The immunological monitoring of kidney and liver transplants in adult and pediatric recipients

Advances in Rejection Management: Prevention and Treatment

Extended survival of liver transplant recipients has brought rejection management to the forefront of liver transplant research. This article discusses T-cell-mediated rejection, antibody-mediated rejection, and chronic rejection. We focus on the prevention and then discuss treatment options. Future directions of rejection management include biomarkers of rejection, which may allow for monitoring of patients who are considered high risk for rejection and detection of rejection before there is any clinical evidence to improve graft and patient survival. With improved graft life and survival of liver transplant recipients, the new frontier of rejection management focuses on immunosuppression minimization, withdrawal, and personalization.

Clinical use of an immune monitoring panel in liver transplant recipients: A prospective, observational study

Immunosuppressive therapy greatly contributed to making liver transplantation the standard treatment for end-stage liver diseases. However, it remains difficult to predict and measure the efficacy of pharmacological immunosuppression. Therefore, we used a panel of standardized, commonly available, biomarkers with the aim to describe their changes in the first 3 weeks after the transplant procedure and assess if they may help therapeutic drug monitoring in better tailoring the dose of the immunosuppressive drugs. We prospectively studied 72 consecutive patients from the day of liver transplant (post-operative day #0) until the post-operative day #21. Leukocytes, neutrophils, lymphocytes (CD4+, CD8+), natural killer cells, monocytes, immunoglobulins and tacrolimus serum levels were measured on peripheral blood (at day 0, 3, 7, 14, 21 after surgery). Patients who developed infections showed significantly higher CD64+ monocytes on post operative day #7. IgG levels were lower on post operative day #3 among patients who later developed infections. We also found that a sharp decrease in IgA from post operative day #0 to 3 (-226 mg/dL in the ROC curve analysis) strongly correlates with the onset of infections among HCV- patients. No specific markers of rejection emerged from the tested panel of markers. Our results show that some early changes in peripheral blood white cells and immunoglobulins may predict the onset of infections and may be useful in modulating the immunosuppressive therapy. However, a panel of commonly available, standardized biomarkers do not support in improving therapeutic drug monitoring ability to individualize immunosuppressive drugs dosing.

Immune monitoring as prerequisite for transplantation tolerance trials

Ever since its first application in clinical medicine, scientists have been urged to induce tolerance towards foreign allogeneic transplants and thus avoid rejection by the recipient's immune system. This would circumvent chronic use of immunosuppressive drugs (IS) and thus avoid development of IS-induced side effects, which are contributing to the still unsatisfactory long-term graft and patient survival after solid organ transplantation. Although manifold strategies of tolerance induction have been described in preclinical models, only three therapeutic approaches have been utilized successfully in a still small number of patients. These approaches are based on (i) IS withdrawal in spontaneous operational tolerant (SOT) patients, (ii) induction of a mixed chimerism and (iii) adoptive transfer of regulatory cells. Results of clinical trials utilizing these approaches show that tolerance induction does not work in all patients. Thus, there is a need for reliable biomarkers, which can be used for patient selection and post-therapeutic immune monitoring of safety, success and failure. In this review, we summarize recent achievements in the identification and validation of such immunological assays and biomarkers, focusing mainly on kidney and liver transplantation. From the published findings so far, it has become clear that indicative biomarkers may vary between different therapeutic approaches applied and organs transplanted. Also, patient numbers studied so far are very small. This is the main reason why nearly all described parameters lack validation and reproducibility testing in large clinical trials, and are therefore not yet suitable for clinical practice.

Application and interpretation of histocompatibility data in pediatric kidney transplantation

PURPOSE OF REVIEW

Advances in technology to assess immunologic risk in solid organ transplant offer an opportunity to optimize the approach to pediatric deceased donor kidney transplant in the setting of a new allocation system in the United States.

RECENT FINDINGS

Degree of human leukocyte antigen (HLA) mismatch, class II HLA mismatch, unacceptable antigens and donor-specific antibody (DSA) detected by solid-phase assays, and epitope matching pretransplant affect pediatric kidney transplant outcomes. Detection of de novo DSAs (dnDSAs) posttransplant has been associated with increased risk of acute rejection and worse allograft function. Development of dnDSA occurs in recipients with greater epitope mismatching.

SUMMARY

Improved long-term outcomes may be anticipated in pediatric kidney transplant recipients by incorporating extended HLA mismatch information and updating the clinical approach to donor kidney matching using available technology to identify clinically relevant immunologic risk.

High-dose immunosuppressant alters the immunological status of New Zealand white rabbits following skin transplantation

The aim of this study was to investigate the effect of an immunosuppressant on the immunological status of New Zealand white rabbits after skin grafting, and to evaluate a method for monitoring the immunological status of subjects with skin transplants. The rabbits were randomly divided into allograft rejection, autograft tolerance, nontransplant, allograft low-dose immunosuppressant and allograft high-dose immunosuppressant groups. The rabbits in the low- and high-dose immunosuppressant groups were treated with cyclosporine A intravenously 8 h prior to skin transplantation and once daily following transplantation at doses of 2 and 25 mg/kg, respectively. At 12 days after skin transplantation, the spleens of donor (female) rabbits and recipient (male) rabbits were harvested for the preparation of single-cell suspensions. The splenocytes from recipient and donor rabbits were labeled with 0.3 or 6 µM carboxy fluorescein diacetate succinimidyl ester, respectively, and a mixed cell suspension was prepared. The final preparation was intravenously injected into recipient New Zealand white rabbits. The ratio of the two fluorescently labeled cell populations in the peripheral blood was measured using flow cytometry at 1, 2, 4 and 8 h after the injection, and the cell death rate was calculated. Histological analysis was also performed on samples collected at the time of splenectomy. The cell death rates of the allograft rejection and low-dose immunosuppressant groups reached their highest levels 8 h after the injection of spleen cell suspension. Allogeneic spleen cells from donor male rabbits were almost completely removed within 8 h of injection. The cell death rate increased slowly in the nontransplant, autograft and high-dose immunosuppressant groups without specificity. This study provides a specific method for the in vivo monitoring of the immunological status of patients after skin grafting. This method can quickly and accurately detect the immunological status of recipients following the injection of a mixed splenocyte suspension, thereby indicating the strength of immune rejection by the immune systems of the recipients.

Pre-transplant donor-specific Interferon-gamma-producing cells and acute rejection of the kidney allograft

BACKGROUND

Our retrospective study included a cohort of 47 patients who underwent living donor kidney transplantation.The pre-transplant frequencies of donor-specific Interferon-gamma (IFN-γ) producing cells were define dusing enzyme-linked immunosorbent spot (ELISpot) assay and correlated with incidence of acute cellular(ACR), antibody-mediated rejection (AMR) and kidney graft survival up to one year after transplantation.

RESULTS

We found a statistically significant correlation between the frequencies of IFN-γ-producing cells and the number of mismatches in HLA antigens between patients and their respective donors – for Class I – A and B (r = 0.399, p b 0.01) and for Class I and Class II antigens – A, B and DR (r = 0.409, p b 0.01). No significant relationship was observed between the numbers of IFN-γ-secreting cells and incidence of acute rejection (neither ACR, nor AMR). However, there was a trend of elevated frequencies of IFN-γ-producing cells in patients who developed ACR or AMR in comparison with kidney recipients free of rejection (91 ± 82 and 114 ± 75 vs. 72 ± 70/5 × 10(4) peripheral blood mononuclear cells respectively). Patients with concurrent acute cellular and antibody-mediated rejection had also higher numbers of IFN-γ-producing memory/effector cells compared to patients with cellular rejection only.

CONCLUSION

Pre-transplant determination of the numbers of IFN-γ-producing donor-specific memory cells using the ELISpot technique may provide clinically relevant results when evaluating the risk of development of acute cellular and antibody-mediated rejection. These frequencies are influenced by the degree of HLA mismatching between patients and their respective kidney donors.

Immune monitoring post liver transplant

Many of the causes of short and late morbidity following liver transplantation are associated with immunosuppression or immunosuppressive medications. Current care often involves close monitoring of liver biochemistry as well as therapeutic drug levels. However, the postoperative course following liver transplantation can often be associated with significant complications including infection and rejection, suggesting an inadequacy in current immune function monitoring. Many assays have been tested in the research setting to identify possible biomarkers that may be used to predict clinical events such as acute cellular rejection, and therefore allow modification of a patient’s immunosuppressive regimen prior to a clinical event. However, these generally require significant laboratory processing and have had difficulty becoming established in common clinical use outside the research setting. One assay, Cylex ImmuKnow has been food and drug administration approved but has had variable results. In this review we discuss the assays that have been used to assess monitoring of immune function after liver transplantation and consider possible future directions.

Peripheral blood biomarkers for the characterization of alloimmune reactivity after pediatric liver transplantation

Individualization of immunosuppressive medications is an important objective in transplantation medicine. Reliable biomarkers to distinguish between patients dependent from intensive immunosuppressive therapy and those where therapy can be minimized among pediatric transplant recipients receiving immunosuppressive medications are still not established. We evaluated the potential of cross-sectional quantification of regulatory T cells, lymphocyte subsets, and cytokine concentrations as biomarkers in 60 pediatric liver transplant recipients with AR, CR, or normal graft function and in 11 non-transplanted patients. Transplant recipients presenting with AR had significantly higher CD8+ T-cell counts, significantly higher concentrations of IL-2, and increased levels of IFN-γ compared with asymptomatic patients or controls. Regulatory T-cell numbers did not differ between children with rejection and children with good graft function. A tendency toward increased concentrations of IL-4 and TGF-β was detected in transplant recipients with good graft function. Cross-sectional parameters of peripheral regulatory T cells in pediatric liver transplant recipients do not seem to be valuable biomarkers for individualizing immunosuppressive therapy prior to the weaning process. Lymphocyte subsets, IL-2, IFN-γ, IL-4, and TGF-β serum concentrations may be helpful to identify children in whom immunosuppression can be reduced or discontinued.

King's College Hospital Criteria for non-acetaminophen induced acute liver failure in an international cohort of children

OBJECTIVE

To validate King's College Hospital criteria (KCHC) in children with non-acetaminophen induced pediatric acute liver failure (PALF) and to determine whether re-optimizing the KCHC would improve predictive accuracy.

STUDY DESIGN

We used the PALF study group database. Primary outcomes were survival without liver transplantation vs death at 21 days following enrollment. Classification and regression tree analysis was used to determine if modification of KCHC parameters would improve classification of death vs survival.

RESULTS

Among 163 patients who met KCHC, 54 patients (33.1%) died within 21 days. Sensitivity of KCHC in this cohort was significantly lower than in the original study (61% vs 91%, P = .002), and specificity did not differ significantly. The positive predictive value (PPV) and negative predictive value (NPV) of KCHC for this cohort was 33% and 88% respectively. Classification and regression tree analysis yielded the following optimized parameters to predict death: grade 2-4 encephalopathy, international normalized ratio >4.02, and total bilirubin >2.02 mg/dL. These parameters did not improve PPV, but NPV was significantly better (88% vs 92%, P < .0001).

CONCLUSIONS

KCHC does not reliably predict death in PALF. With a PPV of 33%, twice as many participants who met KCHC recovered spontaneously than died, indicating that using KCHC may cause over utilization of liver transplantation. Re-optimized cutpoints for KCHC parameters improved NPV, but not PPV. Parameters beyond the KCHC should be evaluated to create a predictive model for PALF.

Prope tolerance after pediatric liver transplantation

pT, under mono- and infratherapeutic calcineurin inhibition, may constitute an optimal condition combining graft acceptance with low IS load and minimal IS-related toxicity. We reviewed 171 pediatric (<15.0 yr) survivors beyond one yr after LT, transplanted between April 1999 and June 2007 under tacrolimus-based regimens (median follow-up post-LT: 6.0 yr, range: 0.8-9.5 yr). Their current status regarding IS therapy was analyzed and correlated with initial immunoprophylaxis. pT was defined as tacrolimus monotherapy, with mean trough blood levels <4 ng/mL during the preceding year of follow-up, combined with normal liver function tests. The 66 children transplanted before April 2001 received a standard tacrolimus-steroid regimen. Beyond April 2001, 105 patients received steroid-free tacrolimus-basiliximab or tacrolimus-daclizumab immunoprophylaxis. In the latter group, 43 (41%) never experienced any acute rejection episode and never received steroids. In the long term, a total of 79 recipients (47%) developed pT (n = 73) or IS-free operational tolerance (n = 6), 27 of them belonging to the 43 steroid-free patients (63%). In contrast, only 52/128 (41%) children treated with steroids subsequently developed prope/operational tolerance (p = 0.012). Steroid-free tacrolimus-based IS seems to promote long-term graft acceptance under minimal/no IS. These results constitute the first evidence that minimization of IS, including steroid avoidance, might be tolerogenic in the long term after pediatric LT.