T-cell function monitoring in stable renal transplant patients treated with sirolimus monotherapy

A high concentration of TGF-β correlates with opportunistic infection in liver and kidney transplantation

Transforming growth factor-β (TGF-β) has been associated with numerous human infections, but its role in the occurrence of opportunistic infection (OI) after solid organ transplantation remains unexplored. This study aimed to assess the utility of the TGF-β following in vitro stimulation of whole peripheral blood (WPB) as a surrogate biomarker of post-transplant OI in a cohort of liver and kidney recipients. Thirty liver and thirty-one kidney transplant recipients were recruited to be prospectively monitored for one-year post-transplantation. Enzyme-linked immunosorbent assay (ELISA) was performed to calculate IFN-γ, IL-17, IL-10 and TGF-β concentration in the supernatant from the activated WPB. Recipients showed higher TGF-β concentrations compared to IFN-γ, IL-17, IL-10 at baseline, although these differences were not significant between INF and NoINF. However, recipients who developed an OI within the first sixth months had a higher concentration of TGF-β than those without OI. A concentration of TGF-β > 363.25 pg/ml in liver and TGF-β > 808.51 pg/ml in kidney recipients were able to stratify patients at high risk of OI with a sensitivity and specificity above 70% in both types of solid organ transplantations. TGF-β could provide valuable information for the management of liver and kidney recipients at risk of post-transplant infection.

Immunosuppressive Agents and Infectious Risk in Transplantation: Managing the "Net State of Immunosuppression"

Successful solid organ transplantation reflects meticulous attention to the details of immunosuppression, balancing risks for graft rejection against risks for infection. The 'net state of immune suppression' is a conceptual framework of all factors contributing to infectious risk. Assays which measure immune function in the immunosuppressed transplant recipient relative to infectious risk and allograft function are lacking. The best measures of integrated immune function may be quantitative viral loads to assess the individual's ability to control latent viral infections. Few studies address adjustment of immunosuppression during active infections. Thus, confronted with infection in solid organ recipients, the management of immunosuppression is based largely on clinical experience. This review examines known measures of immune function and the immunologic effects of common immunosuppressive drugs and available studies reporting modification of drug regimens for specific infections. These data provide a conceptual framework for the management of immunosuppression during infection in organ recipients.

Prediction of Free from Total Mycophenolic Acid Concentrations in Stable Renal Transplant Patients: A Population-Based Approach

BACKGROUND

A population pharmacokinetic (PK) protein-binding model was developed to (1) predict free mycophenolic acid (fMPA) based on total MPA (tMPA) concentrations in renal transplant patients, to establish the therapeutic range of fMPA through pharmacokinetic-pharmacodynamic studies; and (2) provide a guideline for dosing mycophenolate mofetil (MMF).

METHODS

Full PK profiles of 56 patients (from five different occasions) during the first year after transplantation who were treated with oral MMF and cyclosporine, or macrolides (either tacrolimus or sirolimus), were analysed. fMPA protein-binding was modelled using nonlinear mixed effects modelling (NONMEM). The influence of physiological factors and coadministered immunosupressant was studied.

RESULTS

A two-compartment model with first-order absorption and elimination, linear protein binding and enterohepatic circulation (EHC) best described the PK of MPA. Different recycling rate constants were considered depending on the coadministered immunosuppressant. The protein-binding rate constant (K_B [relative standard error, RSE%]) increased nonlinearly with renal function according to K _B = 43.1 (3.13)·(CL_CR/59.51)^0.394(10.66) h^-1. Furthermore, fMPA plasma clearance, given by clearance of the free mycophenolic acid (CL_fMPA), CL_fMPA = 410 (RSE%3.00)·(1+CsA·0.594 (22.39)) L/h, was 59.4% greater in cyclosporine-treated patients than in macrolide-treated patients, leading to lower MPA exposures. External evaluation proved acceptable area under the plasma concentration-time curve and trough concentration predictions.

CONCLUSIONS

A reliable protein-binding population PK model was developed for prediction of fMPA or tMPA from each other and for dose guiding in stable renal transplant recipients.

Low T-Cell Responses to Mitogen Stimulation Predicts Poor Survival in Recipients of Allogeneic Hematopoietic Stem Cell Transplantation

Background

Successful engraftment and reconstitution of the innate and adaptive immune system are associated with improved outcomes in recipients of allogeneic hematopoietic stem cell transplantation (HSCT). A clinically meaningful and simple biomarker of immunosuppression could potentially assist clinicians in their decision-making. We aimed to determine the relationship between T-cell production of interferon gamma (IFN-γ) in response to phytohemagglutinin (PHA) to clinical outcomes in HSCT recipients.

Methods

A prospective observational multicenter study of 73 adult allogeneic HSCT recipients was conducted in Melbourne, Australia. Eligible participants were >18 years and at risk of cytomegalovirus disease. T-cell responses to PHA were assessed at 3, 6, 9, and 12 months post-HSCT using the commercial quantiferon-cytomegalovirus assay, which quantifies IFN-γ production by ELISA following stimulation with PHA. A low response was defined as IFN-γ <0.5 IU/ml following stimulation with PHA.

Results

At 3 months post-HSCT, high responses to PHA (median IFN-γ 7.68 IU/ml) were seen in 63% of participants and low responses to PHA (median IFN-γ 0.06 IU/ml) in 37%. IFN-γ responses to PHA were significantly associated with the severity of acute graft versus host disease (AGVHD) (spearman r = −0.53, p < 0.001) and correlated with blood lymphocyte count (spearman r = 0.52, p < 0.001). Twelve month overall survival was greater in individuals with high compared to low IFN-γ response to PHA at 3 months [92 vs. 62%, respectively, Cox proportional hazard ratio (HR): 4.12 95% CI: 1.2–13.7, p = 0.02]. Non-relapse mortality (NRM) was higher in individuals with low IFN-γ response to PHA (competing risk regression HR 11.6 p = 0.02). In individuals with no AGVHD compared to AGVHD and high IFN-γ response to PHA compared to AGVHD and low IFN-γ response to PHA, 12-month survival was 100 vs. 80 vs. 52%, respectively (log rank test p < 0.0001).

Conclusion

Low IFN-γ response to PHA at the 3-month time-point following allogeneic HSCT was predictive of reduced 12-month overall survival, increased NRM, and reduced survival in recipients with AGVHD. Assessing IFN-γ response to PHA post-HSCT may be a clinically useful immune biomarker.

Clinical implementation of pharmacogenetics

In the last decade, pharmacogenetic research has been performed in different fields. However, the application of pharmacogenetic findings to clinical practice has not been as fast as desirable. The current situation of clinical implementation of pharmacogenetics is discussed. This review focuses on the advances of pharmacogenomics to individualize cancer treatments, the relationship between pharmacogenetics and pharmacodynamics in the clinical course of transplant patients receiving a combination of immunosuppressive therapy, the needs and barriers facing pharmacogenetic clinical application, and the situation of pharmacogenetic testing in Spain. It is based on lectures presented by speakers of the Clinical Implementation of Pharmacogenetics Symposium at the VII Conference of the Spanish Pharmacogenetics and Pharmacogenomics Society, held in April 20, 2015.

Pharmacodynamics of T cell function for monitoring pharmacologic immunosuppression after allogeneic hematopoietic stem cell transplantation

Information on pharmacodynamic monitoring after allogeneic hematopoietic cell transplantation (allo-SCT) to evaluate individual responses to immunosuppressive drugs is scarce. We studied the relationship between a panel of pharmacodynamic markers monitored during the first 3 months after transplant and the occurrence of graft-versus-host disease (GVHD). Lymphocyte activation assessed by intracellular ATP concentration in CD4⁺ T cells, a high percentage of CD8⁺ effector T cells, and a low percentage of CD4⁺ regulatory T (Treg) cells correlated significantly with GVHD. A cutoff value of 0.5 for the CD8⁺ effector T/Treg ratio provided the most accurate diagnosis of GVHD (sensitivity 58.8%, specificity 91%). These pharmacodynamic markers may provide an efficient complement to standard pharmacokinetic monitoring of immunosuppressive drugs after allo-SCT.

Comparison of several functional methods to evaluate the immune response on stable kidney transplant patients

The introduction of new immunosuppressive drugs in the last two decades has been associated with a significant decline in the prevalence of acute rejection and a huge improvement of graft survival. Monitoring blood levels of immunosuppressive drugs is the most common way to control drug doses in renal transplant patients. This approach is useful and widely used but doesn't give accurate information about the immune status of the patient. For this goal, there are many "in house" protocols which give more information, but cannot be standardized, limiting their applicability to compare results between different laboratories. In this study we compare three classical functional methods to evaluate the immune response: Mixed lymphocyte reaction (MLR), phytohemagglutinin stimulated peripheral blood lymphocytes (PBLs), and anti-CD3 monoclonal antibodies (mAbs) against PBL with the only FDA-labeled assay to measure the patient immune status: Cylex ImmuKnow® that measures the intracelullar ATP in CD4+ lymphocytes. We used n=111 stable renal transplant patients, all the patients with more than one year functioning grafts. We referred the results to a control population of healthy blood donors (n=125).

RESULTS

Measurement of intracellular ATP in CD4+ lymphocytes is able to differentiate immunosuppressed populations in renal transplant patients from health controls (242.30±21.62 vs. 386.43±25.12, p 0.0001). By contrary, there were no differences between controls and renal recipients when functional response was measured by MLR, PHA and anti-CD3 mAbs (2.48±0.45 vs. 2.37±0.41; 2.84±0.76 vs. 2.37±0.32; 2.32±0.34 vs. 1.89±0.38 respectively). In summary, our results show that the measurement of ATP in CD4+ lymphocytes gives more accurate information in comparison to the classical methods.

Intracellular IFN-γ and IL-2 expression monitoring as surrogate markers of the risk of acute rejection and personal drug response in de novo liver transplant recipients

Biomarker monitoring is needed in transplantation to reflect individual response to immunosuppressive drugs and graft outcome. We evaluated intracellular expression and soluble production of interferon-(IFN)-γ and interleukin-(IL)-2 as predictive biomarkers of acute rejection (AR) and personal drug response. Pharmacokinetic-pharmacodynamic profiles were determined in 47 de novo liver recipients treated with tacrolimus, mycophenolate mofetil and prednisone. Of the 47 patients, AR occurred in nine. There were no differences in drug concentrations between rejectors and non-rejectors. A pre-transplantation cut-off value of 55.80% for %CD8(+)-IFN-γ(+) identified patients at high risk of AR with a sensitivity of 75% and a specificity of 82%. In the first week post-transplantation, patients with a % inhibition for soluble IFN-γ, %CD8(+)-IFN-γ(+) and %CD8(+)-IL2(+) lower than 40% developed AR, showing low susceptibility to immunosuppressive drugs. Therefore, effector-T-cell response monitoring may help physicians to identify personal response to treatment and patients at high risk of AR.

Biomarker assessment of the immunomodulator effect of atorvastatin in stable renal transplant recipients and hypercholesterolemic patients

BACKGROUND

HMG-CoA reductase inhibitors (statins) have effects beyond lipid lowering, including immunomodulatory and anti-inflammatory properties. Statins are frequently combined with immunosuppressive agents in transplant recipients to modulate the hyperlipidemic side effects of the immunosuppressants. However, the role of statins in the immunosuppressive response that is achieved in individual patients remains to be assessed.

OBJECTIVE

The aim of this study was to evaluate the immunomodulatory effect of atorvastatin given alone and in combined treatment with tacrolimus and mycophenolate mofetil.

STUDY DESIGN

Two patient groups were studied: renal transplant recipients receiving tacrolimus and mycophenolate mofetil therapy, and hypercholesterolemic patients (the control group). Fasting blood samples were taken from participants before and 1 month after atorvastatin treatment was started to study a small battery of biomarkers that are able to reflect the range of the effects of immunosuppressive therapy and atorvastatin.

SETTING

All patients in the study were enrolled at the Hospital Clinic of Barcelona.

PATIENTS

All patients enrolled in the study were candidates for treatment with atorvastatin because of high cholesterol levels. One group consisted of 25 stable renal transplant recipients with low-density lipoprotein (LDL) cholesterol levels above 100 mg/dL after 3 months of therapeutic lifestyle changes, according to the guidelines of the National Kidney Foundation - Kidney Disease Outcomes Quality Initiative. The other group included 25 hypercholesterolemic patients with LDL cholesterol levels above target values for the patients' overall risk, as derived from the National Cholesterol Education Program Adult Treatment Panel III criteria.

INTERVENTION

Atorvastatin (Lipitor®) treatment was started at a fixed dose of 20 mg daily.

MAIN OUTCOME MEASURE

The studied biomarkers were lymphocyte proliferation, intracellular adenosine triphosphate (ATP) synthesis in CD4+ T cells, intralymphocytary cytokine expression (interleukin [IL]-2, interferon [IFN]-γ), soluble cytokine production (IL-2, IFN-γ, IL-10, IL-17, and transforming growth factor-β) and regulatory T (T(reg)) cells.

RESULTS

Atorvastatin proved to be an immunomodulatory agent, significantly decreasing lymphocyte proliferation by 15% (p = 0.001), increasing ATP levels by 16% (p = 0.0004), and showing a trend toward increasing T(reg) cells in hypercholesterolemic patients (p = 0.09). In the renal transplant recipients, atorvastatin therapy did not modify any of the biomarkers of immunosuppression that were studied.

CONCLUSION

Atorvastatin showed immunoregulatory effects on T cells in hypercholesterolemic patients. These effects were absent in renal transplant recipients, suggesting that the beneficial effects of atorvastatin in this patient group do not relate to immunoregulation. Therefore, statin treatment cannot be considered as a means to reduce the dose of immunosuppressive agents.

Biomarker assessment of the immunomodulator effect of atorvastatin in stable renal transplant recipients and hypercholesterolemic patients

BACKGROUND

HMG-CoA reductase inhibitors (statins) have effects beyond lipid lowering, including immunomodulatory and anti-inflammatory properties. Statins are frequently combined with immunosuppressive agents in transplant recipients to modulate the hyperlipidemic side effects of the immunosuppressants. However, the role of statins in the immunosuppressive response that is achieved in individual patients remains to be assessed.

OBJECTIVE

The aim of this study was to evaluate the immunomodulatory effect of atorvastatin given alone and in combined treatment with tacrolimus and mycophenolate mofetil.

STUDY DESIGN

Two patient groups were studied: renal transplant recipients receiving tacrolimus and mycophenolate mofetil therapy, and hypercholesterolemic patients (the control group). Fasting blood samples were taken from participants before and 1 month after atorvastatin treatment was started to study a small battery of biomarkers that are able to reflect the range of the effects of immunosuppressive therapy and atorvastatin.

SETTING

All patients in the study were enrolled at the Hospital Clinic of Barcelona.

PATIENTS

All patients enrolled in the study were candidates for treatment with atorvastatin because of high cholesterol levels. One group consisted of 25 stable renal transplant recipients with low-density lipoprotein (LDL) cholesterol levels above 100 mg/dL after 3 months of therapeutic lifestyle changes, according to the guidelines of the National Kidney Foundation - Kidney Disease Outcomes Quality Initiative. The other group included 25 hypercholesterolemic patients with LDL cholesterol levels above target values for the patients' overall risk, as derived from the National Cholesterol Education Program Adult Treatment Panel III criteria.

INTERVENTION

Atorvastatin (Lipitor®) treatment was started at a fixed dose of 20 mg daily.

MAIN OUTCOME MEASURE

The studied biomarkers were lymphocyte proliferation, intracellular adenosine triphosphate (ATP) synthesis in CD4+ T cells, intralymphocytary cytokine expression (interleukin [IL]-2, interferon [IFN]-γ), soluble cytokine production (IL-2, IFN-γ, IL-10, IL-17, and transforming growth factor-β) and regulatory T (T(reg)) cells.

RESULTS

Atorvastatin proved to be an immunomodulatory agent, significantly decreasing lymphocyte proliferation by 15% (p = 0.001), increasing ATP levels by 16% (p = 0.0004), and showing a trend toward increasing T(reg) cells in hypercholesterolemic patients (p = 0.09). In the renal transplant recipients, atorvastatin therapy did not modify any of the biomarkers of immunosuppression that were studied.

CONCLUSION

Atorvastatin showed immunoregulatory effects on T cells in hypercholesterolemic patients. These effects were absent in renal transplant recipients, suggesting that the beneficial effects of atorvastatin in this patient group do not relate to immunoregulation. Therefore, statin treatment cannot be considered as a means to reduce the dose of immunosuppressive agents.

In Vitro Studies of the Immunomodulatory Effects of Statins Alone and in Combination with Immunosuppressive Drugs

The effects of statins go beyond their lipid-lowering properties and include immunomodulatory and anti-inflammatory effects. Unfortunately, there is a lack of in vitro assays that study the immunomodulatory effect of statins at therapeutic concentrations and the possible synergism with immunosuppressive drugs. Besides, they are mostly evaluated on isolated peripheral blood mononuclear cells instead of using whole blood as a matrix. The aim of this study is to perform in vitro experiments to evaluate the effect of atorvastatin, simvastatin and fluvastatin at therapeutic concentrations alone and in combination with everolimus or tacrolimus on immunosuppressive response, using whole blood as a matrix by investigating lymphocyte proliferation and production of the soluble cytokines interleukin (IL)-2, IL-10 and interferon (IFN)-γ. Statins (0.1 μM) inhibited T cell proliferation by 12–16% in a dose-dependent manner and when statins at 0.1 μM were combined with each immunosuppressive drug at 8 ng/ml, inhibition increased by 6–9% (p<0.05) for everolimus and 8–15% (p<0.05) for tacrolimus, but not for atorvastatin. At a dose of 0.1 μM, all three statins inhibited soluble IFN-γ production by approximately 5–9% (p<0.02). IL-2 and IL-10 production were unaltered by the presence of statins. These findings suggest that statins seem to exert a mild anti-inflammatory effect that might potentially be used to treat autoimmune diseases.

Target enzyme activity as a biomarker for immunosuppression

Pharmacokinetic drug monitoring has been used for many years to relate immunosuppressant dose to drug exposure in vivo. However, this conventional therapeutic drug monitoring of blood immunosuppressant levels may not necessarily predict the pharmacologic effects on immune cells. The direct determination of target enzyme activity (eg, calcineurin activity, inosine-5'-monophospahte dehydrogenase [IMPDH] activity, p70S6 kinase) may help to better assess the individual response to the immunosuppressant. However, its use is limited by the difficulties of the assay systems, which did not allow yet the prospective assessment of these enzymes in larger patient cohorts with the establishment of validated pharmacodynamic drug monitoring. The most progress regarding a robust and reproducible test system has been achieved with the determination of IMPDH activity as a specific pharmacodynamic parameter of mycophenolic acid activity. This recently validated and standardized assay allows the investigation of IMPDH activity in larger clinical studies. Although the determination of target enzyme activity, eg, by the determination of IMPDH activity, holds promise for a more individualized therapy in transplant medicine, more studies are needed to prospectively validate this approach.

Biomarkers of immunoregulatory status in stable liver transplant recipients undergoing weaning of immunosuppressive therapy

Biomarkers that reflect immune response recovery and predict clinical events during withdrawal or minimization of immunosuppressive therapy have not been evaluated. This study aimed to evaluate whether immune response recovers after withdrawal of long-term immunosuppressive treatment in stable liver transplant patients and to determine whether specific biomarkers reflect immune response reactivity and predict rejection. Pharmacokinetic-pharmacodynamic profiles were determined in 24 patients and 80 healthy donors before immunosuppressive treatment reduction began, at 50%, and at complete withdrawal. In patients who rejected, effector-T-cell response mediated by soluble IFN-γ, %CD4(+)IFN-γ and %CD8(+)IL-2/IFN-γ were significantly increased, while TGF-β1 production and the TGF-β1/IFN-γ ratio were significantly decreased. In patients with rejection, soluble IFN-γ and %CD8(+)IL-2 were significantly higher before immunosuppressive treatment was reduced. Further studies are required, but this battery of biomarkers performed in whole blood could be a useful tool to monitor immunosuppressive treatment minimization or withdrawal protocols and identify patients at increased risk of rejection.

Is the intracellular ATP concentration of CD4+ T-Cells a predictive biomarker of immune status in stable transplant recipients?

BACKGROUND

Intracellular ATP (iATP) production in CD4(+)-T cells has been proposed as a biomarker for routine personalized monitoring in transplant recipients. The aim of our study was to measure this biomarker in adult renal and liver transplant recipients receiving moderate immunosuppressive treatment (IST) during the maintenance period and to evaluate whether this biomarker can effectively predict clinical status (stability, rejection, or infection) and drug effect.

METHODS

iATP concentration and trough blood levels of IST were evaluated in 84 adult transplant recipients (50 renal and 34 liver) during the maintenance period. One hundred and fifty healthy donors were also recruited as a control group. In addition, 22 of 34 liver transplant recipients were included in a clinical study in which IST was withdrawn gradually until total elimination.

RESULTS

Most of the patients evaluated had iATP levels in the moderate immune response zone during a posttransplantation maintenance period with no relevant clinical events. iATP levels were significantly lower in transplant patients with infection (n=3) than in those free of infection. In the IST withdrawal study, 10 of 22 liver transplant recipients have achieved complete withdrawal and 12 receive 50% of IST. So far, there have been eight rejections once IST began to be withdrawn. None of these patients had iATP in the strong immune response zone (risk of rejection).

CONCLUSIONS

iATP seems to be more effective in identifying overimmunosuppressed patients with a high risk of adverse events (IST-safety) than in identifying those with a high risk of rejection (IST-efficacy) and should be used in combination with other biomarkers of immunosuppressive effect to improve the efficacy of IST.

The pharmacokinetics of mycophenolate mofetil in renal transplant recipients receiving standard-dose or low-dose cyclosporine, low-dose tacrolimus or low-dose sirolimus: the Symphony pharmacokinetic substudy

BACKGROUND

Exposure to mycophenolic acid (MPA), the primary active metabolite of mycophenolate mofetil (MMF), is correlated with therapeutic efficacy of MMF but varies depending on the concomitantly administered immunosuppressive drugs.

METHODS

A 3-month pharmacokinetic substudy of the prospective, randomized, multicentre, open-label Symphony study was performed. Eighty-three adult renal transplant patients received standard-dose cyclosporine, MMF 2 g/day and corticosteroids, or daclizumab induction, MMF 2 g/day and corticosteroids plus low-dose cyclosporine, low-dose tacrolimus or low-dose sirolimus. The area under the concentration-time curve (AUC(0-12)) of MPA and its metabolites between treatment groups was compared. Pharmacokinetic sampling was performed before MMF administration and at 20, 40, 75 min; 2, 3, 6, 8, 10 and 12 h post-dose on Day 7 and Months 1 and 3.

RESULTS

Compared with standard-dose cyclosporine, patients receiving low-dose tacrolimus or low-dose sirolimus had significantly higher AUC(0-12) values for MPA at Day 7 and Month 1 and for free MPA at Day 7, and significantly lower AUC(0-12) values for 7-O-MPA-glucuronide (MPAG) at Month 1 and for acyl-glucuronide at Months 1 and 3 (P < 0.05). AUC(0-12) of MPA and free MPA was significantly greater with low-dose tacrolimus and low-dose sirolimus than with low-dose cyclosporine in the first month (P < 0.05). The ratio of MPA to MPAG exposure was significantly higher in the three low-dose groups than in the standard-dose cyclosporine group (P < 0.05).

CONCLUSIONS

Standard- and low-dose cyclosporine reduces the exposure of MPA and free MPA compared to low-dose tacrolimus or low-dose sirolimus in patients given the same dose of MMF.

Mapping similarities in mTOR pathway perturbations in mouse lupus nephritis models and human lupus nephritis

Introduction

Treatment with sirolimus, a mammalian target of rapamycin (mTOR) inhibitor, has been shown to be efficacious in the MRL/lpr and NZB × NZW F1 mouse models of lupus nephritis, indicating a critical role for the mTOR pathway in both models. This type of demonstration of efficacy in animal models is usually a pre-requisite for advancement into clinical development. However, efficacy in an animal model often has not translated to the desired activity in the clinic. Therefore, a more profound understanding of the mechanistic similarities and differences between various animal models and human diseases is highly desirable.

Methods

Transcriptional profiling was performed on kidneys from mice with lupus nephritis; from mice who had efficacious drug treatment; and from mice before they developed nephritis. Analysis of variance with false discovery rate adjusted to p < 0.05 and an average fold change of two or more was used to identify transcripts significantly associated with disease and response to therapy. Pathway analyses (using various bioinformatics tools) were carried out to understand the basis for drug efficacy in the mouse model. The relevance in human lupus of the pathways identified in the mouse model was explored using information from several databases derived from the published literature.

Results

We identified a set of nephritis-associated genes in mouse kidney. Expression of the majority of these returned to asymptomatic levels on sirolimus treatment, confirming the correlation between expression levels and symptoms of nephritis. Network analysis showed that many of these nephritis genes are known to interact with the mTOR pathway. This led us to ask what human diseases are linked to the mTOR pathway. We constructed the mTOR pathway interactome consisting of proteins that interact with members of the mTOR pathway and identified a strong association between mTOR pathway genes and genes reported in the literature as being involved in human lupus.

Conclusions

Our findings implicate the mTOR pathway as a critical contributor to human lupus. This broad pathway-based approach to understanding the similarities in, and differences between, animal models and human diseases may have broader utility.