejection and anti-HLA-II DSAs. Collectively, these data suggest that alloantibodies against HLA class II specifically promote the differentiation of naive T cells to Tfh cells following contact with DCs, a process that might appear in situ in human allografts and constitutes a therapeutic target.