Impaired antigen-specific B-cell responses after Influenza vaccination in kidney transplant recipients receiving co-stimulation blockade with Belatacept

Inhibidores de la calcineurina; Vacunación antigripal; Trasplante de riñónCalcineurin inhibitors; Influenza vaccination; Kidney transplantationInhibidors de la calcineurina; Vacunació antigripal; Trasplantament de ronyóEmerging data suggest that costimulation blockade with belatacept effectively controls humoral alloimmune responses. However, whether this effect may be deleterious for protective anti-infectious immunity remains poorly understood. We performed a mechanistic exploratory study in 23 kidney transplant recipients receiving either the calcineurin-inhibitor tacrolimus (Tac, n=14) or belatacept (n=9) evaluating different cellular immune responses after influenza vaccination such as activated T follicular Helper (Tfh), plasmablasts and H1N1 hemagglutinin (HA)-specific memory B cells (HA+mBC) by flow-cytometry, and anti-influenza antibodies by hemagglutination inhibition test (HI), at baseline and days 10, 30 and 90 post-vaccination. The proportion of CD4+CD54RA-CXCR5+ Tfh was lower in belatacept than Tac patients at baseline (1.86%[1.25-3.03] vs 4.88%[2.40-8.27], p=0.01) and remained stable post-vaccination. At M3, HA+mBc were significantly higher in Tac-treated patients (0.56%[0.32-1.49] vs 0.27%[0.13-0.44], p=0.04) and correlated with activated Tfh numbers. When stratifying patients according to baseline HA+mBc frequencies, belatacept patients with low HA+mBC displayed significantly lower HA+mBc increases after vaccination than Tac patients (1.28[0.94-2.4] vs 2.54[1.73-5.70], p=0.04). Also, belatacept patients displayed significantly lower seroprotection rates against H1N1 at baseline than Tac-treated patients (44.4% vs 84.6%) as well as lower seroconversion rates at days 10, 30 and 90 after vaccination (50% vs 0%, 63.6% vs 0%, and 63.6% vs 0%, respectively). We show the efficacy of belatacept inhibiting T-dependent antigen-specific humoral immune responses, active immunization should be highly encouraged before starting belatacept therapy.This work was supported by the Instituto de Salud Carlos III (ISCIII) (grant numbers ICI14/00242 and PI16/01321, PI19/01710) and by the European Union’s Horizon 2020 Research and innovation program (grant agreement 754995). Also, this work was partly supported by the SLT002/16/00183 grant, from the Department of Health of the Generalitat de Catalunya by the call “Accioí instrumental de programes derecerca orientats en l’àmbit de la recerca i la innovacioí en salut.” The authors thank the Research Centers of Catalonia (CERCA) Programme/Generalitat de Catalunya for institutional support. OB was awarded with an intensification grant from the “Instituto de Salud Carlos III” [INT19/00051]

Donor/Recipient HLA Molecular Mismatch Scores Predict Primary Humoral and Cellular Alloimmunity in Kidney Transplantation

Donor/recipient molecular human leukocyte antigen (HLA) mismatch predicts primary B-cell alloimmune activation, yet the impact on de novo donor-specific T-cell alloimmunity (dnDST) remains undetermined. The hypothesis of our study is that donor/recipient HLA mismatches assessed at the molecular level may also influence a higher susceptibility to the development of posttransplant primary T-cell alloimmunity. In this prospective observational study, 169 consecutive kidney transplant recipients without preformed donor-specific antibodies (DSA) and with high resolution donor/recipient HLA typing were evaluated for HLA molecular mismatch scores using different informatic algorithms [amino acid mismatch, eplet MM, and Predicted Indirectly Recognizable HLA Epitopes (PIRCHE-II)]. Primary donor-specific alloimmune activation over the first 2 years posttransplantation was assessed by means of both dnDSA and dnDST using single antigen bead (SAB) and IFN-γ ELISPOT assays, respectively. Also, the predominant alloantigen presenting pathway priming DST alloimmunity and the contribution of main alloreactive T-cell subsets were further characterized in vitro. Pretransplantation, 78/169 (46%) were DST+ whereas 91/169 (54%) DST-. At 2 years, 54/169 (32%) patients showed detectable DST responses: 23/54 (42%) dnDST and 31/54 (57%) persistently positive (persistDST+). 24/169 (14%) patients developed dnDSA. A strong correlation was observed between the three distinct molecular mismatch scores and they all accurately predicted dnDSA formation, in particular at the DQ locus. Likewise, HLA molecular incompatibility predicted the advent of dnDST, especially when assessed by PIRCHE-II score (OR 1.014 95% CI 1.001-1.03, p=0.04). While pretransplant DST predicted the development of posttransplant BPAR (OR 5.18, 95% CI=1.64-16.34, p=0.005) and particularly T cell mediated rejection (OR 5.33, 95% CI=1.45-19.66, p=0.012), patients developing dnDST were at significantly higher risk of subsequent dnDSA formation (HR 2.64, 95% CI=1.08-6.45, p=0.03). In vitro experiments showed that unlike preformed DST that is predominantly primed by CD8+ direct pathway T cells, posttransplant DST may also be activated by the indirect pathway of alloantigen presentation, and predominantly driven by CD4+ alloreactive T cells in an important proportion of patients. De novo donor-specific cellular alloreactivity seems to precede subsequent humoral alloimmune activation and is influenced by a poor donor/recipient HLA molecular matching

Impaired antigen-specific B-cell responses after Influenza vaccination in kidney transplant recipients receiving co-stimulation blockade with Belatacept

Emerging data suggest that costimulation blockade with belatacept effectively controls humoral alloimmune responses. However, whether this effect may be deleterious for protective anti-infectious immunity remains poorly understood. We performed a mechanistic exploratory study in 23 kidney transplant recipients receiving either the calcineurin-inhibitor tacrolimus (Tac, n=14) or belatacept (n=9) evaluating different cellular immune responses after influenza vaccination such as activated T follicular Helper (Tfh), plasmablasts and H1N1 hemagglutinin (HA)-specific memory B cells (HA(+)mBC) by flow-cytometry, and anti-influenza antibodies by hemagglutination inhibition test (HI), at baseline and days 10, 30 and 90 post-vaccination. The proportion of CD4+CD54RA-CXCR5+ Tfh was lower in belatacept than Tac patients at baseline (1.86%[1.25-3.03] vs 4.88%[2.40-8.27], p=0.01) and remained stable post-vaccination. At M3, HA(+)mBc were significantly higher in Tac-treated patients (0.56%[0.32-1.49] vs 0.27%[0.13-0.44], p=0.04) and correlated with activated Tfh numbers. When stratifying patients according to baseline HA(+)mBc frequencies, belatacept patients with low HA(+)mBC displayed significantly lower HA(+)mBc increases after vaccination than Tac patients (1.28[0.94-2.4] vs 2.54[1.73-5.70], p=0.04). Also, belatacept patients displayed significantly lower seroprotection rates against H1N1 at baseline than Tac-treated patients (44.4% vs 84.6%) as well as lower seroconversion rates at days 10, 30 and 90 after vaccination (50% vs 0%, 63.6% vs 0%, and 63.6% vs 0%, respectively). We show the efficacy of belatacept inhibiting T-dependent antigen-specific humoral immune responses, active immunization should be highly encouraged before starting belatacept therapy

C5b9 Deposition in Glomerular Capillaries Is Associated With Poor Kidney Allograft Survival in Antibody-Mediated Rejection

C4d deposition in peritubular capillaries (PTC) reflects complement activation in antibody-mediated rejection (ABMR) of kidney allograft. However, its association with allograft survival is controversial. We hypothesized that capillary deposition of C5b9—indicative of complement-mediated injury—is a severity marker of ABMR. This pilot study aimed to determine the frequency, location and prognostic impact of these deposits in ABMR. We retrospectively selected patients diagnosed with ABMR in two French transplantation centers from January 2005 to December 2014 and performed C4d and C5b9 staining by immunohistochemistry. Fifty-four patients were included. Median follow-up was 52.5 (34.25–73.5) months. Thirteen patients (24%) had C5b9 deposits along glomerular capillaries (GC). Among these, seven (54%) had a global and diffuse staining pattern. Twelve of the C5b9+ patients also had deposition of C4d in GC and PTC. C4d deposits along GC and PTC were not associated with death-censored allograft survival (p = 0.42 and 0.69, respectively). However, death-censored allograft survival was significantly lower in patients with global and diffuse deposition of C5b9 in GC than those with a segmental pattern or no deposition (median survival after ABMR diagnosis, 6 months, 40.5 months and 44 months, respectively; p = 0.015). Double contour of glomerular basement membrane was diagnosed earlier after transplantation in C5b9+ ABMR than in C5b9– ABMR (median time after transplantation, 28 vs. 85 months; p = 0.058). In conclusion, we identified a new pattern of C5b9+ ABMR, associated with early onset of glomerular basement membrane duplication and poor allograft survival. Complement inhibitors might be a therapeutic option for this subgroup of patients

Race-free estimated glomerular filtration rate equation in kidney transplant recipients:development and validation study

OBJECTIVE: To compare the performance of a newly developed race-free kidney recipient specific glomerular filtration rate (GFR) equation with the three current main equations for measuring GFR in kidney transplant recipients.DESIGN: Development and validation study SETTING: 17 cohorts in Europe, the United States, and Australia (14 transplant centres, three clinical trials).PARTICIPANTS: 15 489 adults (3622 in development cohort (Necker, Saint Louis, and Toulouse hospitals, France), 11 867 in multiple external validation cohorts) who received kidney transplants between 1 January 2000 and 1 January 2021.MAIN OUTCOME MEASURE: The main outcome measure was GFR, measured according to local practice. Performance of the GFR equations was assessed using P 30 (proportion of estimated GFR (eGFR) within 30% of measured GFR (mGFR)) and correct classification (agreement between eGFR and mGFR according to GFR stages). The race-free equation, based on creatinine level, age, and sex, was developed using additive and multiplicative linear regressions, and its performance was compared with the three current main GFR equations: Modification of Diet in Renal Disease (MDRD) equation, Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) 2009 equation, and race-free CKD-EPI 2021 equation. RESULTS: The study included 15 489 participants, with 50 464 mGFR and eGFR values. The mean GFR was 53.18 mL/min/1.73m 2 (SD 17.23) in the development cohort and 55.90 mL/min/1.73m 2 (19.69) in the external validation cohorts. Among the current GFR equations, the race-free CKD-EPI 2021 equation showed the lowest performance compared with the MDRD and CKD-EPI 2009 equations. When race was included in the kidney recipient specific GFR equation, performance did not increase. The race-free kidney recipient specific GFR equation showed significantly improved performance compared with the race-free CKD-EPI 2021 equation and performed well in the external validation cohorts (P 30 ranging from 73.0% to 91.3%). The race-free kidney recipient specific GFR equation performed well in several subpopulations of kidney transplant recipients stratified by race (P 30 73.0-91.3%), sex (72.7-91.4%), age (70.3-92.0%), body mass index (64.5-100%), donor type (58.5-92.9%), donor age (68.3-94.3%), treatment (78.5-85.2%), creatinine level (72.8-91.3%), GFR measurement method (73.0-91.3%), and timing of GFR measurement post-transplant (72.9-95.5%). An online application was developed that estimates GFR based on recipient's creatinine level, age, and sex (https://transplant-prediction-system.shinyapps.io/eGFR_equation_KTX/). CONCLUSION: A new race-free kidney recipient specific GFR equation was developed and validated using multiple, large, international cohorts of kidney transplant recipients. The equation showed high accuracy and outperformed the race-free CKD-EPI 2021 equation that was developed in individuals with native kidneys.TRIAL REGISTRATION: ClinicalTrials.gov NCT05229939.</p

The anterolateral ligament of the knee: unwrapping the enigma. Anatomical study and comparison to previous reports.

It has been suggested that the anterolateral ligament (ALL) of the knee may have importance in limiting rotational instability, and reconstruction may prevent a continued pivot-shift following anterior cruciate ligament surgery. However, the anatomy of this ligament has not been consistently reported in recent publications. We describe our experience of cadaveric dissection with reference to other published work.This article is freely available via Open Access. Click on the 'Additional Link' above to access the full-text from the publisher's site.Published (Open Access

The anterolateral complex of the knee: results from the International ALC Consensus Group Meeting

The structure and function of the anterolateral complex (ALC) of the knee has created much controversy since the 're-discovery' of the anterolateral ligament (ALL) and its proposed role in aiding control of anterolateral rotatory laxity in the anterior cruciate ligament (ACL) injured knee. A group of surgeons and researchers prominent in the field gathered to produce consensus as to the anatomy and biomechanical properties of the ALC. The evidence for and against utilisation of ALC reconstruction was also discussed, generating a number of consensus statements by following a modified Delphi process. Key points include that the ALC consists of the superficial and deep aspects of the iliotibial tract with its Kaplan fibre attachments on the distal femur, along with the ALL, a capsular structure within the anterolateral capsule. A number of structures attach to the area of the Segond fracture including the capsule-osseous layer of the iliotibial band, the ALL and the anterior arm of the short head of biceps, and hence it is not clear which is responsible for this lesion. The ALC functions to provide anterolateral rotatory stability as a secondary stabiliser to the ACL. Whilst biomechanical studies have shown that these structures play an important role in controlling stability at the time of ACL reconstruction, the optimal surgical procedure has not yet been defined clinically. Concern remains that these procedures may cause constraint of motion, yet no clinical studies have demonstrated an increased risk of osteoarthritis development. Furthermore, clinical evidence is currently lacking to support clear indications for lateral extra-articular procedures as an augmentation to ACL reconstruction. The resulting statements and scientific rationale aim to inform readers on the most current thinking and identify areas of needed basic science and clinical research to help improve patient outcomes following ACL injury and subsequent reconstruction. Level of evidence V

Les anticorps anti-HLA au cours du rejet à médiation humorale : rôle de la sous-classe et de la glycosylation des anticorps

Antibody-mediated rejection (ABMR) is now recognized as the leading cause of graft loss beyond the first year. De novo donor-specific anti-HLA antibodies (DSAdn) are the main risk factor for ABMR after kidney transplantation. However, the clinical course after the detection of a DSAdn is extremely heterogeneous, suggesting that not all DSA have the same pathogenicity. Several characteristics of DSAdn have been identified as being associated with a higher risk of ABMR or graft loss such as the “strength” of the antibodies (evaluated by the MFI in the Luminex Single Beads Antigen test), their ability to activate the classical complement pathway and the detection of IgG3 subclass. In this work, we studied the role of the DSA subclasses distribution and the DSA glycosylation profile in ABMR occurrence and graft outcomes. For this, we developed an innovative method for DSA characterization based on mass-spectrometry.In the first part of this work, we highlighted that the DSAs were always composed of the four IgG subclasses but with a variable distribution. The distribution of subclasses was specific to DSA with more IgG1, more IgG3, more IgG4 but less IgG2 compared to total IgG. A high proportion of IgG3 (> 6.4%) was significantly associated with ABMR occurrence and with ABMR severity (more complement deposition and more microvascular inflammation) and with the decline of the glomerular filtration rate, independently to other DSA characteristics, in particular the MFI value.In the second part of this work, we showed for the first time an association between the glycosylation profile of DSA and the risk of ABMR. DSA from ABMR+ patients exhibited a pro-inflammatory glycosylation profile, associating a lower galactosylation of IgG1, a lower sialylation of IgG3 and a higher proportion of bisecting GlcNAc. Hyposialylation of IgG3 appears to be a promising factor in the ABMR risk prediction. These results also potentially pave the way to new therapeutic strategies which are particularly expected, the effectiveness of current therapies often being disappointing.Le rejet à médiation humorale (ABMR) est aujourd’hui reconnu comme la première cause de perte du greffon rénal au-delà de la première année. Les anticorps anti-HLA spécifiques du donneur de novo (DSAdn) sont le facteur de risque principal d’ABMR après transplantation rénale. Ils sont au centre des mécanismes physiopathologiques impliqués au cours de cette pathologie. Cependant, l’évolution clinique après la détection d’un DSAdn est extrêmement hétérogène suggérant que tous n’ont pas la même pathogénicité. Plusieurs caractéristiques des DSAdn ont été identifiées comme étant associées à un risque plus élevé d’ABMR ou de perte du greffon comme la « force » des anticorps (évaluée par la MFI au test Luminex Single Antigen), leur capacité à fixer et activer la voie classique du complément et la détection d’une sous-classe IgG3. Dans ce travail de thèse, j’ai étudié le rôle de la répartition des différentes sous-classe IgG et du profil de glycosylation des DSA au cours de l’ABMR, grâce à la mise au point d’une technique innovante basée sur la spectrométrie de masse.Dans la première partie de ce travail, nous avons mis en évidence que les DSA étaient toujours composés des quatre sous-classes d’IgG mais avec une répartition variable selon les patients. La distribution des sous-classes des DSA était différente de celle des IgG totales avec plus d’IgG1, plus d’IgG3, plus d’IgG4 mais moins d’IgG2. Une proportion élevée d’IgG3 (>6.4%) était significativement associée à la présence d’un ABMR, à la sévérité histologique de l’ABMR avec plus de dépôts de complément et plus d’inflammation de la microcirculation (glomérulite et capillarite péri-tubulaire) et au déclin du débit de filtration glomérulaire, indépendamment des autres caractéristiques du DSA, en particulier de la valeur de MFI.Dans la deuxième partie de ce travail, nous avons montré pour la première fois une association entre le profil de glycosylation des DSA et le risque d’ABMR. Le groupe de patients présentant un ABMR avaient des DSA dont les sous-classes IgG1 et IgG3 exhibaient un profil de glycosylation pro-inflammatoire associant une plus faible galactosylation des IgG1, une plus faible sialylation des IgG3 et une proportion plus élevée de GlcNAc en position bissectrice. L’hyposialylation des IgG3 semble un facteur prometteur pour prédire du risque d’ABMR. Ces résultats ouvrent aussi potentiellement la voie à de nouvelles stratégies thérapeutiques qui sont particulièrement attendues, l’efficacité des thérapeutiques utilisées actuellement étant souvent décevante

Anti-HLA antibodies in antibody-mediated rejection : role of IgG subclasses distribution and glycosylation

Le rejet à médiation humorale (ABMR) est aujourd’hui reconnu comme la première cause de perte du greffon rénal au-delà de la première année. Les anticorps anti-HLA spécifiques du donneur de novo (DSAdn) sont le facteur de risque principal d’ABMR après transplantation rénale. Ils sont au centre des mécanismes physiopathologiques impliqués au cours de cette pathologie. Cependant, l’évolution clinique après la détection d’un DSAdn est extrêmement hétérogène suggérant que tous n’ont pas la même pathogénicité. Plusieurs caractéristiques des DSAdn ont été identifiées comme étant associées à un risque plus élevé d’ABMR ou de perte du greffon comme la « force » des anticorps (évaluée par la MFI au test Luminex Single Antigen), leur capacité à fixer et activer la voie classique du complément et la détection d’une sous-classe IgG3. Dans ce travail de thèse, j’ai étudié le rôle de la répartition des différentes sous-classe IgG et du profil de glycosylation des DSA au cours de l’ABMR, grâce à la mise au point d’une technique innovante basée sur la spectrométrie de masse.Dans la première partie de ce travail, nous avons mis en évidence que les DSA étaient toujours composés des quatre sous-classes d’IgG mais avec une répartition variable selon les patients. La distribution des sous-classes des DSA était différente de celle des IgG totales avec plus d’IgG1, plus d’IgG3, plus d’IgG4 mais moins d’IgG2. Une proportion élevée d’IgG3 (>6.4%) était significativement associée à la présence d’un ABMR, à la sévérité histologique de l’ABMR avec plus de dépôts de complément et plus d’inflammation de la microcirculation (glomérulite et capillarite péri-tubulaire) et au déclin du débit de filtration glomérulaire, indépendamment des autres caractéristiques du DSA, en particulier de la valeur de MFI.Dans la deuxième partie de ce travail, nous avons montré pour la première fois une association entre le profil de glycosylation des DSA et le risque d’ABMR. Le groupe de patients présentant un ABMR avaient des DSA dont les sous-classes IgG1 et IgG3 exhibaient un profil de glycosylation pro-inflammatoire associant une plus faible galactosylation des IgG1, une plus faible sialylation des IgG3 et une proportion plus élevée de GlcNAc en position bissectrice. L’hyposialylation des IgG3 semble un facteur prometteur pour prédire du risque d’ABMR. Ces résultats ouvrent aussi potentiellement la voie à de nouvelles stratégies thérapeutiques qui sont particulièrement attendues, l’efficacité des thérapeutiques utilisées actuellement étant souvent décevante.Antibody-mediated rejection (ABMR) is now recognized as the leading cause of graft loss beyond the first year. De novo donor-specific anti-HLA antibodies (DSAdn) are the main risk factor for ABMR after kidney transplantation. However, the clinical course after the detection of a DSAdn is extremely heterogeneous, suggesting that not all DSA have the same pathogenicity. Several characteristics of DSAdn have been identified as being associated with a higher risk of ABMR or graft loss such as the “strength” of the antibodies (evaluated by the MFI in the Luminex Single Beads Antigen test), their ability to activate the classical complement pathway and the detection of IgG3 subclass. In this work, we studied the role of the DSA subclasses distribution and the DSA glycosylation profile in ABMR occurrence and graft outcomes. For this, we developed an innovative method for DSA characterization based on mass-spectrometry.In the first part of this work, we highlighted that the DSAs were always composed of the four IgG subclasses but with a variable distribution. The distribution of subclasses was specific to DSA with more IgG1, more IgG3, more IgG4 but less IgG2 compared to total IgG. A high proportion of IgG3 (> 6.4%) was significantly associated with ABMR occurrence and with ABMR severity (more complement deposition and more microvascular inflammation) and with the decline of the glomerular filtration rate, independently to other DSA characteristics, in particular the MFI value.In the second part of this work, we showed for the first time an association between the glycosylation profile of DSA and the risk of ABMR. DSA from ABMR+ patients exhibited a pro-inflammatory glycosylation profile, associating a lower galactosylation of IgG1, a lower sialylation of IgG3 and a higher proportion of bisecting GlcNAc. Hyposialylation of IgG3 appears to be a promising factor in the ABMR risk prediction. These results also potentially pave the way to new therapeutic strategies which are particularly expected, the effectiveness of current therapies often being disappointing

Les anticorps anti-HLA au cours du rejet à médiation humorale : rôle de la sous-classe et de la glycosylation des anticorps

Antibody-mediated rejection (ABMR) is now recognized as the leading cause of graft loss beyond the first year. De novo donor-specific anti-HLA antibodies (DSAdn) are the main risk factor for ABMR after kidney transplantation. However, the clinical course after the detection of a DSAdn is extremely heterogeneous, suggesting that not all DSA have the same pathogenicity. Several characteristics of DSAdn have been identified as being associated with a higher risk of ABMR or graft loss such as the “strength” of the antibodies (evaluated by the MFI in the Luminex Single Beads Antigen test), their ability to activate the classical complement pathway and the detection of IgG3 subclass. In this work, we studied the role of the DSA subclasses distribution and the DSA glycosylation profile in ABMR occurrence and graft outcomes. For this, we developed an innovative method for DSA characterization based on mass-spectrometry.In the first part of this work, we highlighted that the DSAs were always composed of the four IgG subclasses but with a variable distribution. The distribution of subclasses was specific to DSA with more IgG1, more IgG3, more IgG4 but less IgG2 compared to total IgG. A high proportion of IgG3 (> 6.4%) was significantly associated with ABMR occurrence and with ABMR severity (more complement deposition and more microvascular inflammation) and with the decline of the glomerular filtration rate, independently to other DSA characteristics, in particular the MFI value.In the second part of this work, we showed for the first time an association between the glycosylation profile of DSA and the risk of ABMR. DSA from ABMR+ patients exhibited a pro-inflammatory glycosylation profile, associating a lower galactosylation of IgG1, a lower sialylation of IgG3 and a higher proportion of bisecting GlcNAc. Hyposialylation of IgG3 appears to be a promising factor in the ABMR risk prediction. These results also potentially pave the way to new therapeutic strategies which are particularly expected, the effectiveness of current therapies often being disappointing.Le rejet à médiation humorale (ABMR) est aujourd’hui reconnu comme la première cause de perte du greffon rénal au-delà de la première année. Les anticorps anti-HLA spécifiques du donneur de novo (DSAdn) sont le facteur de risque principal d’ABMR après transplantation rénale. Ils sont au centre des mécanismes physiopathologiques impliqués au cours de cette pathologie. Cependant, l’évolution clinique après la détection d’un DSAdn est extrêmement hétérogène suggérant que tous n’ont pas la même pathogénicité. Plusieurs caractéristiques des DSAdn ont été identifiées comme étant associées à un risque plus élevé d’ABMR ou de perte du greffon comme la « force » des anticorps (évaluée par la MFI au test Luminex Single Antigen), leur capacité à fixer et activer la voie classique du complément et la détection d’une sous-classe IgG3. Dans ce travail de thèse, j’ai étudié le rôle de la répartition des différentes sous-classe IgG et du profil de glycosylation des DSA au cours de l’ABMR, grâce à la mise au point d’une technique innovante basée sur la spectrométrie de masse.Dans la première partie de ce travail, nous avons mis en évidence que les DSA étaient toujours composés des quatre sous-classes d’IgG mais avec une répartition variable selon les patients. La distribution des sous-classes des DSA était différente de celle des IgG totales avec plus d’IgG1, plus d’IgG3, plus d’IgG4 mais moins d’IgG2. Une proportion élevée d’IgG3 (>6.4%) était significativement associée à la présence d’un ABMR, à la sévérité histologique de l’ABMR avec plus de dépôts de complément et plus d’inflammation de la microcirculation (glomérulite et capillarite péri-tubulaire) et au déclin du débit de filtration glomérulaire, indépendamment des autres caractéristiques du DSA, en particulier de la valeur de MFI.Dans la deuxième partie de ce travail, nous avons montré pour la première fois une association entre le profil de glycosylation des DSA et le risque d’ABMR. Le groupe de patients présentant un ABMR avaient des DSA dont les sous-classes IgG1 et IgG3 exhibaient un profil de glycosylation pro-inflammatoire associant une plus faible galactosylation des IgG1, une plus faible sialylation des IgG3 et une proportion plus élevée de GlcNAc en position bissectrice. L’hyposialylation des IgG3 semble un facteur prometteur pour prédire du risque d’ABMR. Ces résultats ouvrent aussi potentiellement la voie à de nouvelles stratégies thérapeutiques qui sont particulièrement attendues, l’efficacité des thérapeutiques utilisées actuellement étant souvent décevante