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Background: The presence of anti-Beta 2 glycoprotein antibodies (aB2GP1) of IgA isotype is common in patients with functional impairment of the organs in which B2GP1 is elaborated. Pretransplant IgA aB2GP1 has been associated with increased risk of thrombosis in kidney and heart transplanted patients and has also been related with early mortality after heart transplantation. Circulating immune complexes between IgA and B2GP1 (B2A-CIC) have been described in the blood of patients positive for IgA aB2GP1 with thrombotic clinical symptoms. In kidney transplanted patients, B2A-CIC is a biomarker that predicts which patients IgA aB2GP1 positive are at risk of thrombosis events following kidney transplantation and may lead to early prophylactic treatment. The prevalence of B2A-CIC and its relation with outcomes after heart transplantation is not known. Methods: Follow-up study based on 151 consecutive patients who received a heart transplant. Autoantibodies and B2A-CIC were quantified in pre-transplant serum samples. Three groups of patients were followed-up for 2 years: Group-1, positive for IgA aB2GP1 and B2A-CIC ( N = 19). Group-2, only positive for IgA aB2GP1 ( N = 28). Group-0 (control group): IgA aB2GP1 negative ( N = 104). Results: Kaplan-Meir survival analysis showed that mortality in B2A-CIC positive was higher than group-0 at 3 months (HR:5.08; 95%CI: 1.36-19.01) and at 2 years (HR:3.82; 95%CI: 1.54-12.66). No significant differences were observed between group-2 and group-0. Multivariate analysis identified B2A-CIC as the most important independent risk factor for early mortality (OR = 6.12; 95% CI: 1.93-19.4). Post-transplant incidence of thrombosis was significantly higher in B2A-CIC positive patients than in the control group (OR: 6.42; 95%CI: 2.1-19.63). Multivariate analysis identified the presence of B2A-CIC (OR: 6.13; 95%CI: 2.1-19.63) and the pre-transplant habit of smoking actively (OR: 4.18; 95%CI: 1.35-12.94) as independent risk factor for thrombosis. The proportion of patients who had thrombotic events or died in the first trimester was significantly higher in group-1 (73.7%) than in group-0 (16.3%; p < 0.001) and in group-2 (39.3%; p = 0.02). Multivariate analysis identified B2A-CIC as the main independent risk factor for early outcomes (mortality or thrombosis) in the first 3 months after heart transplant (OR = 11.42, 95% CI: 1.69-9.68). Conclusion: B2A-CIC are a predictor of early mortality and thrombosis after heart transplant., (Copyright © 2019 Serrano, Morán, Martinez-Flores, Mancebo, Pleguezuelo, Cabrera-Marante, Delgado and Serrano.)

Background: Antiphospholipid syndrome (APS) is characterized by thrombosis and/or pregnancy morbidity with presence of anti-phospholipid antibodies (aPL). The APS classification criteria only consider the aPL of IgG/IgM isotype, however testing of aPL of IgA isotype is recommended when APS is suspected and consensus aPL are negative. IgA anti-βeta-2 glycoprotein-I (B2GP1) has been clearly related with occurrence of thrombotic events. Antibodies anti-B2GP1 of IgG/M isotypes recognize an epitope in Domain 1 (R39-G43), the epitopes that recognize IgA anti-B2GP1 antibodies are not well-identified. Aim: To determine the zones of B2GP1 recognized by antibodies of IgA isotype from patients with APS symptomatology and positive for IgA anti-B2GP1. Methods: IgA antibodies to Domain-1(D1) and Domain-4/5(D4/5) of B2GP1 (ELISA) and epitope mapping on oligopeptide arrays of B2GP1 were evaluated in sera from a group of 93 patients with at least one thrombotic and with isolated positivity for IgA anti-B2GP1 antibodies (negative for other aPL). Results: A total of 47 patients (50.5%) were positive for anti-D4/5 and 23(25%) were positive for anti-D1. When peptide arrays were analyzed, three zones of B2GP1 reactivity were identified for more than 50% of patients. The center of these zones corresponds to amino acids 140(D3), 204(D4), and 264(D5). The peptides recognized on D3 and D4 contain amino acid sequences sharing high homology with proteins of microorganism that were previously related with a possible APS infectious etiology. In the three-dimensional structure of B2GP1, the three peptides, as the R39-G43 epitope, are located on the right side of the molecule (L-shape). The left side (J-shape) does not bind the antibodies. Conclusions: Patients with thrombotic APS clinical-criteria, and isolated IgA anti-B2GP1 positivity appear to preferentially bind, not to the D1 or D4/5 domains of B2GP1, but rather to three sites in D3, D4, and D5. The sites on D3 and D4 were previously described as the target identified by human monoclonal antibodies derived from patients that were capable of inducing APS in animal models. The localization of these epitopes opens a new route to explore to increase understanding of the patholophysiology of the APS and to propose new alternatives and therapeutic targets.

Renal allograft thrombosis is the most frequent and devastating complication in the early postrenal transplantation period. Several risk factors to develop graft thrombosis depending on donors and recipients are well known. Antiphospholipid syndrome (APS) is well recognized as an important cause of kidney injury, with specific clinical and histological features that may lead to renal injury caused by thrombosis at any location within the renal vasculature. There are 3 forms of APS, primary (the most common form), associated to other systemic autoimmune diseases (SAD-APS), and catastrophic. Nevertheless, patients with SAD-APS and renal failure only represent 2% to 5% in hemodialysis or transplantation. The presence of pretransplant antiphospholipid antibodies increases risk of graft thrombosis. A new form of APS based on IgA anti-β-2-glycoprotein-I (B2GPI) antibodies, representing up to 30% of patients in end-stage renal disease and renal transplantation, is the main independent risk factor for graft thrombosis and early graft loss after renal transplantation. In addition, B2GP1 bound to IgA aB2GP1 immunocomplexes have been described as a marker to predict thrombosis after renal transplantation in patients with antiphospholipid antibodies. Anticoagulation remains the main treatment to prevent renal allograft thrombosis, although new preventive strategies are coming. Future studies may help to identify better therapeutic targets.

Background: Graft thrombosis is a devastating complication after renal transplantation. We recently described the association of anti-beta-2-glycoprotein-I (IgA-ab2GP1) antibodies with early graft loss mainly caused by thrombosis in a monocenter study., Methods: Multicenter prospective observational cohort study., Setting and Participants: Seven hundred forty patients from five hospitals of the Spanish Forum Renal Group transplanted from 2000 to 2002 were prospectively followed-up for 10 years., Outcomes: Early graft loss and graft loss by thrombosis., Measurements: The presence of IgA anti-B2GP1 antibodies in pretransplant serum was examined using the same methodology in all the patients., Results: At transplantation, 288 patients were positive for IgA-B2GP1 (39%, Group-1) and the remaining were negative (Group-2). Graft loss at 6 months was higher in Group-1 (12.5 vs. 4.2% p  < 0.001), vessel thrombosis being the most frequent cause of early graft loss, especially in Group-1 (6.9 vs. 0.4% p  < 0.001). IgA-aB2GP1 was the most important independent risk factor for graft thrombosis (hazard ratio: 13.83; 95% CI: 3.17-60.27, p  < 0.001). Furthermore, the, presence of IgA-aB2GP1 was associated with early graft loss and delayed graft function. At 10 years, survival figures were also lower in Group-1: graft survival was lower compared with Group-2 (60.4 vs. 76.8%, p  < 0.001). Mortality was significantly higher in Group-1 (19.8 vs. 12.2%, p  = 0.005)., Limitations: Patients were obtained during a 3-year period (1 January 2000-31 December 2002) and kidneys were only transplanted from brain-dead donors. Nowadays, the patients are older and the percentage of sensitized and retransplants is high., Conclusion: In a prospective observational multicenter study, we were able to corroborate that pretransplant presence of IgA-aB2GP1 was the main risk factor for graft thrombosis and early graft loss. Therefore, a prospective study is needed to evaluate the efficacy and safety of prophylactic anticoagulation to avoid this severe complication.

In the current immunosuppressive therapy era, vessel thrombosis is the most common cause of early graft loss after renal transplantation. The prevalence of IgA anti-β2-glycoprotein I antibodies (IgA-aB2GPI-ab) in patients on dialysis is elevated (>30%), and these antibodies correlate with mortality and cardiovascular morbidity. To evaluate the effect of IgA-aB2GPI-ab in patients with transplants, we followed all patients transplanted from 2000 to 2002 in the Hospital 12 de Octubre prospectively for 10 years. Presence of IgA-aB2GPI-ab in pretransplant serum was examined retrospectively. Of 269 patients, 89 patients were positive for IgA-aB2GPI-ab (33%; group 1), and the remaining patients were negative (67%; group 2). Graft loss at 6 months post-transplant was significantly higher in group 1 (10 of 89 versus 3 of 180 patients in group 2; P=0.002). The most frequent cause of graft loss was thrombosis of the vessels, which was observed only in group 1 (8 of 10 versus 0 of 3 patients in group 2; P=0.04). Multivariate analysis showed that the presence of IgA-aB2GPI-ab was an independent risk factor for early graft loss (P=0.04) and delayed graft function (P=0.04). There were no significant differences regarding patient survival between the two groups. Graft survival was similar in both groups after 6 months. In conclusion, patients with pretransplant IgA-aB2GPI-ab have a high risk of early graft loss caused by thrombosis and a high risk of delayed graft function. Therefore, pretransplant IgA-aB2GPI-ab may have a detrimental effect on early clinical outcomes after renal transplantation., (Copyright © 2015 by the American Society of Nephrology.)

In the follow-up of transplanted patients under immunosupression, the functional assessment of CD4+ T cells activation by measuring intracellular ATP levels in vitro, using the Immuknow test give information on how immune system is functioning. Therefore, it has been reported that low levels of ATP correlate with the risk of opportunistic infection. Although limited, comprehensive results in adult recipients as well as in pediatric transplanted patients have been reported. Forty stable liver pediatric transplanted patients (mean age: 11.0 years [SD 5.65]), within at least 1 year of transplant were selected for a scheduled review, and an unique determination of Immuknow was performed. Average ATP levels were 317 ng/mL (200-400 ng/mL) which were similar to the values observed in adult population. ATP values among patients with monotherapy Cyclosporin A (CSA) or tacrolimus (TAC) were significantly higher (P = .005) than in patients with double immunosupressive therapy using either CSA/TAC + Mycophenolate Mofetil (MMF). In CSA treatment, there are significant differences (P = .0003) between monotherapy and double therapy, but in the case of TAC we did not find differences (P > .1). A single determination of levels of ATP on CD4+ lymphocytes, can provide additional information that could be used as a complementary test to guide immunosuppressive therapy in paediatric liver transplant recipients., (Copyright © 2012 Elsevier Inc. All rights reserved.)