Graft-protective role of high pretransplantation IgA-anti-Fab autoantibodies: confirmatory evidence obtained in more than 4000 kidney transplants. The Collaborative Transplant Study

Outcome-based Risk Assessment of Non-HLA Antibodies in Heart Transplantation: A Systematic Review

BACKGROUND

Current monitoring after heart transplantation (HT) employs repeated invasive endomyocardial biopsies (EMB). Although positive EMB confirms rejection, EMB fails to predict impending, subclinical, or EMB-negative rejection events. While non-human leukocyte antigen (non-HLA) antibodies have emerged as important risk factors for antibody-mediated rejection after HT, their use in clinical risk stratification has been limited. A systematic review of the role of non-HLA antibodies in rejection pathologies has the potential to guide efforts to overcome deficiencies of EMB in rejection monitoring.

METHODS

Databases were searched to include studies on non-HLA antibodies in HT recipients. Data collected included the number of patients, type of rejection, non-HLA antigen studied, association of non-HLA antibodies with rejection, and evidence for synergistic interaction between non-HLA antibodies and donor-specific anti-human leukocyte antigen antibody (HLA-DSA) responses.

RESULTS

A total of 56 studies met the inclusion criteria. Strength of evidence for each non-HLA antibody was evaluated based on the number of articles and patients in support versus against their role in mediating rejection. Importantly, despite previous intense focus on the role of anti-major histocompatibility complex class I chain-related gene A (MICA) and anti-angiotensin II type I receptor antibodies (AT1R) in HT rejection, evidence for their involvement was equivocal. Conversely, the strength of evidence for other non-HLA antibodies supports that differing rejection pathologies are driven by differing non-HLA antibodies.

CONCLUSIONS

This systematic review underscores the importance of identifying peri-HT non-HLA antibodies. Current evidence supports the role of non-HLA antibodies in all forms of HT rejection. Further investigations are required to define the mechanisms of action of non-HLA antibodies in HT rejection.

Set Up for Failure: Pre-Existing Autoantibodies in Lung Transplant

Lung transplant patients have the lowest long-term survival rates compared to other solid organ transplants. The complications after lung transplantation such as primary graft dysfunction (PGD) and ultimately chronic lung allograft dysfunction (CLAD) are the main reasons for this limited survival. In recent years, lung-specific autoantibodies that recognize non-HLA antigens have been hypothesized to contribute to graft injury and have been correlated with PGD, CLAD, and survival. Mounting evidence suggests that autoantibodies can develop during pulmonary disease progression before lung transplant, termed pre-existing autoantibodies, and may participate in allograft injury after transplantation. In this review, we summarize what is known about pulmonary disease autoantibodies, the relationship between pre-existing autoantibodies and lung transplantation, and potential mechanisms through which pre-existing autoantibodies contribute to graft injury and rejection.

Immune Responses of HLA Highly Sensitized and Nonsensitized Patients to Genetically Engineered Pig Cells

BACKGROUND

We investigated in vitro whether HLA highly sensitized patients with end-stage renal disease will be disadvantaged immunologically after a genetically engineered pig kidney transplant.

METHODS

Blood was drawn from patients with a calculated panel-reactive antibody (cPRA) 99% to 100% (Gp1, n = 10) or cPRA 0% (Gp2, n = 12), and from healthy volunteers (Gp3, n = 10). Serum IgM and IgG binding was measured (i) to galactose-α1-3 galactose and N-glycolylneuraminic acid glycans by enzyme-linked immunosorbent assay, and (ii) to pig red blood cell, pig aortic endothelial cells, and pig peripheral blood mononuclear cell from α1,3-galactosyltransferase gene-knockout (GTKO)/CD46 and GTKO/CD46/cytidine monophosphate-N-acetylneuraminic acid hydroxylase-knockout (CMAHKO) pigs by flow cytometry. (iii) T-cell and B-cell phenotypes were determined by flow cytometry, and (iv) proliferation of T-cell and B-cell carboxyfluorescein diacetate succinimidyl ester-mixed lymphocyte reaction.

RESULTS

(i) By enzyme-linked immunosorbent assay, there was no difference in IgM or IgG binding to galactose-α1-3 galactose or N-glycolylneuraminic acid between Gps1 and 2, but binding was significantly reduced in both groups compared to Gp3. (ii) IgM and IgG binding in Gps1 and 2 was also significantly lower to GTKO/CD46 pig cells than in healthy controls, but there were no differences between the 3 groups in binding to GTKO/CD46/CMAHKO cells. (iii and iv) Gp1 patients had more memory T cells than Gp2, but there was no difference in T or B cell proliferation when stimulated by any pig cells. The proliferative responses in all 3 groups were weakest when stimulated by GTKO/CD46/CMAHKO pig peripheral blood mononuclear cell.

CONCLUSIONS

(i) End-stage renal disease was associated with low antipig antibody levels. (ii) Xenoreactivity decreased with increased genetic engineering of pig cells. (iii) High cPRA status had no significant effect on antibody binding or T-cell and B-cell response.

Pre- and Posttransplant IgA Anti-Fab Antibodies to Predict Long-term Kidney Graft Survival

OBJECTIVES

Immunologic factors are reliable markers for allograft monitoring, because of their seminal role in rejection process. One of these factors is the immunoglobulin (Ig)A anti-Fab of the IgG antibody. This study aimed to evaluate the predictive value of pre- and posttransplant levels of this marker for kidney allograft function and survival.

METHODS

Sera samples of 59 living unrelated donor kidney recipients were collected before and after transplantation (days 7, 14, and 30) and investigated for IgA anti-Fab of IgG antibody levels using enzyme-linked immunosorbent assay in relation with allograft outcome.

RESULTS

Among 59 patients, 15 cases (25%) including 10 with acute rejection and 5 with chronic rejection episodes showed graft failure during a mean of 5 years of follow-up. High posttransplant levels of IgA anti-Fab antibodies were observed more frequently in patients with stable graft function (SGF) compared with patients with graft failure (P = 2 × 10(-6)). None of patients with acute or chronic rejection episodes had high levels of IgA anti-Fab antibodies at day 30 posttransplant compared with the SGF group (P = 10(-6) and P = .01, respectively). In addition, high levels of IgA anti-Fab antibody correlated with lesser concentration of serum creatinine at 1 month posttransplantation (P = .01). Five-year graft survival was associated with high levels of pre- and posttransplant IgA anti-Fab antibodies (P = .02 and P = .003, respectively).

CONCLUSIONS

Our findings indicate the protective effect of higher levels of IgA anti-Fab antibodies regarding to kidney allograft outcomes and long-term graft survival.

Significance of true-positive and false-positive pretransplantation lymphocytotoxic crossmatch in primary liver allograft outcomes

BACKGROUND

At the time of transplantation, a recipient's serum is tested against the prospective donor's lymphocytes to identify specific reactivity and to look for a donor-specific crossmatch (CXM). Here, we investigated the relationship between the pretransplantation lymphocytotoxic CXM results and the long-term outcome of liver transplantation at a single center.

METHODS

From October 1998 to April 2011, medical records, laboratory data, and pretransplantation lymphocytotoxic CXM results were collected from 1133 consecutive liver transplant recipients.

RESULTS

We performed liver transplantations on 80 (7.1%) patients after a true-positive CXM (t+CXM). The t+CXM group exhibited higher initial aminotransferase levels immediately after transplantation compared with a negative CXM group. However, no significant differences in rejection, biliary or vascular complications, viral disease recurrence, or de novo malignancies were found. Although overall graft and patient survival did not differ between the groups, liver-specific graft survival was inferior in the t+CXM group. It was also found that, in 42 (3.7%) recipients, initially positive results converted to final negative results after the elimination of immunoglobulin M autoantibodies. We defined this subpopulation as a false-positive CXM. Significantly decreased posttransplantation aminotransferase levels with a higher incidence of de novo malignancies were observed in this group compared with negative controls.

CONCLUSION

Our findings demonstrate that t+CXM transplants show increased aspartate aminotransferase and alanine aminotransferase peak immediately after transplantation, which influences liver-specific graft outcomes. Additionally, the presence of circulating immunoglobulin M autoantibodies against recipients' own antigens may be protective in liver grafts. However, this may be a predisposing factor for de novo malignancies.

Kidney graft recipients with pretransplantation HLA CLASS I antibodies and high soluble CD30 are at high risk for graft loss

In the present study, we investigated whether pretransplantation HLA class I and class II antibodies and pretransplantation levels of soluble CD30 (sCD30) and IgA anti-Fab autoantibodies are predictive of kidney allograft survival. Pretransplantation sera of 504 deceased-donor kidney recipients were tested for IgG HLA class I and class II antibodies, sCD30, and IgA anti-Fab levels using the CTS 4 ELISA kit. Kidney graft survival was estimated by Kaplan-Meier method and multivariate Cox regression. Regardless of the presence of HLA class II antibodies, recipients with high HLA class I reactivity had lower 1-year graft survival than recipients with low reactivity (p < 0.01). Recipients with high sCD30 had lower 5-year graft survival rate than those with low sCD30 (p < 0.01). The sCD30 effect was observed in presensitized and nonsensitized recipients, demonstrated a synergistic effect with HLA class I antibodies (p < 0.001), and appeared to be neutralized in recipients with no HLA class II mismatches. IgA anti-Fab did not influence kidney graft survival. Our results indicate that high pretransplantation sCD30 levels and HLA class I positivity increase the risk of kidney graft loss regardless of other factors. Consequently, such determinations should be routinely performed to estimate recipients' risks of graft rejection before transplantation.

Immunoglobulin isotype-specific characterization of anti-human leukocyte antigen antibodies eluted from explanted renal allografts

To evaluate the immunoglobulin isotypes of anti-human leukocyte antigen (HLA) antibodies harbored in rejected renal allografts, we isolated proteins by acid elution accumulated in 94 rejected and explanted kidneys and characterized their antibody specificities by complement-dependent cytotoxicity, enzyme-linked immunosorbent assay, and flow cytometry (Luminex) techniques. In addition, we differentially analyzed non-complement-binding immunolglobulin (Ig) G2/4 and IgA1/2 antibodies in the eluates using two modified solid phase assays. We found non-complement-binding IgG2 and IgG4 antibodies in 16/58 (28%) of the IgGall-positive eluates, 15 eluates with anti-HLA class I and 4 with anti-HLA class II specificities, respectively. Anti-HLA class I IgG2/4 antibodies directed against the donor were found in 7 eluates (54% of the IgG2/4-pos. eluates), whereas 2 eluates (50%) had class II IgG2/4 antibodies directed against the donor. IgA1/2 antibodies could be detected in 9 eluates (16%); 5 of them had anti-HLA class I and 5 anti-HLA class II antibodies. We could clearly exhibit that explanted kidney allografts harbor anti-HLA antibodies. Moreover, our study demonstrates that non-complement-binding anti-HLA antibodies accumulate in rejected renal allografts.

Immunoglobulin Induction Therapy in Renal Transplant Recipients: Effects on Immunoglobulin and Regulatory Antibody Levels

We have previously shown that high pretransplant regulatory autoantibodies are associated with better kidney graft outcome. To analyze the effect of intravenous immunoglobulin (IVIG) induction therapy on these regulatory antibodies, we performed a prospective randomized study in 50 renal transplant recipients who were randomly assigned to receive 7 x 10 g IVIG or 7 x 10 g IV albumin infusions. Basic immunosuppressive therapy consisted of tacrolimus/azathioprine (n = 24) and tacrolimus/mycophenolate mofetil (n = 26), respectively. ELISA was used to assess IgG-/IgA-anti-Fab, -anti-F(ab)2 and -anti-hinge regulatory antibodies. IVIG induction therapy resulted in upregulation of serum IgG and IgA levels within the first 20 days posttransplant (P = .001, IgG; P = .04, IgA), so that a significant IgG deficiency was found only in non-IVIG patients (day 10: IgG <6 g/L: 7/25 (28%) non-IVIG versus 0/25 IVIG patients; P = .005). As the IVIG charges contained all of the regulatory antibodies tested, intravenous administration of these antibodies explain the elevated IgG- and IgA-anti-F(ab)2 antibody levels found in IVIG compared to non-IVIG patients on day 10 (P = .005 and P = .04, respectively). Our data indicated that IVIG induction prevented severe IgG deficiency in the early posttransplant period but had no impact on severe infectious complications. IVIG induction enhanced immunoregulatory antibody levels early posttransplant, which might provide graft protective effects.

Detection of Anti-MICA Antibodies in Patients Awaiting Kidney Transplantation, during the Post-transplant Course, and in Eluates from Rejected Kidney Allografts by Luminex Flow Cytometry

Previously we have reported on the development of antibodies against MICA alleles in kidney transplant recipients. These alloantibodies have now been determined using a new assay using Luminex beads bound to soluble recombinant MICA antigens produced in insect cells. In the present study we have analyzed sera from 85 kidney transplant recipients on the waiting list and 66 patients transplanted within the last 4 years and 59 acid eluates obtained from allograft nephrectomy specimens. Many of the patients in those groups were sensitized and some had previous transplants (waiting list: 15%; post-tx: 7.6%; eluates 22%) and their sera were found to contain anti-human leukocyte antigen (HLA) and anti-MICA antibodies. Anti-MICA antibodies were detected in 21/85 (24.7%) of the waiting list patients and in 15/66 (22.7%) of the transplanted recipients; 11 of the eluates (18.6%) were found to have MICA-specific antibodies (6 of them also had anti-HLA antibodies and 5 did not). These data suggested that immunization against mismatched MICA alleles induces development of anti-MICA antibodies. The finding of MICA allele-specific antibodies in eluates of kidney transplants suggests that anti-MICA antibodies can be involved in the pathogenesis of kidney allograft rejection. Further studies will be required to determine whether patients who produce alloantibodies against MICA alleles are at risk for transplant rejection even when no HLA antibodies are detected.

IgM antibodies identified by a DTT-ameliorated positive crossmatch do not influence renal graft outcome but the strength of the IgM lymphocytotoxicity is associated with DR phenotype

A positive crossmatch that is rendered negative by treating the serum with the IgM-reducing agent dithiothreitol (DTT) is generally reported not to influence short-term renal graft outcome. Its effect on long-term (> or = 3 years) cadaveric and live-donor transplant function, however, is less clear. We evaluated the effect of IgM antibodies in a DTT-ameliorated positive crossmatch (DTT-APXM) on long-term renal graft outcome in 1,290 consecutive cadaveric renal transplants (8-year survival) and 384 live-donor renal transplants (7-year survival) from patients transplanted between 1990 and 1999. The data show that 1- and 8-year graft survival for cadaveric renal transplants in patients with IgM antibodies (n=72) (DWFG censored = 91% and 65%; DWFG not censored = 90% and 60%) was not significantly different from the group without IgM antibodies (n = 1,218) (DWFG censored = 92% and 71%; DWFG not censored = 87% and 55%) (log-rank = 0.25 for DWFG censored, log-rank = 0.92 for DWFG not censored). The one- and seven-year graft survival for live-donor renal transplants in patients with IgM antibodies seen in a DTT-APXM (n = 22) (DWFG censored = 95% and 83%; DWFG not censored = 95% and 66%) was not significantly different from the group without IgM antibodies (n = 362) (DWFG censored = 94% and 81%; DWFG not censored = 92% and 73%) (log-rank = 0.61 for DWFG censored, log-rank = 0.89 for DWFG not censored). DR phenotype was found to be associated with the strong (>40% cell death) IgM reactivity in both black and white patients. In white patients, DR2 was more frequently seen with a strong IgM crossmatch (48.2%) than in molecularly typed controls (28.5%) (P < 0.03) and concomitant with that DR increase, DR4 was decreased in white patients (6.8%) compared with controls (25.5%) (P < 0.02). In black patients with strong IgM reactivity, DR6 was increased in patients (46.1%) compared with controls (20.5%) (P = 0.07) and concomitant with that DR6 increase, DR5 was decreased in frequency in black patients (7.6%) compared with controls (41%) (P < 0.03). These data show that long-term graft survival in renal transplantation is not negatively influenced by the presence of donor-reactive lymphocytotoxic antibodies in the crossmatch ameliorated by serum DTT treatment. They also suggest that the strength of the IgM antibody response is regulated in part by certain gene (s) of the DR region.