Donor-specific Antibody Formation Research Articles

225.8: Polymorphisms in molecules regulating follicular helper T cell differentiation predict de novo donor specific antibody formation after liver transplantation.

225.8: Polymorphisms in molecules regulating follicular helper T cell differentiation predict de novo donor specific antibody formation after liver transplantation.

Effect of angiotensin II type 1 receptor antibodies on graft function and survival in paediatric kidney transplant recipients.

HLA donor specific antibodies (DSA) are implicated in antibody-mediated rejection (AMR), graft dysfunction and failure in kidney transplant (KT) recipients. Non-HLA antibodies including angiotensin II type 1 receptor (AT1R) may also play a role in AMR, impact graft function and survival. Data is limited in paediatric KT cohorts. We aimed to assess the prevalence and effect of pre-transplant AT1R antibodies on rejection, graft function and survival in paediatric KT recipients. This was a retrospective cohort study conducted across two paediatric centres including KT recipients with a pre-transplant AT1R antibody level. Outcomes included rejection, de novo DSA formation, graft function, failure, proteinuria and hypertension. Of 71 individuals, 72% recorded a positive pre-transplant AT1R Ab level (≥17 U/mL). Over a median follow-up of 4.7 years, AT1R Ab positivity demonstrated a trend towards increased risk of rejection however was not statistically significant (HR 3.45, 95% CI 0.97-12.35, p-value 0.06). Sensitivity analysis with AT1R Ab levels of ≥25 U/mL (HR 2.05 95% CI 0.78-5.39, p-value 0.14) and ≥40 U/mL (HR 1.32, CI 95% 0.55-3.17, p-value 0.53) validated this. De novo DSA formation occurred more frequently with AT1R Ab positivity (41% vs. 20%, p-value 0.9). AT1R Ab was not associated with hypertension, proteinuria, graft failure or dysfunction. In conclusion, this cohort study demonstrated a high prevalence of pre-transplant AT1R Ab positivity (72%). AT1R Ab positivity demonstrated a trend towards increased risk of rejection and de novo DSA formation however did not meet statistical significance. There was no association between AT1R Ab and hypertension, proteinuria, graft failure or dysfunction.

Activation and Regulation of Indirect Alloresponses in Transplanted Patients With Donor Specific Antibodies and Chronic Rejection.

Following transplantation, human CD4+T cells can respond to alloantigen using three distinct pathways. Direct and semi-direct responses are considered potent, but brief, so contribute mostly to acute rejection. Indirect responses are persistent and prolonged, involve B cells as critical antigen presenting cells, and are an absolute requirement for development of donor specific antibody, so more often mediate chronic rejection. Novel in vitro techniques have furthered our understanding by mimicking in vivo germinal centre processes, including B cell antigen presentation to CD4+ T cells and effector cytokine responses following challenge with donor specific peptides. In this review we outline recent data detailing the contribution of CD4+ T follicular helper cells and antigen presenting B cells to donor specific antibody formation and antibody mediated rejection. Furthermore, multi-parametric flow cytometry analyses have revealed specific endogenous regulatory T and B subsets each capable of suppressing distinct aspects of the indirect response, including CD4+ T cell cytokine production, B cell maturation into plasmablasts and antibody production, and germinal centre maturation. These data underpin novel opportunities to control these aberrant processes either by targeting molecules critical to indirect alloresponses or potentiating suppression via exogenous regulatory cell therapy.

Long-Term Outcome after Early Mammalian Target of Rapamycin Inhibitor-Based Immunosuppression in Kidney Transplant Recipients.

Background: The use of mammalian target of rapamycin inhibitors (mTORis) in kidney transplantation increases the risk of donor-specific human leukocyte antigen (HLA) antibody formation and rejection. Here, we investigated the long-term consequences of early mTORi treatment compared to calcineurin inhibitor (CNI) treatment. Methods: In this retrospective single-center analysis, key outcome parameters were compared between patients participating in randomized controlled immunosuppression trials between 1998 and 2011, with complete follow-up until 2018. The outcomes of eligible patients on a CNI-based regimen (n = 384) were compared with those of patients randomized to a CNI-free mTORi-based regimen (n = 81) and 76 patients randomized to a combination of CNI and mTORi treatments. All data were analyzed according to the intention-to-treat (ITT) principle. Results: Deviation from randomized immunosuppression for clinical reasons occurred significantly more often and much earlier in both mTORi-containing regimens than in the CNI treatment. Overall patient survival, graft survival, and death-censored graft survival did not differ between the treatment groups. Donor-specific HLA antibody formation and BPARs were significantly more common in both mTORi regimens than in the CNI-based immunosuppression. Conclusions: The tolerability and efficacy of the mTORi treatment in kidney graft recipients are inferior to those of CNI-based immunosuppression, while the long-term patient and graft survival rates were similar.

Association of HLA B- and T-cell molecular mismatches with HLA antibodies, rejection, and graft survival in pediatric kidney transplantation.

Optimizing graft survival and diminishing human leukocyte antigen (HLA) sensitization are essential for pediatric kidney transplant recipients. More precise HLA matching predicting epitope mismatches could reduce alloreactivity. We investigated the association of predicted HLA B- and T-cell molecular mismatches with the formation of de novo donor-specific antibodies, HLA antibodies, rejection, and graft survival. Forty-nine pediatric kidney transplant recipients transplanted from 2009 to 2020 were retrospectively studied. Donors and recipients were high-resolution HLA typed, and recipients were screened for HLA antibodies posttransplant. HLA-EMMA (HLA Epitope MisMatch Algorithm) and PIRCHE-II (Predicted Indirectly ReCognizable HLA Epitopes) predicted the molecular mismatches. The association of molecular mismatches and the end-points was explored with logistic regression. Five recipients (11%) developed de novo donor-specific antibodies. All five had de novo donor-specific antibodies against HLA class II, with four having HLA-DQ antibodies. We found no associations between PIRCHE-II or HLA-EMMA with de novo donor-specific antibodies, HLA sensitization, graft loss, or rejection. However, we did see a tendency towards an increased odds ratio in PIRCHE-II predicting de novo donor-specific antibodies formation, with an odds ratio of 1.12 (95% CI: 0.99; 1.28) on HLA class II. While the study revealed no significant associations between the number of molecular mismatches and outcomes, a notable trend was observed - indicating a reduced risk of dnDSA formation with improved molecular match. It is important to acknowledge, however, that the modest population size and limited observed outcomes preclude us from making definitive conclusions.

Marginal Zone B Cells Are Necessary for the Formation of Anti-donor IgG After Allogeneic Sensitization.

The formation of anti-major histocompatibility complex (MHC) antibodies is a significant barrier for many patients awaiting organ transplantation. Patients with preformed anti-MHC antibodies have limited options for suitable donors, and the formation of donor-specific anti-MHC antibodies after transplantation is a harbinger of graft rejection. Despite the recognized importance of anti-MHC antibodies, the mechanisms responsible for the differentiation of B cells after exposure to allogeneic antigens are poorly understood. To evaluate the differentiation of B cells in response to allogeneic antigen, we used a model of H-2 b C57Bl/6 sensitization with H-2 d antigen. We used a class I MHC tetramer-based approach to identify allogeneic B cells and flow cytometric crossmatch to identify allogeneic IgM and IgG. We found that although the formation of anti-H-2 d IgG was robust, few class-switched B cells and germinal center B cells were formed. Antigen-specific B cells did not express classical memory B-cell markers after sensitization but had an IgM + CD21 + marginal zone B-cell phenotype. The frequency of marginal zone B cells increased after sensitization. Depletion of marginal zone B cells before sensitization or skin grafting resulted in a significant diminution of anti-H-2 d IgG and fewer germinal center B cells. Adoptive transfer experiments revealed that marginal zone B cells more efficiently differentiated into germinal center B cells and anti-donor IgG-producing cells than follicular B cells. These results demonstrate an important role for marginal zone B cells as a reservoir of alloreactive B cells that are activated by allogeneic antigens.

Impact of HLA Eplet Mismatch on De Novo Donor Specific Antibody Formation After Kidney Transplantation

HLA eplet mismatching is an alternative approach to assess the risk of developing de novo donor-specific antibodies (dnDSA) in kidney transplantation. This strategy may offer more precise risk stratification than conventional approaches. This study aimed to find the association between HLA eplet mismatches and dnDSA formation in Thai kidney transplant recipients. A retrospective cohort study of kidney transplant recipients transplanted between 2000 and 2021 at Ramathibodi Hospital was performed. Recipients with pretransplant panel reactive antibody >0% or without DSA testing post-transplant were excluded. One hundred fifty recipients were included in the final study. High-resolution HLA typing was imputed by the HaploStat application. HLA eplet mismatch analysis was conducted using HLAMatchmaker. The association between the number of eplet mismatches and the risk of dnDSA formation was assessed by Cox regression analysis. Of 150 recipients, 43 were dnDSA-positive, and 107 were dnDSA-negative patients. Compared with the dnDSA-negative group, patients with class II dnDSA had significantly more HLA-DR/DQ antibody (Ab)-verified eplet mismatches (6 [IQR 4-8] vs 4 [IQR 1-7], P = .045). The receiver operating characteristics analysis showed that the HLA-DQ Ab-verified eplet mismatches ≥2 were the best predictive of HLA class II dnDSA development. The number of HLA-DQ Ab-verified eplet mismatches ≥2 had the highest hazard rate of HLA class II dnDSA occurrence (adjusted HR, 3.74; 95%CI, 1.24-11.24, P = .019). HLA-DQ Ab-verified eplet mismatches are significantly associated with class II dnDSA development. Our data supports the utility of HLA eplet mismatching for donor-recipient risk assessment.

Trajectories of postoperative serum troponin concentrations following pediatric heart transplantation

IntroductionTroponin is a readily measured serum biomarker of myocardial injury and death, but has not been well studied after pediatric heart transplants. The objective of this analysis is to describe the distribution and clinical determinants of serum troponin measured in the first week after pediatric heart transplantation. MethodsWe included all patients who underwent heart transplantation at Seattle Children’s Hospital between January 1, 2012 and December 31, 2016. During this period, serum Troponin-I (TnI) was measured daily in the first week after heart transplant. We described the distribution of serum TnT collected in this period. We examined the relationship between peak TnI with known pre- peri-operative risk factors for myocardial injury including etiology of heart failure, ischemia time, and donor to recipient characteristics. Logistic regression models were used to test the association between peak TnI with incidence of death or rejection and formation of donor specific antibodies within 1 year. Adjusted models included age, HF etiology, crossmatch status, and panel reactive antibodies. ResultsDuring the study period, 86 transplants were performed on 83 unique individuals. Serum TnI peaked at a median of 0.9 days after transplantation. In adjusted models, higher peak TnI was associated with death and/or rejection within 1-year post-transplant (Odds Ratio [95% confidence interval]: 1.10 [1.02, 1.19]). Higher peak TnI was not associated with de-novo DSA formation in adjusted models (OR [95%CI]: 1.01 [0.94, 1.09]). Post-transplant length of stay in the intensive care unit was positively correlated with peak TnI (r=0.36, p<0.001). ConclusionsThis study provides a description of serum TnI in the first week after pediatric heart transplant; a population for whom existing data is sparse. Post-transplant TnI reflects pre- and peri-operative factors such as ischemia time. This suggests TnI may have utility as a readily measurable biomarker of transplant-related myocardial injury. Our results serve as a basis to test the prognostic significance of higher post-transplant TnI in future studies.

Early progression of chronic histologic lesions in kidney transplant biopsies is not associated with HLA histocompatibility.

Early progression of chronic histologic lesions in kidney allografts represents the main finding in graft attrition. The objective of this retrospective cohort study was to elucidate whether HLA histocompatibility is associated with progression of chronic histologic lesions in the first year post-transplant. Established associations of de novo donor-specific antibody (dnDSA) formation with HLA mismatch and microvascular inflammation (MVI) were calculated to allow for comparability with other study cohorts. We included 117 adult kidney transplant recipients, transplanted between 2016 and 2020 from predominantly deceased donors, who had surveillance biopsies at 3 and 12 months. Histologic lesion scores were assessed according to the Banff classification. HLA mismatch scores [i.e. eplet, predicted indirectly recognizable HLA-epitopes algorithm (PIRCHE-II), HLA epitope mismatch algorithm (HLA-EMMA), HLA whole antigen A/B/DR] were calculated for all transplant pairs. Formation of dnDSAs was quantified by single antigen beads. More than one-third of patients exhibited a progression of chronic lesion scores by at least one Banff grade in tubular atrophy (ct), interstitial fibrosis (ci), arteriolar hyalinosis (ah) and inflammation in the area of interstitial fibrosis and tubular atrophy (i-IFTA) from the 3- to the 12-month biopsy. Multivariable proportional odds logistic regression models revealed no association of HLA mismatch scores with progression of histologic lesions, except for ah and especially HLA-EMMA DRB1 [odds ratio (OR)=1.10, 95% confidence interval (CI) 1.03-1.18]. Furthermore, the established associations of dnDSA formation with HLA mismatch and MVI (OR=5.31, 95% CI 1.19-22.57) could be confirmed in our cohort. These data support the association of HLA mismatch and alloimmune response, while suggesting that other factors contribute to early progression of chronic histologic lesions.

Comparative analysis of Basiliximab and Alemtuzumab induction therapies in blood type A2-to-B kidney transplantation: Impact on kidney function and de novo donor-specific HLA antibodies

PurposeBlood group B kidney transplant candidates have lower transplantation rates and longer waiting times compared to other blood groups. Kidney transplantation from blood group A2-to-B has offered a solution for these patients. This study aimed to investigate the impact of Basiliximab and Alemtuzumab induction therapies on kidney function and de novo donor-specific antibodies (DSA) in blood type A2-to-B kidney transplant recipients within the first 12 months of post-transplant. MethodsA retrospective analysis was conducted on 110 consecutive A2-to-B kidney transplant recipients between January 2015 and December 2022. Of these, 46 (41.8%) received Basiliximab, while 64 (58.2%) received Alemtuzumab as induction therapy. Demographics and comorbidities data were collected and compared between the two groups. Serum samples collected at 4- and 12-month intervals post-transplant were used to assess the presence of de novo DSA. Kidney allograft function was evaluated by monitoring serum creatinine levels and assessing Creatinine Clearance based on 24-h urine collection at various time points. ResultsDuring the follow-up period, 20.00% of patients who received Alemtuzumab developed de novo DSA, whereas none of the patients induced with Basiliximab developed de novo DSA (p = 0.038). Recipients who received Basiliximab were older (mean age = 72.00) and received higher Kidney Donor Profile Index (KDPI) kidneys (mean = 75) compared to those induced with Alemtuzumab (mean age = 58.00, mean KDPI = 49) (p < 0.001), with no significant difference observed in the last follow-up creatinine clearance or creatinine levels between the two groups (p = 0.28). ConclusionThe use of Basiliximab as induction immunosuppression in A2-to-B kidney transplant recipients is associated with a lower incidence of de novo HLA DSA formation without significant differences in overall renal function compared to Alemtuzumab.

Belatacept with time-limited tacrolimus coimmunosuppression modifies the 3-year risk of eplet mismatch in kidney transplantation

Solid organ transplant donor-recipient eplet mismatch has been correlated with donor-specific antibody (DSA) formation, antibody-mediated rejection, and overall rejection rates. However, studies have been predominantly in patients on tacrolimus-based immunosuppression regimens and have not fully explored differences in ethnically and racially diverse populations. Evidence indicates that patients on belatacept have lower rates of DSA formation, suggesting mediation of the immunogenicity of mismatched human leukocyte antigen polymorphisms. We performed a retrospective, single-center analysis of class II eplet disparity in a cohort of kidney transplant recipients treated using belatacept with tacrolimus induction (Bela/TacTL) or tacrolimus regimens between 2016 and 2019. Bela/TacTL (n = 294) and tacrolimus (n = 294) cohorts were propensity score-matched with standardized difference <0.15. Single-molecule eplet risk level was associated with immune event rates for both groups. In Cox regression analysis stratified by eplet risk level, Bela/TacTL immunosuppression was associated with a decreased rate of DSA (hazard ratio [HR] = 0.4), antibody-mediated rejection (HR = 0.2), and rejection (HR = 0.45). In the low-risk group, cumulative graft failure was lower for patients on Bela/TacTL (P < .02). Analysis of eplet mismatch burden may be a useful adjunct in identifying high-risk populations with increased immunosuppression requirements and should encourage the design of allocation rules to incentivize lower-risk pairings without negatively impacting equity in access.

P121 Correlation of HLA epitope mismatches with de novo donor-specific antibody formation in renal transplant recipients – A comparison of snowflake to HLAMatchmaker and PIRCHE scores

P121 Correlation of HLA epitope mismatches with de novo donor-specific antibody formation in renal transplant recipients – A comparison of snowflake to HLAMatchmaker and PIRCHE scores

Analysis of null deletion polymorphism of glutathione S-transferase theta (GSTT-1), associated with anti-GSTT-1 antibodies development in transplantation.

Glutathione S-transferase theta 1 (GSTT1) is an enzyme involved in phase II biotransformation processes and a member of a multigene family of detoxifying and clearing reactive oxygen species. GSTT1 is polymorphic like other biotransforming enzymes, allowing variability in hepatic conjugation processes. Immunological recognition of the GSTT1 alloantigen, as evidenced by donor-specific antibodies formation, has previously been observed in recipients lacking GSTT1 protein (called GSTT1-, GSTT*0, null phenotype or homozygous for the GSTT1 deletion) who receive liver or kidney transplants from GSTT1+ donors and is a risk factor for the development of de novo hepatitis following liver transplants from a GSTT1 expressing donor. Antibodies against GSTT1 are demonstrated in patients who are GSTT1 null and received a transplant from a GSTT1+ donor. Understanding the local population frequency of the GSTT1 deletion is of value in understanding the potential clinical risk of developing post-transplant complications, which can be attributed to the nonexpression of GSTT1. A population of 173 healthy donors of the Murcia Region in Southeast Spain was evaluated for a null allele of GSTT1 (n=173). DNA was extracted, and GSTT-1 null allele detection was performed by real-time polymerase chain reaction. The frequency of the null GSTT1 genotype (nonexpression or deletion of the homozygous polymorphism of the GSTT1 protein) was 17.9% (n=31 null allele GSTT1/173 total individuals). Our data suggest that the frequency of null GSTT1 mutations in our population in Southeast Spain is 17.9%, lower than in other Caucasoid populations. This would convert our recipient population into more susceptible to nonlocal potential organ donors and less susceptible to local donors. All recipients bearing this GSTT1 deletion homozygous would be without the protein and triggering an alloantigen in the case of transplantation with a donor without deletion.

Evaluation of the relationship between de-novo DSA development and CXCR5+PD-1+CD8+ T cells and PD-1/PD-L1 mRNA expression in kidney transplant recipients.

The relationship between the Follicular Cytotoxic T cell subgroup and expression levels of PD1/PD-L1 genes and the development of donor specific antibody (DSA) is unknown. In this study, we aimed to examine CD8+CXCR5+PD-1+ follicular cytotoxic T cell levels and expression levels of PD1/PD-L1 genes in peripheral blood lymphocytes in de-novo DSA positive and negative kidney transplant recipients (KTR). In our study, expression of PD-1/ PD-L1 genes by Real-Time Quantitative PCR method and CD8+CXCR5+PD-1+ T cell expression levels by flow cytometric method were obtained from peripheral blood samples. 63 participants were included in the study (de-novo DSA positive recipients (n=22, group 1), de-novo DSA negative recipients (n=20, group 2) and healthy control (n=21, group 3). All patients had negative PRA before kidney transplantation. Expression (%) levels of target cells were evaluated by flow cytometry method. IBM SPSS Statistics for Windows Version 22 and R.3.3.2 software were used to evaluate the data. The demographic data of the groups were similar. PD-1 mRNA expression was higher in de-novo DSA positive KTR than negative (respectively, 1.03±.29/.82±.15, p: .001). CD8+CXCR5+PD-1+ T cell expression levels were found to be higher in the de-novo DSA positive group than in the negative group and similar to the healthy group (respectively, 3.06±1.98/.52±.40, p:.001, 3.06±1.98/2.78±.59, p:.62). The percentage of CD8+CXCR5+PD-1+ expressing T cells was significantly lower in the HLA-Class II+ group than other groups (HLA CI/II/ I+II, respectively, 3.63±2.72/1.65±.50/3.68±1.67, p: .04). In our study, a significant relationship was found between DSA formation and PD-1 mRNA level and CD8+CXCR5+PD-1+ follicular cytotoxic T cell in KTR.

Association of positive pre-transplant angiotensin II type 1 receptor antibodies with clinical outcomes in lung transplant recipients

IntroductionAutoantibodies against the angiotensin II type 1 receptor (AT1R-Ab) have been previously associated with de novo donor-specific antibody (DSA) formation in lung transplantation. However, data regarding the clinical significance of AT1R-Ab in long-term graft function after lung transplantation are lacking. MethodsSeventy-one patients who underwent lung transplantation between July 2016 and January 2020 were enrolled in this study. We examined the relationship between pre-transplant AT1R-Ab levels and graft function, clinical outcomes, and human leukocyte antigen (HLA) DSA levels during the first 3 years post-transplantation. ResultsSeventeen (23.9%) patients were AT1R-Ab-positive, and 54 (76.1%) were AT1R-Ab-negative. The median antibody value of the AT1R-Ab-positive group was 18 [18–22.5] U/mL, while that of the AT1R-Ab-negative group was 5.1 [3.5–8.0] U/mL (p < 0.001). There was no significant difference in the median acute cellular rejection (ACR) scores between the two groups (median [interquartile range] 1 [0.8–3] vs. 0.7 [0–1]; p = 0.145). However, there was a significant difference in the distribution of the ACR scores between the two groups (p = 0.015). Most (41.2%) patients in the pre-transplant AT1R-positive group scored above 1. The incidence of de novo DSA was also higher in AT1R-Ab-positive than in AT1R-Ab-negative patients (52.9% vs. 20.4%, p = 0.009). The incidence of chronic lung allograft dysfunction (CLAD) within 3 years was significantly higher in AT1R-Ab-positive than in AT1R-Ab-negative patients (58.3% vs. 11.8%; p < 0.001). In the multivariate Cox regression analysis, AT1R-Ab positivity (hazard ratio, 9.46; 95% confidence interval, 2.89–30.94; p < 0.001) was significantly associated with early CLAD. Furthermore, Kaplan-Meier analysis showed that AT1R-Ab-positive patients had a shorter survival time (χ2 = 39.62, p < 0.001). ConclusionHigh AT1R-Ab levels in the pre-transplant serum of lung recipients were associated with the development of de novo HLA-DSA, ACR, early CLAD, and short survival.

Excellent efficacy and beneficial safety during observational 5-year follow-up of rapid steroid withdrawal after renal transplantation (Harmony FU study).

We previously reported excellent efficacy and improved safety aspects of rapid steroid withdrawal (RSWD) in the randomized controlled 1-year "Harmony" trial with 587 predominantly deceased-donor kidney transplant recipients randomized either to basiliximab or rabbit antithymocyte globulin induction therapy and compared with standard immunosuppressive therapy consisting of basiliximab, low tacrolimus once daily, mycophenolate mofetil and corticosteroids. The 5-year post-trial follow-up (FU) data were obtained in an observational manner at a 3- and a 5-year visit only for those Harmony patients who consented to participate and covered clinical events that occurred from the second year onwards. Biopsy-proven acute rejection and death-censored graft loss rates remained low and independent of RSWD. Rapid steroid withdrawal was an independent positive factor for patient survival (adjusted hazard ratio 0.554, 95% confidence interval 0.314-0.976; P=.041).The reduced incidence of post-transplantation diabetes mellitus in RSWD patients during the original 1-year study period was not compensated by later incidences during FU. Incidences of other important outcome parameters such as opportunistic infections, malignancies, cardiovascular morbidity/risk factors, donor-specific antibody formation or kidney function did not differ during FU period. With all the limitations of a post-trial FU study, the Harmony FU data confirm excellent efficacy and beneficial safety aspects of RSWD under modern immunosuppressive therapy over the course of 5 years after kidney transplantation in an immunologically low-risk, elderly population of Caucasian kidney transplant recipients. Trial registration: Clinical trial registration number: Investigator Initiated Trial (NCT00724022, FU study DRKS00005786).

#3973 EXCELLENT EFFICACY AND BENEFICIAL SAFETY DURING FIVE YEAR FOLLOW-UP OF RAPID STEROID WITHDRAWAL AFTER RENAL TRANSPLANTATION (HARMONY STUDY)

Abstract Background and Aims We previously reported excellent efficacy and improved safety aspects of rapid steroid withdrawal in the randomized controlled one year “Harmony” trial with 587 predominantly deceased-donor kidney transplant recipients randomized either to basiliximab or rabbit antithymocyte globulin induction therapy and compared to standard immunosuppressive therapy consisting of basiliximab, low tacrolimus once daily, mycophenolate mofetil, and corticosteroids. The five-year post-trial follow-up (FU) data reported here were obtained in an observational manner to evaluate, how these excellent short-term surrogate parameters will translate into hard long-term outcome parameters like patient death/graft loss. Method The five-year post-trial follow-up data were obtained in an observational manner at a three and a five-year visit for patients who consented to participate and covered clinical events that occurred from the second year onwards. Results Biopsy-proven acute rejection and death-censored graft loss rates remained low and independent of rapid steroid withdrawal (see Figure 1). Rapid steroid withdrawal was an independent positive factor for patient survival (adjusted hazard ratio 0.554, 95 % confidence interval 0.314 to 0.976; p = 0.041, see Table 1). The reduced incidence of post-transplantation diabetes mellitus in rapid steroid withdrawal patients during the original one-year study period was not compensated by later incidences during follow-up. Incidences of other important outcome parameters such as opportunistic infections, malignancies, cardiovascular morbidity/risk factors, donor specific antibody formation, or kidney function did not differ during follow-up period. Conclusion The Harmony follow-up trial confirms excellent efficacy and beneficial safety aspects of rapid steroid withdrawal under modern immunosuppressive therapy demonstrating for the first time increased patient survival in an immunologically low-risk, elderly population of Caucasian kidney transplant recipients.

Memory T follicular helper cells drive donor-specific antibodies independent of memory B cells and primary germinal center and alloantibody formation

Human leukocyte antigen antibodies are important immunologic mediators of renal allograft loss and are difficult to control. The inability to permanently eliminate donor-specific antibodies (DSA) is partly due to an incomplete understanding of the cellular mechanisms driving alloantibody formation, recurrence, and maintenance. Memory T follicular helper (mTfh) cells rapidly interact with memory B cells upon antigen re-exposure for anamnestic humoral responses, but little is known about Tfh memory in transplantation. We hypothesized that alloreactive mTfh cells form after transplantation and play a critical role in DSA formation following alloantigen re-encounter. To test this hypothesis, we utilized murine skin allograft models to identify and characterize Tfh memory and interrogate its ability to mediate alloantibody responses. We identified alloreactive Tfh memory as a mediator of accelerated humoral alloresponses independent of memory B cells and primary germinal center, or DSA, formation. Furthermore, we demonstrate that mTfh-driven alloantibody formation is susceptible to CD28 costimulation blockade. These findings provide novel insight into a pathologic role for memory Tfh in alloantibody responses and strongly support shifting therapeutic focus from the singular targeting of B cell lineage cells and alloantibodies themselves to multimodal strategies that include inhibition of mTfh cells to treat DSA.

Extracorporeal Photopheresis Suppresses Transplant Fibrosis by Inducing Decorin Expression in Alveolar Macrophages.

Extracorporeal Photopheresis Suppresses Transplant Fibrosis by Inducing Decorin Expression in Alveolar Macrophages.

Genetic Polymorphisms in Follicular Helper T Cell–Related Molecules Predispose Patients to De Novo Donor-Specific Antibody Formation After Kidney Transplantation

Risk prediction of de novo donor-specific antibody (dnDSA) formation is crucial for understanding the long-term prognostic impact of kidney transplantation (KT). Recently, follicular helper T (Tfh) cells, a subtype of CD4+ T cells, have been reported to play an important role in dnDSA formation after solid organ transplantation. Given the growing recognition of the importance of Tfh cells in generating a strong humoral immune response, we examined whether polymorphisms in Tfh cell-related molecules were associated with dnDSA formation after KT. Eighty-three patients who underwent living-donor KT between January 2013 and February 2020 at Hiroshima University Hospital were included in the study. Six Tfh cell-related molecules (BCL6, CXCR5, CXCL13, ICOS, CD40L, and IL21) that are important for Tfh cell differentiation and maturation in secondary lymphoid tissues were investigated. CTLA4, which is important for Tfh-cell activation, was also investigated. Single nucleotide polymorphisms (SNPs) in the genes for these molecules were detected using Taq Man SNP genotyping and evaluated for their association with dnDSA formation after KT. Of the 83 KT recipients, 8 developed dnDSAs during the observation period. No statistically significant differences were observed in the baseline characteristics between patients with and without dnDSA formation, except for donor age. Among the 7 Tfh cell-related molecules, the incidence of dnDSA formation was associated with CXCR5 and CTLA4 SNPs. Furthermore, combining these 2 SNPs enabled more significant stratification of dnDSA formation. Our findings indicate that genetic polymorphisms in Tfh cell-related molecules are predisposing factors for dnDSA formation after KT.