关于Rejection — More Than the Eye Can See的原因,关于Rejection — More Than the Eye Can See的相关知识。 In comparing current clinical outcomes in renal transplantation with those of 30 years ago,1 graft failure from immunologic factors and death from opportunistic infection in the first year after transplantation are no longer common clinical outcomes. The therapeutic regimens used today to prevent and treat rejection or infection among renal-transplant recipients bear only a small resemblance to those used 30 years ago.
In contrast, the diagnostic strategies used to detect rejection and distinguish it from other causes of renal dysfunction have not budged during the past two decades. A rise in the level of serum creatinine suggests allograft dysfunction, but the reasons can be elusive. Nephrotoxicity from immunosuppressive agents may cause acute and chronic allograft dysfunction, and accordingly, clinicians attempt to maintain drug levels in the therapeutic range. To aid in the resolution of the difficult differential diagnosis of allograft dysfunction, ultrasonography and renal biopsy are often performed.
This reactive diagnostic approach is often too late, and there are limitations because, first, drug levels do not test how therapy is affecting the recipient's immune response, and second, biopsies lack sensitive histologic patterns for the diagnosis of drug-induced nephrotoxicity and early rejection. Furthermore, detecting adverse host antigraft immunity before there is evidence of graft dysfunction has not been feasible. Since the diagnosis of rejection is made after the advent of renal damage, it is not surprising that the necessarily late application of antirejection therapy often results in only partial restoration of renal-transplant function. Serial surveillance biopsies of the transplant, a maneuver that would undoubtedly detect some instances of subclinical rejection,2 are precluded by cost and complication-related issues.
The advent of reverse transcriptase polymerase chain reaction and DNA-microarray technology has allowed for highly sensitive, accurate, and quantitative detection of the transcriptional profiles of tissue samples from recipients3,4,5,6,7,8,9,10,11,12and donors,13 thereby enabling the discovery of a molecular signature for acute cellular rejection.3,4,5,6,7,8,9,10,11,12 Acute allograft rejection is characterized by infiltration of the allograft by activated T cells. Accordingly, expression of T-cell–activation genes is evident in renal-transplant biopsy specimens obtained from patients who are undergoing transplant rejection.2,4,5,6,7,8,9,10,11,12Knowing that activated donor-specific cytotoxic T lymphocytes (CTLs) infiltrate rejecting allografts, the expression of T-cell–activation genes that control the cytolytic machinery of activated CTLs was first analyzed in renal-transplant biopsy specimens.4,5,6
Since the transplant is infiltrated by a T-cell–rich population of mononuclear leukocytes, robust intragraft expression of the T-cell–specific T-cell antigen receptor7 and T-cell–specific CD38 genes are excellent markers for rejection. Nonetheless, infiltration with other mononuclear leukocytes is also noted during rejection. Particularly interesting is the observation that amplified expression of the B-cell–specific CD20 gene in the context of robust expression of CTL-related genes and other activation genes provides a molecular signature for rejection episodes that are resistant to corticosteroid therapy.9
To enhance the use of transcriptional profiling methods, noninvasive techniques that do not rely on renal biopsy are desired. In fact, the molecular signature of rejection, amplified expression of CTL genes, can be detected in circulating blood cells at the time of rejection.10 A drawback to the use of circulating blood is that blood cannot be used to analyze the heterogeneous population of mononuclear leukocytes that infiltrate rejecting allografts. In contrast, under most circumstances, lymphocytes that are present in the urine of patients with renal transplants have traversed the kidney before entering the urine flow. A notable innovation of Suthanthiran and colleagues has been the clever use of urine-sediment cells for transcriptional profiling studies.8 Parallel studies comparing renal-transplant biopsy specimens and urine-sediment cells reveal a similar sensitivity and specificity of gene expression for CTL-effector molecules, CD3, and other genes for the diagnosis of rejection.8 In this issue of the Journal, the Suthanthiran group has extended these studies in the study by Muthukumar et al.,3 which reaffirms that amplified expression of CD3 (a T-cell-lineage–specific transcript), perforin (an activated CTL transcript), and CD25 (a T-cell–activation transcript) is far more robustly expressed in urine-sediment cells from renal-transplant recipients with acute rejection than in cells from patients with either chronic rejection or a normal biopsy.3
In addition, Muthukumar et al. have carefully studied FOXP3 gene expression. Expression of the FOXP3 gene, a member of the forkhead family of cell-differentiation genes, is a lineage-specific transcript for graft-protecting regulatory T cells.14 FOXP3 is the master switch that turns on the immunosuppressive properties of regulatory T cells.14 The finding that increased FOXP3 expression is a correlate of rejection is somewhat of a surprise. The molecular footprints for both cytopathic and protective cells are detected in T cells that have traversed the kidney and are collected from the urine sediment.3 Thus, the complex nature of immune response to the kidney transplant at the cellular level is made evident by the lineage-specific gene expression detected within urinary-sediment cells. Rejection is orchestrated by cytopathic, tissue-injuring CD4+ helper type 1 and CD8+ CTL T cells, but the study by Muthukumar et al. demonstrates that some FOXP3-positive protective T cells are also present within the graft during rejection.
The revelation in the new study is the remarkable ability of FOXP3 transcript levels to predict clinical outcomes. Although the molecular signature of rejection is present, low expression of FOXP3 at the time of rejection forewarns that rejection is severe and may not readily respond to antirejection therapy. Moreover, low expression of FOXP3 identifies transplants at heightened risk of graft failure within six months. Higher FOXP3 transcript levels at the time of rejection, despite the molecular signature of rejection, heralds a more favorable clinical outcome. It is notable that the histologic grade of rejection (Banff score) does not predict the severity or clinical outcome of treated rejection episodes. Why? Pathological examination of a transplant biopsy can measure the magnitude and scope of graft infiltration by leukocytes, but routine pathological analysis is not informative as to the cellular program (destructive or protective) of the graft-infiltrating cells.
In animal studies, therapeutic regimens that successfully induce donor-specific tolerance and thereby allow the safe withdrawal of immunosuppressive therapy serve to tip the balance of immunity from the predominant cytopathic-type antidonor immunity detected in untreated hosts toward the enduring ascendancy of protective-type immunity.15 The clinical data arising from the report of Muthukumar et al., taken together with experimental data, strengthen and add texture to the concept that the balance of cytopathic-type immunity to protective-type immunity determines both gross and subtle clinical outcomes, even in hosts receiving daily immunosuppressive therapy.
The potential for molecular diagnostic techniques to predict renal-transplant rejection, the safety of drug withdrawal, and other long-term and short-term outcomes may be substantial. The influence of assessing the molecular status of renal transplants in the operating room on later clinical outcome is also being analyzed.13 Overall, molecular diagnostic strategies are being tested in multicenter clinical trials sponsored by the National Institutes of Health and the Immune Tolerance Network. If the validity of these methods can be confirmed, the door to more effective and individualized therapy will be wide open. The present definition of "successful" treatment of a rejection episode is a loss of renal function of less than 15 percent. It would be a great improvement if the techniques described by Muthukumar et al. could lead to preemptive anticipation of problems and fully successful therapy.
Dr. Strom reports serving as a member of the Immune Tolerance Network.
Source Information
From the Harvard Medical School, Beth Israel Deaconess Medical Center, Boston.
References
Tilney NL, Strom TB, Vineyard GC, Merrill JP. Factors contributing to the declining mortality rate in renal transplantation. N Engl J Med 1978;299:1321-1325.
Rush D, Nickerson P, Jeffrey J. Protocol biopsies in the management of renal allograft recipients. Curr Opin Nephrol Hypertens 2000;9:615-619.
Muthukumar T, Dadhania D, Ding R, et al. Messenger RNA for FOXP3 in the urine of renal-allograft recipients. N Engl J Med 2005;353:2342-2351.
Lipman ML, Stevens AC, Strom TB. Heightened intragraft CTL gene expression in acutely rejecting renal allografts. J Immunol 1994;152:5120-5127.
Lipman ML, Stevens AC, Bleackley RC, et al. The strong correlation of cytotoxic T lymphocyte-specific serine protease gene transcripts with renal allograft rejection. Transplantation 1992;53:73-79.
Strehlau J, Pavlakis M, Lipman M, et al. Quantitative detection of immune activation transcripts as a diagnostic tool in kidney transplantation. Proc Natl Acad Sci U S A 1997;94:695-700.
Pavlakis M, Lipman M, Strom TB. Intragraft T cell receptor transcript expression in human renal allografts. J Am Soc Nephrol 1995;6:281-285.
Li B, Hartono C, Ding R, et al. Noninvasive diagnosis of renal-allograft rejection by measurement of messenger RNA for perforin and granzyme B in urine. N Engl J Med 2001;344:947-954.
Sarwal M, Chua MS, Kambham N, et al. Molecular heterogeneity in acute renal allograft rejection identified by DNA microarray profiling. N Engl J Med 2003;349:125-138.
Vasconcellos LM, Schachter AD, Zheng XX, et al. Cytotoxic lymphocyte gene expression in peripheral blood leukocytes correlates with rejecting renal allografts. Transplantation 1998;66:562-6.
Sarwal MM, Jani A, Chang S, et al. Granulysin expression is a marker for acute rejection and steroid resistance in human renal transplantation. Hum Immunol 2001;62:21-31.
Pavlakis M, Strehlau J, Lipman M, Shapiro M, Maslinski W, Strom TB. Intragraft IL-15 transcripts are increased in human renal allograft rejection. Transplantation 1996;62:543-545.
Avihingsanon Y, Ma N, Pavlakis M, et al. On the intraoperative molecular status of renal allografts after vascular reperfusion and clinical outcomes. J Am Soc Nephrol 2005;16:1542-1548.
Rudensky A. Foxp3 and dominant tolerance. Philos Trans R Soc Lond B Biol Sci 2005;360:1645-1646.
Zheng XX, Sanchez-Fueyo A, Sho M, Domineg C, Sayegh MH, Strom TB. Favorably tipping the balance between cytopathic and regulatory T cells to create transplantation tolerance. Immunity 2003;19:503-514. (文章出处：《新英格兰医药杂志》)
In contrast, the diagnostic strategies used to detect rejection and distinguish it from other causes of renal dysfunction have not budged during the past two decades. A rise in the level of serum creatinine suggests allograft dysfunction, but the reasons can be elusive. Nephrotoxicity from immunosuppressive agents may cause acute and chronic allograft dysfunction, and accordingly, clinicians attempt to maintain drug levels in the therapeutic range. To aid in the resolution of the difficult differential diagnosis of allograft dysfunction, ultrasonography and renal biopsy are often performed.
This reactive diagnostic approach is often too late, and there are limitations because, first, drug levels do not test how therapy is affecting the recipient's immune response, and second, biopsies lack sensitive histologic patterns for the diagnosis of drug-induced nephrotoxicity and early rejection. Furthermore, detecting adverse host antigraft immunity before there is evidence of graft dysfunction has not been feasible. Since the diagnosis of rejection is made after the advent of renal damage, it is not surprising that the necessarily late application of antirejection therapy often results in only partial restoration of renal-transplant function. Serial surveillance biopsies of the transplant, a maneuver that would undoubtedly detect some instances of subclinical rejection,2 are precluded by cost and complication-related issues.
The advent of reverse transcriptase polymerase chain reaction and DNA-microarray technology has allowed for highly sensitive, accurate, and quantitative detection of the transcriptional profiles of tissue samples from recipients3,4,5,6,7,8,9,10,11,12and donors,13 thereby enabling the discovery of a molecular signature for acute cellular rejection.3,4,5,6,7,8,9,10,11,12 Acute allograft rejection is characterized by infiltration of the allograft by activated T cells. Accordingly, expression of T-cell–activation genes is evident in renal-transplant biopsy specimens obtained from patients who are undergoing transplant rejection.2,4,5,6,7,8,9,10,11,12Knowing that activated donor-specific cytotoxic T lymphocytes (CTLs) infiltrate rejecting allografts, the expression of T-cell–activation genes that control the cytolytic machinery of activated CTLs was first analyzed in renal-transplant biopsy specimens.4,5,6
Since the transplant is infiltrated by a T-cell–rich population of mononuclear leukocytes, robust intragraft expression of the T-cell–specific T-cell antigen receptor7 and T-cell–specific CD38 genes are excellent markers for rejection. Nonetheless, infiltration with other mononuclear leukocytes is also noted during rejection. Particularly interesting is the observation that amplified expression of the B-cell–specific CD20 gene in the context of robust expression of CTL-related genes and other activation genes provides a molecular signature for rejection episodes that are resistant to corticosteroid therapy.9
To enhance the use of transcriptional profiling methods, noninvasive techniques that do not rely on renal biopsy are desired. In fact, the molecular signature of rejection, amplified expression of CTL genes, can be detected in circulating blood cells at the time of rejection.10 A drawback to the use of circulating blood is that blood cannot be used to analyze the heterogeneous population of mononuclear leukocytes that infiltrate rejecting allografts. In contrast, under most circumstances, lymphocytes that are present in the urine of patients with renal transplants have traversed the kidney before entering the urine flow. A notable innovation of Suthanthiran and colleagues has been the clever use of urine-sediment cells for transcriptional profiling studies.8 Parallel studies comparing renal-transplant biopsy specimens and urine-sediment cells reveal a similar sensitivity and specificity of gene expression for CTL-effector molecules, CD3, and other genes for the diagnosis of rejection.8 In this issue of the Journal, the Suthanthiran group has extended these studies in the study by Muthukumar et al.,3 which reaffirms that amplified expression of CD3 (a T-cell-lineage–specific transcript), perforin (an activated CTL transcript), and CD25 (a T-cell–activation transcript) is far more robustly expressed in urine-sediment cells from renal-transplant recipients with acute rejection than in cells from patients with either chronic rejection or a normal biopsy.3
In addition, Muthukumar et al. have carefully studied FOXP3 gene expression. Expression of the FOXP3 gene, a member of the forkhead family of cell-differentiation genes, is a lineage-specific transcript for graft-protecting regulatory T cells.14 FOXP3 is the master switch that turns on the immunosuppressive properties of regulatory T cells.14 The finding that increased FOXP3 expression is a correlate of rejection is somewhat of a surprise. The molecular footprints for both cytopathic and protective cells are detected in T cells that have traversed the kidney and are collected from the urine sediment.3 Thus, the complex nature of immune response to the kidney transplant at the cellular level is made evident by the lineage-specific gene expression detected within urinary-sediment cells. Rejection is orchestrated by cytopathic, tissue-injuring CD4+ helper type 1 and CD8+ CTL T cells, but the study by Muthukumar et al. demonstrates that some FOXP3-positive protective T cells are also present within the graft during rejection.
The revelation in the new study is the remarkable ability of FOXP3 transcript levels to predict clinical outcomes. Although the molecular signature of rejection is present, low expression of FOXP3 at the time of rejection forewarns that rejection is severe and may not readily respond to antirejection therapy. Moreover, low expression of FOXP3 identifies transplants at heightened risk of graft failure within six months. Higher FOXP3 transcript levels at the time of rejection, despite the molecular signature of rejection, heralds a more favorable clinical outcome. It is notable that the histologic grade of rejection (Banff score) does not predict the severity or clinical outcome of treated rejection episodes. Why? Pathological examination of a transplant biopsy can measure the magnitude and scope of graft infiltration by leukocytes, but routine pathological analysis is not informative as to the cellular program (destructive or protective) of the graft-infiltrating cells.
In animal studies, therapeutic regimens that successfully induce donor-specific tolerance and thereby allow the safe withdrawal of immunosuppressive therapy serve to tip the balance of immunity from the predominant cytopathic-type antidonor immunity detected in untreated hosts toward the enduring ascendancy of protective-type immunity.15 The clinical data arising from the report of Muthukumar et al., taken together with experimental data, strengthen and add texture to the concept that the balance of cytopathic-type immunity to protective-type immunity determines both gross and subtle clinical outcomes, even in hosts receiving daily immunosuppressive therapy.
The potential for molecular diagnostic techniques to predict renal-transplant rejection, the safety of drug withdrawal, and other long-term and short-term outcomes may be substantial. The influence of assessing the molecular status of renal transplants in the operating room on later clinical outcome is also being analyzed.13 Overall, molecular diagnostic strategies are being tested in multicenter clinical trials sponsored by the National Institutes of Health and the Immune Tolerance Network. If the validity of these methods can be confirmed, the door to more effective and individualized therapy will be wide open. The present definition of "successful" treatment of a rejection episode is a loss of renal function of less than 15 percent. It would be a great improvement if the techniques described by Muthukumar et al. could lead to preemptive anticipation of problems and fully successful therapy.
Dr. Strom reports serving as a member of the Immune Tolerance Network.
Source Information
From the Harvard Medical School, Beth Israel Deaconess Medical Center, Boston.
References
Tilney NL, Strom TB, Vineyard GC, Merrill JP. Factors contributing to the declining mortality rate in renal transplantation. N Engl J Med 1978;299:1321-1325.
Rush D, Nickerson P, Jeffrey J. Protocol biopsies in the management of renal allograft recipients. Curr Opin Nephrol Hypertens 2000;9:615-619.
Muthukumar T, Dadhania D, Ding R, et al. Messenger RNA for FOXP3 in the urine of renal-allograft recipients. N Engl J Med 2005;353:2342-2351.
Lipman ML, Stevens AC, Strom TB. Heightened intragraft CTL gene expression in acutely rejecting renal allografts. J Immunol 1994;152:5120-5127.
Lipman ML, Stevens AC, Bleackley RC, et al. The strong correlation of cytotoxic T lymphocyte-specific serine protease gene transcripts with renal allograft rejection. Transplantation 1992;53:73-79.
Strehlau J, Pavlakis M, Lipman M, et al. Quantitative detection of immune activation transcripts as a diagnostic tool in kidney transplantation. Proc Natl Acad Sci U S A 1997;94:695-700.
Pavlakis M, Lipman M, Strom TB. Intragraft T cell receptor transcript expression in human renal allografts. J Am Soc Nephrol 1995;6:281-285.
Li B, Hartono C, Ding R, et al. Noninvasive diagnosis of renal-allograft rejection by measurement of messenger RNA for perforin and granzyme B in urine. N Engl J Med 2001;344:947-954.
Sarwal M, Chua MS, Kambham N, et al. Molecular heterogeneity in acute renal allograft rejection identified by DNA microarray profiling. N Engl J Med 2003;349:125-138.
Vasconcellos LM, Schachter AD, Zheng XX, et al. Cytotoxic lymphocyte gene expression in peripheral blood leukocytes correlates with rejecting renal allografts. Transplantation 1998;66:562-6.
Sarwal MM, Jani A, Chang S, et al. Granulysin expression is a marker for acute rejection and steroid resistance in human renal transplantation. Hum Immunol 2001;62:21-31.
Pavlakis M, Strehlau J, Lipman M, Shapiro M, Maslinski W, Strom TB. Intragraft IL-15 transcripts are increased in human renal allograft rejection. Transplantation 1996;62:543-545.
Avihingsanon Y, Ma N, Pavlakis M, et al. On the intraoperative molecular status of renal allografts after vascular reperfusion and clinical outcomes. J Am Soc Nephrol 2005;16:1542-1548.
Rudensky A. Foxp3 and dominant tolerance. Philos Trans R Soc Lond B Biol Sci 2005;360:1645-1646.
Zheng XX, Sanchez-Fueyo A, Sho M, Domineg C, Sayegh MH, Strom TB. Favorably tipping the balance between cytopathic and regulatory T cells to create transplantation tolerance. Immunity 2003;19:503-514. (文章出处：《新英格兰医药杂志》)