HLA-DQ Donor-specific Antibodies Research Articles

HLA-DQ-Specific Recombinant Human Monoclonal Antibodies Allow for In-Depth Analysis of HLA-DQ Epitopes.

HLA-DQ donor-specific antibodies (DSA) are the most prevalent type of DSA after renal transplantation and have been associated with eplet mismatches between donor and recipient HLA. Eplets are theoretically defined configurations of surface exposed amino acids on HLA molecules that require verification to confirm that they can be recognized by alloantibodies and are therefore clinically relevant. In this study, we isolated HLA-DQ specific memory B cells from immunized individuals by using biotinylated HLA-DQ monomers to generate 15 recombinant human HLA-DQ specific monoclonal antibodies (mAb) with six distinct specificities. Single antigen bead reactivity patterns were analyzed with HLA-EMMA to identify amino acids that were uniquely shared by the reactive HLA alleles to define functional epitopes which were mapped to known eplets. The HLA-DQB1*03:01-specific mAb LB_DQB0301_A and the HLA-DQB1*03-specific mAb LB_DQB0303_C supported the antibody-verification of eplets 45EV and 55PP respectively, while mAbs LB_DQB0402_A and LB_DQB0602_B verified eplet 55R on HLA-DQB1*04/05/06. For three mAbs, multiple uniquely shared amino acid configurations were identified, warranting further studies to define the inducing functional epitope and corresponding eplet. Our unique set of HLA-DQ specific mAbs will be further expanded and will facilitate the in-depth analysis of HLA-DQ epitopes, which is relevant for further studies of HLA-DQ alloantibody pathogenicity in transplantation.

Clinical Outcome of Kidney Transplant Patients on the Allograft Function, Loss, Effects of HLA-DQB1-DSA+, and Graft Survival

Matching for HLA-DQB1 molecules and anti-DQ donor-specific antibodies (DSAs) has been less studied to allocate transplants from deceased donors in developed countries. The aim of this study was to evaluate the clinical outcome of 519 kidney transplant recipients on the allograft function, loss, and survival and with emphasis on effects of HLA-DQB1-DSA+ at minimum of 10 years' follow-up. Five hundred nineteen kidney transplant patients were allocated into 3 groups (G) by immunologic profiles, namely, G1 (SPI-SAB HLA-DQ negative [DQ-]), G2 (SPI-SAB HLA-DQ positive DSA negative [DQ+/DSA-]), and G3 (SPI-SAB HLA-DQ DSA positive [DQ+ DSA+]), and the outcomes were reported until 10 years after transplantation. The proportion of rejection episodes was higher in G3 (25.0% and 26.32%, respectively) than in G1 (8.63% and 6.82%, respectively) and G2 (10.0% and 0%, respectively; P=.047 and P=.014, respectively). In G3, 3 patients lost their grafts by antibody-mediated rejection. Patients who received kidneys from deceased donors (G3) showed worse graft survival rates than those from G1 donors (P=.001). Patients from G3 had a 2.18-fold higher risk of graft loss than patients from G1 (P=.028). Allograft function was worse in G3 than in G2 or G1, and graft losses were more frequent by T-cell-mediated rejection in G1, and graft losses by antibody-mediated rejection were similar in G1 and G3 due to HLA class I (A1, 11 and B 8, 52) and HLA class II by DR7 and DQ 2, 5, 9 DSA, respectively. Allograft survival decreased in patients with HLA-DQB1 DSA. The risk of graft loss was 1.75-fold that in patients who received transplants from living donors.

Impact of the immunotherapy induction on allograft outcome and survival in kidney transplant patients with donor-specific antibodies to HLA-DQB1

BackgroundThe presence of donor-specific antibodies (DSAs) against HLA-DQB1 is considered a significant barrier to good outcome and allograft survival in kidney transplantation (KT). This study aimed to assess the impact of induction immunotherapy on the outcome and allograft survival in KT patients with HLA-DQB1-DSA. MethodologyThirty-two patients who had undergone KT and found to be positive for HLA-DQB1-DSA were monitored at least one to 10 years. They were allocated into two groups of patients: G1 received induction immunotherapy (n = 14 patients; 43.75%), and G2 did not (n = 18 patients; 56.25%). ResultsIn G1, 6 (42.86%) patients experienced rejection episodes (RE), 2 (14.29%) due to antibody-mediated rejection (ABMR) and 4 (28.57%) due to T-cell-mediated rejection (TCMR). In G2, 13 (72.22%) patients experienced RE, 3 (16.67%) due to ABMR, and 10 (55.56%) due to TCMR. Graft loss occurred in 4 patients from G1, 2 (14.29%) due to ABMR and 2 (14.29%) due to non-immunological causes. In G2, 9 (50.00%) patients lost their grafts, 2 (11.11%) due to TCMR, 2 (11.11%) due to ABMR, and 5 (27.78%) due to non-immunological causes. The graft survival rate was 64.29% in G1 and 45.83% in G2. Glomerulitis and peritubular capillaritis were observed in 3 and C4d-positive patients with/or without induction who lost their grafts by ABMR by HLA-DQ DSA. Two patients from G2 lost their graft by TCMR due to interstitial lymphocytic infiltrate (i1), foci of mild tubulitis (t2), interstitial edema, moderate interstitial fibrosis and tubular atrophy. Better graft survival rates were shown in patients from G1 who received induction immunotherapy. ConclusionOur study suggests that patients with an immunological profile of HLA-DQ+ DSA+ treated by immunotherapy induction have a decreased risk of ABMR and increased allograft survival, and the presence of anti-HLA-DQB1 DSA+ detected before and after KT were associated with ABMR episodes and failure.

The Clinical Impact of Preformed HLA-DQ Donor-Specific Antibodies on Graft Outcomes in Kidney Transplantation

The Clinical Impact of Preformed HLA-DQ Donor-Specific Antibodies on Graft Outcomes in Kidney Transplantation

A Mismatch Made in Medicine: Potential Implications of HLA DQ Epitope Mismatching Following Heart Transplantation

Long term heart allograft survival is negatively impacted by the presence of donor specific antibodies (DSA). HLA-DQ DSA have been associated with reduced graft survival in non-heart allografts, and recent studies have indicated that HLA DR/DQ epitope mismatches may be utilized as a potential prognostic marker for de novo DSA development and subsequent graft loss in the kidney transplant population. Few studies have evaluated the presence of DQ DSA in the heart transplantation population and even fewer have examined the prognostic implications of epitope mismatches. Here, in a single center analysis, we retrospectively examine the incidence and impact of de novo DQ DSA development and the corresponding number of epitope mismatches in three adult cohorts at 1-3 years, 5 years and 10 years after heart transplantation. De-novo DQ DSA was present in 24/146 (16%) of patients transplanted at 1-3 years, 7/43 (16%) patients at 5 years and 11/46 (24%) patients at 10 years after transplant. While DQ DSA was seen more frequently in patients 10 years post-transplant, the average number of donor-recipient DQ epitope mismatches was similar (average of 23) in all groups. The presence of DQ DSA was associated with rejection, defined as biopsy-proven AMR or CAV, in 17/24 (71%) of patients at 1-3 years, 6/7 (86%) patients at 5 years and 10/11 (91%) patients at 10 years. Within each cohort, patients with greater than 20 DQ epitope mismatches were more prone to developing rejection. Immunosuppression after transplantation was protocolized and consisted of tacrolimus, mycophenolate mofetil, and an oral prednisone taper. Patients with documented medical noncompliance or subtherapeutic immunosuppression levels were not included in our analysis. While our study was underpowered to demonstrate statistical significance, our trends showed that within each cohort, in the presence of therapeutic levels of immunosuppression, patients with development of de novo DQ DSA and with a higher number of DQ epitope mismatches (greater than 20) were more prone to developing biopsy-proven AMR or CAV. Further research is required for validation. If these findings are indeed confirmed with larger studies, they could have important clinical implications that could help tailor individual immunosuppression regimens and risk-stratification strategies.

SP791The role of lymphocyte crossmatch testing in de novo HLA-DQ donor-specific antibody positive renal transplant recipients

SP791The role of lymphocyte crossmatch testing in de novo HLA-DQ donor-specific antibody positive renal transplant recipients

HLA-DQ alloantibodies directly activate the endothelium and compromise differentiation of FoxP3high regulatory T lymphocytes

Development of donor-specific antibodies is associated with reduced allograft survival in renal transplantation. Recent clinical studies highlight the prevalence of human leukocyte antigen (HLA)-DQ antibodies amongst de novo donor-specific antibodies (DSAs), yet the specific contribution of these DSAs to rejection has not been examined. Antibody-mediated rejection primarily targets the microvasculature, so this study explored how patient HLA-DQ alloantibodies can modulate endothelial activation and so immunoregulation. HLA-DQ antibodies phosphorylated Akt and S6 kinase in microvascular endothelial cells. This activation prior to culture with alloreactive lymphocytes increased IL-6 and RANTES secretion. The antibody-mediated upregulation of IL-6 was indeed Akt-dependent. The binding of HLA-DQ antibodies to endothelial cells selectively reduced T cell alloproliferation and FoxP3high Treg differentiation. In clinical studies, detection of HLA-DQ DSAs with other DSAs is associated with worse graft survival than either alone. Endothelial cells stimulated with HLA-DR and HLA-DQ antibodies showed a synergistic increase in pro-inflammatory cytokine secretion and a decrease in Treg expansion. HLA-DQ antibodies strongly promote pro-inflammatory responses in isolation and in combination with other HLA antibodies. Thus, our data give new insights into the pathogenicity of HLA-DQ DSAs.

HLA-DQ Specific Alloantibodies Modify Allogenic Endothelial Cell Immunogenicity and Impair the Expansion of Anti-Inflammatory FoxP3 High Regulatory T Lymphocytes

Recent clinical studies have highlighted the prevalence of de novo circulating Donor-Specific Antibodies (DSA) against HLA-DQ following solid organ transplantation. The emergence of HLA-DQ DSA has been associated with poor graft outcome. The allograft microvascular endothelium is known to upregulate HLA-DQ expression during rejection. The allograft endothelium is directly exposed to circulating anti-donor antibodies and as a result, becomes a principal site of DSA binding and thereby the target of antibody-mediated damage. Endothelial activation is a feature of antibody-mediated rejection and is reported to arise from inflammation, DSA binding and complement activation. Activated endothelial cells modulate the recipient’s immune response as a result of their interactions with CD4+ T lymphocytes. Plasmapheresis samples were obtained from alloimmunized patients with high levels of circulating DSA. Antibodies were isolated using protein G beads, and their HLA specificity was assessed by Luminex. Antibodies were evaluated for binding to microvascular endothelial cells, and a time course of binding was established by flow cytometry. Patient antibodies specific for relevant HLA-DQ alleles were used to assess potential signal transduction from antibody-binding to endothelial cells. HLA-DQ DSA induced transient phosphorylation of Akt and S6 Kinase. This was confirmed using a monoclonal anti-HLA DQ antibody. Alloantibodies against HLA-DQ alleles not expressed by our cell model did not induce specific signalling events. Previously, we found that HLA-DR+ endothelial cells are capable of inducing alloproliferation of CD4+ T lymphocytes and selectively expanding Th17 and FoxP3high T regulatory cell (Treg) subsets (Taflin PNAS 2011, Lion Am J Transplant 2016). The presence of intragraft Th17 correlates with shorter graft survival, whilst the proportion of Treg cells has been implicated in tolerance. To assess the functional consequences of DSA binding, endothelial cells were stimulated with HLA-DQ DSA for one hour preceding co-culture with allogenic peripheral blood mononuclear cells. After seven days, CD4+ T cell subsets were analysed by intracellular cytokine staining. HLA-DQ DSA modified endothelial cell immunogenicity, resulting in a reduction in alloproliferation and in Treg expansion. Alloantibodies against HLA-DQ alleles not expressed by our cell model did not alter alloproliferation or Treg expansion. The impaired amplification of anti-inflammatory Treg cells, in combination with an unaltered expansion of the Th17 subset, leads to an overall pro-inflammatory orientation of alloreactive CD4+ T cells. This altered composition of CD4+ T cells, due to HLA-DQ binding to endothelial cells, may exacerbate allograft damage and reduce allograft tolerance. AC was supported by the Société Francophone de Transplantation (SFT).

It’s HLA-DR Not HLA-DQ Donor-specific Antibody That is Correlated to CAV After Heart Transplant

Class II donor specific anti-HLA antibodies (DSA) have been correlated to subsequent CAV development. More specifically, HLA-DQ has been most reported for CAV development. Recently, HLA-DP has been added to the UNET computer. In this recent era, we are now able to compare class II antibodies to one another and assess outcome. We chose to evaluate our HTx patients who developed class II DSA in the first year after transplant.

Donor-specific HLA-DQ antibodies may contribute to poor graft outcome after heart transplantation.

BACKGROUNDHLA-DQ donor-specific antibodies (DSA) are implicated in allograft dysfunction after renal and lung transplantation. Limited data exists on the impact of HLA-DQ antibodies on heart transplant patients.OBJECTIVETo investigate the impact of DSA formation on allograft function and outcomes in heart transplant patients.DESIGNRetrospective cohort study.SETTINGCollating post-transplantation patient data from computerized database in a tertiary hospital in Riyadh, Saudi Arabia from January 2006 to October 2014.PATIENTS AND METHODSWe excluded recipients with positive preoperative complement-dependent-cytotoxicity crossmatch grafts and those with preformed DSA. Anti-HLA antibodies were identified using Luminex-based assay in sera collected before transplantation with a routine endomyocardial biopsy the first year and then annually.MAIN OUTCOME MEASURESPrimary outcome measures were all-cause mortality, development of antibody mediated rejection, treated acute cellular rejection (ACR) and cardiac allograft vasculopathy (CAV).SAMPLE SIZE127 patients.RESULTSDSA formation occurred in 43/127 (34%), with 33/43 (77%) targeting HLA-DQ antigens alone (n=7) or in combination with -DR, -A or B antibodies (n=26). Most (76%) were male and the mean (SD) age was 36 (14) years. Ten patients developed -A, -B or -DR antibodies without -DQ antibodies also present. Treated ACR (P=.011), reduced left ventricular ejection fraction (P<.001), CAV development (P=.003), and all-cause mortality (P=.01) were all significantly more prevalent in the DSA-positive cohort.CONCLUSIONHLA-DQ donor-specific antibodies were the most common type detected and may play a significant role in poor outcomes post-cardiac transplantation. This emphasizes the importance of HLA-DQ matching and monitoring for DSA formation in order to minimize post-transplantation immunological risk.LIMITATIONSRetrospective design comes with inherent biases, results from single institute, with a particularly young cohort.

P084 De novo HLA-DQ donor specific antibodies are associated with worse long term allograft survival after lung transplantation

Aim The long term graft survival of lung transplantation remains significantly worse than any other solid organ transplants. De novo HLA donor specific antibodies (dnDSA) have been implicated with antibody-mediated rejection (AMR), a recognized cause of allograft dysfunction in lung transplant recipients. It remains unclear what dnDSA against specific HLA antigens play in long term graft function and patient survival. We have observed that HLA class II dnDSA are common in lung transplant recipients. In this study, we further characterized that HLA dnDSA implicated allograft function and recipient survival. Methods We retrospectively investigated lung transplant recipients received transplantation between Jan, 2004 and December, 2015 in a single center. HLA DSA were tested using Luminex LabSceeen single antigen bead assays per recipient’s clinical indications. Graft function and patient survival were followed up until December 31, 2016. Data were analyzed using cox hazards regression model and logistic regression. Results A total of 187 patients were followed up for a median of 2.67 years (1–12 years). Among them, 54% were female and 46%, male and 78% were Caucasians. Fifty-eight (31%) patients developed dnDSA, i.e., 8 (4.2%) class I, 42 (22.4%) class II and 8 (4.2%) class I and class II DSA, respectively. Among these DSA positive patients, 36 (62%) patients developed HLA-DQ DSA. Both Class II dnDSA and/or DQ DSA were significantly associated with worse allograft survival and patient survival (P Conclusions HLA-DQ dnDSA are dominate in lung transplant recipients after transplantation which are associated with worse long term allograft and recipient survival. To prevent HLA-DQ dnDSA by better HLA-DQ match or to properly treat patients with HLA-DQ dnDSA may improve long term outcomes for lung transplant recipients.

Donor Specific Antibodies are not only directed against HLA-DR: Minding your Ps and Qs

During solid organ transplantation, interactions between recipient and donor immune cells occur chiefly in the allograft microvasculature. All three HLA class II antigens, DR, DP and DQ, have been detected on renal EC with a markedly increased expression of HLA class II observed in renal allografts undergoing rejection. Recent studies of donor-specific antibodies (DSA) have exposed the prevalence of de novo DSA directed against HLA-DQ, as well as a strong association between these antibodies and allograft damage. The HLA-DQ molecule can be distinguished from the other class II antigens by its transcription, expression and peptide repertoire. The distinct intragraft expression and immunogenicity of HLA-DQ may contribute to the incidence of HLA-DQ DSA, as well as directing the DSA-mediated damage. The possibility of HLA class II antigen-specific signaling in EC may reveal different mechanisms of allograft damage that act in tandem with complement-dependent injury. This review addresses the features of the HLA-DQ heterodimer that may underlie the high incidence of HLA-DQ directed DSA and their association with allograft damage. We also consider existing data in hematopoietic stem cell transplantation concerning HLA directed DSA.

Alloantibody Responses After Renal Transplant Failure Can Be Better Predicted by Donor-Recipient HLA Amino Acid Sequence and Physicochemical Disparities Than Conventional HLA Matching.

We have assessed whether HLA immunogenicity as defined by differences in donor–recipient HLA amino‐acid sequence (amino‐acid mismatch score, AMS; and eplet mismatch score, EpMS) and physicochemical properties (electrostatic mismatch score, EMS) enables prediction of allosensitization to HLA, and also prediction of the risk of an individual donor–recipient HLA mismatch to induce donor‐specific antibody (DSA). HLA antibody screening was undertaken using single‐antigen beads in 131 kidney transplant recipients returning to the transplant waiting list following first graft failure. The effect of AMS, EpMS, and EMS on the development of allosensitization (calculated reaction frequency [cRF]) and DSA was determined. Multivariate analyses, adjusting for time on the waiting list, maintenance on immunosuppression after transplant failure, and graft nephrectomy, showed that AMS (odds ratio [OR]: 1.44 per 10 units, 95% CI: 1.02–2.10, p = 0.04) and EMS (OR: 1.27 per 10 units, 95% CI: 1.02–1.62, p = 0.04) were independently associated with the risk of developing sensitization to HLA (cRF > 15%). AMS, EpMS, and EMS were independently associated with the development of HLA‐DR and HLA‐DQ DSA, but only EMS correlated with the risk of HLA‐A and ‐B DSA development. Differences in donor–recipient HLA amino‐acid sequence and physicochemical properties enable better assessment of the risk of HLA‐specific sensitization than conventional HLA matching.

Deleterious effect of DQ donor specific antibody on chronic and acute rejection following lung transplant exacerbated by antibody to protein kinase C-[formula omitted

Background HLA-DQ Donor Specific Antibody (DSA) is implicated in the negative impact of allograft function after lung transplantation. Non-HLA antibody to Protein Kinase C- ζ [(PKC- Z ) Ab] was reported to associate with graft injury in the absence of C4d deposition. Here we demonstrate DQ DSAs on chronic and acute graft injury elevated by (PKC- Z ) Ab following lung transplants. Case Report A 28-yo old male patient with cystic fibrosis underwent 1st Bilateral Lung Transplant (BLT) in 8/2011 with negative HLA DSA and cross-matches. Low titer (PKC- Z ) Ab was detectable. Graft function performed well in room air after BLT. In 9/2011 bronchoscopy biopsy showed A1B1 along with the appearance of DQ6 de novo DSA, but both biopsy and DSA turned negative following prednisone taper treatment. In 10/2014, he was admitted for cellular and antibody mediated rejection (CMR and AMR) with bronchoscopy biopsy A3B2R and significant increase of DQ6 without C4d deposition. At that time, (PKC- Z ) Ab was unchanged. One month later, (PKC- Z ) Ab abruptly increased to around 2.5-fold and DQ6 peaked (Fig. 1A1, A2). Patient lost allograft and received 2nd BLT on 11/19/2014 with negative cross-matches, DQ9 preformed DSA, and high titer (PKC- Z ) Ab. He was readmitted in 3/2015 for aggressive therapy for acute AMR with ×5 plasmapheresis, rituximab and bortezomib, and IVIG ×5 due to the significant drop of allograft function. AMR was aborted with remarkable decline of DQ9 DSA and (PKC- Z ) Ab on 4/21/2015 (Fig. 1B1, B2) resulting in improved graft function. Summary De novo DQ6 DSA with concurrent CMR resulted in chronic allograft rejection while preformed DQ9 DSA lead to acute allograft rejection after HLT. This negative impact of DQ DSAs to lung allograft injury and/or dysfunction was exacerbated by high titer (PKC- Z ) Ab. Download : Download full-size image

The Role of Immunoglobulin-G Subclasses and C1q in De Novo HLA-DQ Donor-Specific Antibody Kidney Transplantation Outcomes

Anti-HLA-DQ antibodies are the predominant HLA class II donor-specific antibodies (DSAs) after transplantation. Recently, de novo DQ DSA has been associated with worse allograft outcomes. The aim of this study was to determine the further complement-binding characteristics of the most harmful DQ DSA. Single-antigen bead technology was used to screen 284 primary kidney transplant recipients for the presence of posttransplantation DQ DSA. Peak DSA sera of 34 recipients with only de novo DQ DSA and of 20 recipients with de novo DQ plus other DSAs were further analyzed by a modified single-antigen bead assay using immunoglobulin (Ig)-G subclass-specific reporter antibodies and a C1q-binding assay. Compared with recipients who did not have DSA, those with de novo persistent DQ-only DSA and with de novo DQ plus other DSAs had more acute rejection (AR) episodes (22%, P=0.005; and 36%, P=0.0009), increased risk of allograft loss (hazards ratio, 3.7, P=0.03; and hazards ratio, 11.4, P=0.001), and a lower 5-year allograft survival. De novo DQ-only recipients with AR had more IgG1/IgG3 combination and C1q-binding antibodies (51%, P=0.01; and 63%, P=0.001) than patients with no AR. Furthermore, the presence of C1q-binding de novo DQ DSA was associated with a 30% lower 5-year allograft survival (P=0.003). The presence of de novo persistent, complement-binding DQ DSA negatively impacts kidney allograft outcomes. Therefore, early posttransplantation detection, monitoring, and removal of complement-binding DQ might be crucial for improving long-term kidney transplantation outcomes.

Increased Frequency of Class II HLA-DQ Donor-Specific Antibodies Is Associated with Mixed Cellular and Humoral Rejection in Lung Transplantation

Purpose The significance of donor-specific HLA antibodies (DSA) in lung transplantation (LTx) has emerged with the introduction of solid phase assays for antibody detection. Using ELISA based screening we have shown that 14% of LTx had de novo DSA and most (78%) developed chronic allograft rejection vs. 24% in patients without DSA. Further evaluation of DSA with Luminex (L) based methods for screening, specificity and functional analysis is needed to determine the impact of pre-formed and de-novo DSA on outcome. Methods and Materials Patients who were transplanted January 2011 to July 2012 and were screened prospectively for DSA with L-PRA were included in the analysis. The screening included samples pre-Tx and post LTx at 1 month and every 2 months in conjunction with surveillance and clinical bronchoscopies. The specificity of DSA and strengths (MFI) determined with single antigen beads (L-IgG) and complement binding with L-C1q- assay (L-C1q) was associated with cellular rejection and antibody mediated rejection. Results This study was done on 149 consecutive LTx with a minimum follow-up of 3 months and adequate DSA screening. All had negative CDC T and B cell crossmatches. 5% had DSA pre-Tx that persisted post-Tx and 23% had de-novo DSA within 3-6 months post LTx. Overall, 55% of LTx had high grade ACR; de-novo DSA was higher in ACR (22/82, 27%) vs. no ACR (5/67, 7%) (p 70%) de-novo DSA were HLA-DQ specific including Ab towards DQB, DQA and combination of DQB/DQA pairs. Severe ACR (n=4) with DSA and C1q reactivity was treated with plasmapheresis, IVIG and Rituximab for AMR. Patients with ACR and low level or declining DSA that had a transient or no C1q reactivity (n=19) were not treated for AMR. DSA in LTx without ACR were also low level, transient and without C1q reactivity. Conclusions The frequency of de-novo DSA is higher than previously reported. Persistent, high grade ACR with C1q binding class II HLA-DQ DSA was associated with AMR.

Donor-specific HLA-DQ antibodies may contribute to poor graft outcome after renal transplantation

Increasing evidence suggests a detrimental effect of donor-specific antibodies directed against the human leukocyte antigen (HLA)-A, -B, and -DR loci on renal allograft outcomes. Limited data exist on the impact of de novo HLA-DQ antibodies. Over a 3-year period, we prospectively monitored 347 renal transplant recipients without pre-transplant donor-specific antibodies for their development de novo. After 26 months of follow-up, 62 patients developed donor-specific antibodies, of which 48 had a HLA-DQ antibody either alone (33 patients) or in combination with an HLA-A, -B, or -DR antibody (15 patients). Only 14 patients developed a donor-specific HLA-A, -B, or -DR antibody without a HLA-DQ antibody present. Acute rejection occurred in 21% of the HLA-DQ-only patients, insignificant when compared with 11% of patients without donor-specific antibodies. At the last follow-up, the mean serum creatinine and the fraction of patients with proteinuria were significantly higher in those that developed only HLA-DQ than those without antibodies. The 3-year graft survival was significantly worse when HLA-DQ antibodies were combined with non-DQ antibodies (52%) compared with HLA-DQ alone, non-DQ antibodies alone, or no antibodies (92-94%). Thus, our prospective monitoring study found that donor-specific HLA-DQ antibodies were the most common type detected and these antibodies may contribute to inferior graft outcomes. Ongoing surveillance is necessary to determine the long-term outcome of patients developing HLA-DQ donor-specific antibodies.

Expansion of Humoral Donor-Specific Alloreactivity After Renal Transplantation Correlates With Impaired Graft Outcome

IgG human leukocyte antigen (HLA) antibodies were investigated retrospectively after transplantation in 264 primary renal graft recipients. All patients who developed de novo donor-specific antibodies (DSA) and non-DSA (NDSA) ( n = 40, 15.1%) were divided into two groups. Group A consisted of patients ( n = 20) with stable good graft function (GGF), and group B consisted of patients ( n = 20) who developed rejection and/or graft failure (R/GF). DSA were detected in 23 patients (57.5%). Expansion of humoral alloreactivity with the presence of DSA to more than one graft mismatched antigens and coexistence of HLA class I and II DSA were significantly correlated only with R/GF ( p = 0.01). Limitation of alloreactivity to one graft-mismatched antigen was detected mainly in patients with GGF. HLA-DQ DSA alone was found only in patients with GGF ( p = 0.1). No significant differences were found between the two patient groups with NDSA. Expansion of the humoral alloreactivity to more than one graft molecule in renal transplant recipients identifies patients at high risk of rejection or graft failure. Limitation of humoral alloreactivity to one graft antigen perhaps associates the presence of regulatory mechanisms with GGF only in specific cases.

Allelic variation in transcription modulates MHC class II expression and function

During solid organ transplantation, interactions between recipient and donor immune cells occur chiefly in the allograft microvasculature. All three HLA class II antigens, DR, DP and DQ, have been detected on renal EC with a markedly increased expression of HLA class II observed in renal allografts undergoing rejection. Recent studies of donor-specific antibodies (DSA) have exposed the prevalence of de novo DSA directed against HLA-DQ, as well as a strong association between these antibodies and allograft damage. The HLA-DQ molecule can be distinguished from the other class II antigens by its transcription, expression and peptide repertoire. The distinct intragraft expression and immunogenicity of HLA-DQ may contribute to the incidence of HLA-DQ DSA, as well as directing the DSA-mediated damage. The possibility of HLA class II antigen-specific signaling in EC may reveal different mechanisms of allograft damage that act in tandem with complement-dependent injury. This review addresses the features of the HLA-DQ heterodimer that may underlie the high incidence of HLA-DQ directed DSA and their association with allograft damage. We also consider existing data in hematopoietic stem cell transplantation concerning HLA directed DSA.