Superior 3-year kidney graft function in patients with impaired pretransplant Th2 responses

Predictive biomarkers of renal allograft failure

BACKGROUND

Survival of renal allografts is limited by chronic allograft deterioration resulting from processes that are difficult to detect in their early stages, when therapeutic interventions would be most effective. Predictive biomarkers from easily accessible specimens, such as blood or urine, might improve early diagnosis of smoldering graft-damaging processes and help with the identification of patients at particularly high risk of sustained injury, thereby helping to tailor therapy and appropriate follow-up screening.

OBJECTIVE

This article reviews recently investigated biomarkers for the prediction of renal allograft failure, outlines the new '-omic' technologies as a potential source for the identification of new predictive biomarkers and judges the practical value of predictive biomarkers at the present timepoint.

METHODS

A literature search was performed using the medical database PubMed. No general restrictions (e.g., year of publication) were applied, but the focus was set on more recently published articles.

CONCLUSION

Despite a large number of interesting studies, none of the investigated candidate biomarkers is robustly established for widespread clinical use or able to replace biopsies for graft assessment.

Prognostic assays for rejection and tolerance in organ transplantation

In this review, I have summarised our understanding of acute rejection of organ transplants, and for convenience I have identified three processes, recognition, rejection and regulation. In stark contrast to this text-book picture of acute rejection, I have drawn attention to some of the clinical realities, where processes are altered by powerful immunosuppressive drugs, and where many transplant recipients are pre-sensitised to transplantation antigens prior to engraftment. The ultimate goal is to encourage the emergence of a utopian immunological state, wherein patients tolerate organ transplants for life after being weaned from all immunosuppressive drugs. Assays that may be used in the future to reliably monitor this process are still at a very exciting stage of development.

Mycophenolate mofetil-based immunosuppression and cytokine genotypes: effects on monokine secretion and antigen presentation in long-term renal transplant recipients

BACKGROUND

It has been suggested that increased monocyte responses might play a role in chronic allograft rejection.

METHODS

We investigated in vitro monokine responses in 112 patients with long-term stable kidney graft function (ST patients; n=80, non-mycophenolate mofetil [MMF]; n=32, MMF) and 25 patients with chronic renal transplant rejection (CR patients; non-MMF). Interleukin 10 and tumor necrosis factor (TNF)-alpha promoter gene polymorphisms were tested by polymerase chain reaction and sequence-specific primers; antigen-presenting capacity (AC) of monocytes was tested by incubation with staphylococcal superantigens (SEA, SEE, SED).

RESULTS

Although non-MMF-based immunosuppression in ST patients did not result in compromised AC or lipopolysaccharide (LPS)-stimulated monokine responses compared with healthy controls, we found MMF therapy to be associated with significantly reduced TNF-R1 expression on monocytes (P<0.001), suppressed AC (P<0.02, SED), and suppressed LPS-stimulated IL-1 beta, IL-10, and TNF-alpha secretion (P<0.01). Coinciding with a significantly higher steroid dosage in CR patients, IL-6 receptor and TNF-R1 expression on monocytes were down-regulated (P< or =0.02) and AC was suppressed in CR compared with ST (non-MMF) patients (P<0.01, SED; P<0.05, SEE). However, LPS-stimulated monokine secretion was not decreased or even enhanced (IL-6, granulocyte-macrophage colony-stimulating factor [GM-CSF]; P<0.05). Enhanced in vitro IL-10 responses (>500 pg/mL) were found predominantly in non-MMF-treated patients with the IL-10 genotype GCC (GCC: 23/62 [37%], non-GCC: 2/27 [7%], P<0.005; GCC and non-MMF: 22/47 [47%], GCC and MMF: 1/15 [7%], P<0.005].

CONCLUSION

Steroids and azathioprine did not sufficiently suppress monokine responses, whereas MMF treatment might inhibit chronic graft rejection because of suppression of TNF-R1 expression and vigorous inhibition of monokine secretion. MMF treatment may especially be indicated in patients with the IL-10 "high-producer" genotype GCC.

Cyclosporine microemulsion- and mycophenolate mofetil-related lymphoid aggregates are not associated with acute rejection

BACKGROUND

Microemulsion cyclosporine, mycophenolate mofetil, and prednisone have become a common immunosuppressive protocol in renal transplantation. We identified lymphocytic infiltrates in transplant fine-needle aspirates and core biopsies from patients on this regimen without acute rejection clinically or by standardized morphological criteria and investigated this inflammatory response.

METHODS

Twenty-eight aspirates from 21 patients were included and assessed in the standard fashion. Nine core biopsies showing interstitial lymphocytic infiltration were evaluated with antibodies against CD3, CD4, CD8, CD20, CD30, CD56, KP1, and epithelial membrane antigen (EMA). Aspirates and biopsies were assessed for tubular cell major histocompatibility complex (MHC) class II antigen and for gamma-interferon (gamma-IFN), interleukin-4 (IL-4), and IL-10 mRNAs by reverse transcription-polymerase chain reaction.

RESULTS

Fifteen aspirates showed immune activation solely due to mature lymphocytes and monocytes; 13 had no immune activation. All aspirates were negative for MHC class II antigens. Of 6 activated aspirates assessed for gamma-IFN mRNA, 5 were negative. All 21 patients had similar clinical characteristics and recovered renal function without rejection treatment. The core biopsies had lymphocytes in 5-30% of the interstitium. The cells were 70-85% CD3+, with 50-85% CD4+, 3-10% KP1+, and rare cells CD56+. No T-cell activation was present (EMA- and CD30-). Seven biopsies were assessed and were negative for gamma-IFN mRNA; only one biopsy had weakly positive MHC class II staining. Two activated aspirates were negative for IL-4 and IL-10 mRNA, while three biopsies each contained IL-4 and IL-10 mRNAs.

CONCLUSIONS

Inactive interstitial lymphoid infiltrates are frequent in patients on this drug regimen and should not be interpreted as acute rejection, particularly in aspirate samples. These lymphocytes may play a role in long-term allograft acceptance.

Switch from cyclosporine A to tacrolimus in renal transplant recipients: impact on Th1, Th2, and monokine responses

We showed previously that pretransplant CD4 helper defects and low in-vitro IL-10 responses predict a low risk of acute kidney graft rejection. To compare the effect of tacrolimus (Tacr) and cyclosporine A (CsA) on the humoral immune response we assessed T helper function, B cell/monocyte responses and in-vitro cytokine responses (TNF-alpha, GM-CSF, IL-1 beta, IL-2, IL-4, IL-6, IL-10) in 20 renal transplant recipients before and 3 months after they were switched from CsA to Tacr because of hyperlipoproteinemia, hirsutism, or gum hyperplasia. T helper function was assessed using a PWM-driven allogeneic coculture system of patient T cells together with control B cells. B cell/monocyte responses were determined using a PWM-stimulated allogeneic coculture system, SAC I-stimulated B-cell cultures and LPS-stimulated monocyte cultures. Immunoglobulin-secreting cell (ISC) responses were assessed in a reverse hemolytic plaque assay, and ELISA were used to determine cytokine secretion. Treatment with Tacr resulted in a decreased expression of costimulatory ligands and adhesion molecules (T cells: CD40L, p < 0.05; CD28 and CD54, p < or = 0.01; B cells: CD25, p = 0.05; CD40, p < 0.001; monocytes: CD40, p < 0.05), which coincided with decreased PHA-stimulated T cell IL-2 responses (398 +/- 153 versus 43 +/- 15 pg/ml, p < 0.05), impaired CD4 helper activity (117% +/- 22% versus 73% +/- 19%, p < 0.05) and increased CD4 suppressor activity (-120% +/- 28% versus -18% +/- 27%, p = 0.02). We observed enhanced CD4 IL-10 responses (p < 0.01) and LPS-stimulated monocyte responses (TNF-alpha, IL-1 beta, and IL-6, p < 0.005; IL-10, p < 0.05), indicating an increased humoral immune responsiveness under treatment with tacrolimus. Our data show that switching of immunosuppressive therapy from CsA to tacrolimus results in suppression of costimulatory ligands, adhesion molecules, Th1 responses and CD4 helper activity. However, enhanced humoral immune responses, Th2 and monokine responses, might have a negative impact on long-term graft function.