The Banff 2017 Kidney Meeting Report: Revised diagnostic criteria for chronic active T cell-mediated rejection, antibody-mediated rejection, and prospects for integrative endpoints for next-generation clinical trials

The kidney sessions of the 2017 Banff Conference focused on 2 areas: clinical implications of inflammation in areas of interstitial fibrosis and tubular atrophy (i-IFTA) and its relationship to T cell-mediated rejection (TCMR), and the continued evolution of molecular diagnostics, particularly in the diagnosis of antibody-mediated rejection (ABMR). In confirmation of previous studies, it was independently demonstrated by 2 groups that i-IFTA is associated with reduced graft survival. Furthermore, these groups presented that i-IFTA, particularly when involving >25% of sclerotic cortex in association with tubulitis, is often a sequela of acute TCMR in association with underimmunosuppression. The classification was thus revised to include moderate i-IFTA plus moderate or severe tubulitis as diagnostic of chronic active TCMR. Other studies demonstrated that certain molecular classifiers improve diagnosis of ABMR beyond what is possible with histology, C4d, and detection of donor-specific antibodies (DSAs) and that both C4d and validated molecular assays can serve as potential alternatives and/or complements to DSAs in the diagnosis of ABMR. The Banff ABMR criteria are thus updated to include these alternatives. Finally, the present report paves the way for the Banff scheme to be part of an integrative approach for defining surrogate endpoints in next-generation clinical trials.

cPRA Increases With DQA, DPA, and DPB Unacceptable Antigens in the Canadian cPRA Calculator

A calculated panel reactive antibody (cPRA) estimates the percentage of donors with unacceptable antigens (UA) for a recipient. cPRA may be underestimated in transplant candidates with UA to DQA, DPA, and DPB if these are not included in the calculation program. To serve the National Canadian Transplant Programs, a cPRA calculator was developed with complete molecular typing for all donors at HLA-A, B, C, DRB1, DRB3/4/5, DQA1, DQB1, DPA1, and DPB1, all resolved to serologic equivalents. The prevalence of UA at DQA, DPA and DPB was evaluated in a sensitized regional population. The impact of adding these additional UA to cPRA was calculated alone and in combination, and compared to the baseline cPRA for UA at A, B, C, DR, DR51/52/53, and DQ. Of 740 sensitized transplant candidates, 18% of total and 32% with cPRA≥95% had DQA UA. Twenty-seven percent of total and 54% with cPRA≥95% had DPB UA. Of 280/740 subjects with these UA, 36/280 (13%) had cPRA increase of >20% when they were included, 7% increased cPRA to ≥80% and 6% to ≥95%. Inclusion of DQA, DPA, and DPB UA in Canadian cPRA calculations improves the accuracy of cPRA where these are relevant in allocation.

Interferon Gamma ELISPOT Testing as a Risk-Stratifying Biomarker for Kidney Transplant Injury: Results From the CTOT-01 Multicenter Study

Previous studies suggest that quantifying donor-reactive memory T cells prior to kidney transplantation by interferon gamma enzyme-linked immunosorbent spot assay (IFNγELISPOT) can assist in assessing risk of posttransplant allograft injury. Herein, we report an analysis of IFNγELISPOT results from the multicenter, Clinical Trials in Organ Transplantation-01 observational study of primary kidney transplant recipients treated with heterogeneous immunosuppression. Within the subset of 176 subjects with available IFNγELISPOT results, pretransplant IFNγELISPOT positivity surprisingly did not correlate with either the incidence of acute rejection (AR) or estimated glomerular filtration rate (eGFR) at 6- or 12-month. These unanticipated results prompted us to examine potential effect modifiers, including the use of T cell-depleting, rabbit anti-thymocyte globulin (ATG). Within the no-ATG subset, IFNγELISPOT(neg) subjects had higher 6- and 12-month eGFRs than IFNγELISPOT(pos) subjects, independent of biopsy-proven AR, peak PRA, human leukocyte antigen mismatches, African-American race, donor source, and recipient age or gender. In contrast, IFNγELISPOT status did not correlate with posttransplant eGFR in subjects given ATG. Our data confirm an association between pretransplant IFNγELISPOT positivity and lower posttransplant eGFR, but only in patients who do not receive ATG induction. Controlled studies are needed to test the hypothesis that ATG induction is preferentially beneficial to transplant candidates with high frequencies of donor-reactive memory T cells.

Should HLA mismatch acceptability for sensitized transplant candidates be determined at the high-resolution rather than the antigen level?

Defining HLA mismatch acceptability of organ transplant donors for sensitized recipients has traditionally been based on serologically defined HLA antigens. Now, however, it is well accepted that HLA antibodies specifically recognize a wide range of epitopes present on HLA antigens and that molecularly defined high resolution alleles corresponding to the same low resolution antigen can possess different epitope repertoires. Hence, determination of HLA compatibility at the allele level represents a more accurate approach to identify suitable donors for sensitized patients. This approach would offer opportunities for increased transplant rates and improved long term graft survivals.

Multicenter validation of urinary CXCL9 as a risk-stratifying biomarker for kidney transplant injury

Noninvasive biomarkers are needed to assess immune risk and ultimately guide therapeutic decision-making following kidney transplantation. A requisite step toward these goals is validation of markers that diagnose and/or predict relevant transplant endpoints. The Clinical Trials in Organ Transplantation-01 protocol is a multicenter observational study of biomarkers in 280 adult and pediatric first kidney transplant recipients. We compared and validated urinary mRNAs and proteins as biomarkers to diagnose biopsy-proven acute rejection (AR) and stratify patients into groups based on risk for developing AR or progressive renal dysfunction. Among markers tested for diagnosing AR, urinary CXCL9 mRNA (odds ratio [OR] 2.77, positive predictive value [PPV] 61.5%, negative predictive value [NPV] 83%) and CXCL9 protein (OR 3.40, PPV 67.6%, NPV 92%) were the most robust. Low urinary CXCL9 protein in 6-month posttransplant urines obtained from stable allograft recipients classified individuals least likely to develop future AR or a decrement in estimated glomerular filtration rate between 6 and 24 months (92.5-99.3% NPV). Our results support using urinary CXCL9 for clinical decision-making following kidney transplantation. In the context of acute dysfunction, low values can rule out infectious/immunological causes of injury. Absent urinary CXCL9 at 6 months posttransplant defines a subgroup at low risk for incipient immune injury.

Precision diagnostics in transplantation: from bench to bedside

The Canadian and American Societies of Transplantation held a symposium on February 22, 2012 in Quebec City focused on discovery, validation and translation of new diagnostic tools into clinical transplantation. The symposium focused on antibody testing, transplantation pathology, molecular diagnostics and laboratory support for the incompatible patient. There is an unmet need for more precise diagnostic approaches in transplantation. Significant potential for increasing the diagnostic precision in transplantation was recognized through the integration of conventional histopathology, molecular technologies and sensitive antibody testing into one enhanced diagnostic system.

Detection of clinical and subclinical tubulo-interstitial inflammation by the urinary CXCL10 chemokine in a real-life setting

Urinary CXCL10 is a promising noninvasive biomarker for tubulo-interstitial allograft inflammation, but its diagnostic characteristics have not been assessed in a real-life setting. We investigated urinary CXCL10 in 213 consecutive renal allograft recipients having 362 surveillance biopsies at 3/6 months and 80 indication biopsies within the first year posttransplant. Allograft histology results were classified as (i) acute Banff score zero, (ii) interstitial infiltrates only, (iii) tubulitis t1, (iv) tubulitis t2-3 and (v) isolated vascular compartment inflammation. For clinical and subclinical pathologies, urinary CXCL10 correlated well with the extent of tubulo-interstitial inflammation. To determine diagnostic characteristics of urinary CXCL10, histological groups were separated into two categories: no relevant inflammation (i.e. acute Banff score zero and interstitial infiltrates only) versus all other pathologies (i.e. tubulitis t1-3 and isolated vascular compartment inflammation). For subclinical pathologies, AUC was 0.69 (sensitivity 61%, specificity 72%); for clinical pathologies, AUC was 0.74 (sensitivity 63%, specificity 80%). A urinary CXCL10-guided biopsy strategy would have reduced performance of surveillance and indication biopsies by 61% and 64%, respectively. Missed (sub)clinical pathologies were mostly tubulitis t1 and isolated vascular compartment lesions. In real life, urinary CXCL10 had clinically useful diagnostic properties making it a candidate biomarker to guide allograft biopsies.

Lifetime probabilities of needing an organ transplant versus donating an organ after death

The lifetime probabilities of becoming a deceased organ donor and requiring or receiving an organ transplant are unknown. An actuarial analysis was performed in a representative Canadian sample. Using Canadian organ donation data 1999-2007, provincial waiting list and population census data, actuarial rates were produced that provide the probabilities, by age band and gender, of (1) becoming a deceased organ donor, (2) needing an organ transplant and (3) receiving all organs needed. Regardless of age, the lifetime probability of needing a transplant for males is approximately twice that of females. Depending on age, Canadians are five to six times more likely to need an organ transplant than to become a deceased organ donor. The lifetime probabilities of not receiving a required organ transplant, expressed as a percentage of individuals on the waiting list, ranges from approximately 30% at birth, 20 years and 40 years to approximately 40% at 60 years. Across provinces and genders, Canadians at all ages are much more likely to need an organ transplant than to become an organ donor. Approximately one-third of those in need of a transplant will never receive one. How this information may influence organ donation decisions is currently under study.

Urinary CXCL9 and CXCL10 levels correlate with the extent of subclinical tubulitis

Subclinical tubulitis has been associated with the later development of interstitial fibrosis and tubular atrophy (IF/TA), leading to diminished allograft survival. The aim of this study was to investigate how concentrations of urinary CXC-receptor 3 (CXCR3) chemokines (i.e. CXCL4/9/10/11) and CCL2 relate to the extent of subclinical tubulitis. Using ELISA, urinary CXCR3 chemokines, CCL2 and tubular injury markers (i.e. urinary NGAL and alpha1-microglobulin [alpha1 m]) were measured in patients with stable estimated GFR >or=40 mL/min exhibiting normal tubular histology (n = 24), subclinical borderline tubulitis (n = 18) or subclinical tubulitis Ia/Ib (n = 22), as well as in patients with clinical tubulitis Ia/Ib (n = 17) or IF/TA (n = 10). CXCL9 and CXCL10 were significantly higher in subclinical tubulitis Ia/Ib than in subclinical borderline tubulitis (p <or= 0.03) and normal tubular histology (p <or= 0.0002). By contrast, NGAL, alpha1-m, CXCL4, CXCL11 and CCL2 were not or only marginally distinctive across these patient groups. All urinary chemokines and tubular injury markers were higher in clinical tubulitis Ia/Ib than in normal tubular histology (p <or= 0.002), but only tubular injury markers were elevated in IF/TA. These results demonstrate a correlation of urinary CXCL9 and CXCL10 levels with the extent of subclinical tubulitis suggesting potential as noninvasive screening biomarkers.

Twenty-three novel HLA-B alleles identified during intermediate-resolution testing

Twenty-three novel human leukocyte antigen-B alleles are described: B*070204, *0738, *0742, *0821, *130202, *1312, *1575, *1598, *1599, *270507, *2728, *350104, *3558, *3811, *3931, *3932, *4045, *4107, *420501, *4812, *510106, *5520, and *5616. Thirteen of the variants are single-nucleotide substitutions from their most homologous allele, eight resulting in amino acid changes (B*0742, *1312, *1598, *1599, *3558, *3931, *4107, and *5616) and five with silent substitutions (B*070204, *130202, *270507, *350104, and *510106). Three alleles (B*0738, *4812, and *5520) differ by five nucleotide changes, altering four amino acids. The remaining seven alleles differ from their most similar alleles by two to three nucleotides, altering from one to two amino acids.

Cytokine genotypes correlate with pain and radiologically defined joint damage in patients with juvenile rheumatoid arthritis

OBJECTIVES

Single nucleotide polymorphisms (SNPs) in cytokine genes have been associated with risk of a number of autoimmune diseases. Moreover, some SNPs are associated with variations in rates of in vitro gene expression, and it is therefore possible that these functional polymorphisms may differentially affect inflammatory processes and disease outcome. This project's objective was to determine whether cytokine genotypes correlate with disease outcomes in patients with juvenile rheumatoid arthritis (JRA).

METHODS

Genotypes of SNPs of pro-inflammatory cytokines, tumour necrosis factor-alpha -308G -->A, interleukin-6 (IL-6) -174G -->C and interferon-gamma +874G -->A, and anti-inflammatory, immunosuppressive cytokines, interleukin-10 -1082G -->A, -819C -->T and -592A -->C and transforming growth factor-beta1 (TGF-beta1) codon 10T -->C and codon 25G -->C, were determined for patients with JRA who previously participated in a long-term outcome study. Cytokine genotypes and clinical variables showing significant correlations with clinical outcomes at the alpha = 0.100 level in univariate analyses were entered in multivariate tests.

RESULTS

In multivariate tests, the IL-6 genotype -174G/G was positively correlated with pain [regression coefficient B = 0.899, 95% confidence intervals (CI) 0.185, 1.612, P = 0.014]. The homozygous TGF-beta1 codon 25G/G genotype showed a protective effect against joint space narrowing on radiographs taken within 2 yr of disease onset, but confidence intervals were wide [odds ratio (OR) 0.176, 95% CI 0.037, 0.837 P = 0.029].

CONCLUSIONS

The correlation of IL-6 genotype with pain and the possible association of the TGF-beta1 codon 25 genotype with short-term radiographic damage (G/C with greater risk and G/G with decreased risk) suggests that both these polymorphisms may be useful early prognostic indicators. Further studies of the relation between cytokine genotypes and outcomes in patients with all forms of juvenile idiopathic arthritis (JIA) are warranted.

Differential cytokine genotype frequencies among Canadian Aboriginal and Caucasian populations

Genetic diversity related to the human immune response is a key factor in individual and population survival throughout human history. Population diversity in disease susceptibility and resistance have been identified and linked to differences in cytokine mRNA and protein expression levels. Polymorphisms in the regulatory regions of cytokine genes can influence gene transcription levels and they have been associated with susceptibility to, and/or severity of, autoimmune disorders such as rheumatoid arthritis, meningococcus and sepsis. It is reported here that in two study populations, Canadian Aboriginal individuals have a higher frequency of cytokine single-nucleotide polymorphisms favouring a low production of TNFalpha, IFNgamma and IL-10 and high production of IL-6 as compared to a Caucasian population. We postulate that the evolution of this unique cytokine genotype profile may be linked to the Aboriginal adaptation to selection pressures related to an environment in which helminthic, parasitic and fungal infections predominated.

The urine protein to creatinine ratio (P/C) as a predictor of 24-hour urine protein excretion in renal transplant patients

BACKGROUND

The purpose of this study was to examine the utility of the random urine protein to creatinine ratio (P/C) in evaluation and longitudinal management of proteinuria in adult renal transplant recipients with or without overt nephropathy in an outpatient clinic.

METHODS

A total of 289 adult renal transplant recipients provided 24-hr urine collections for total protein and creatinine, followed by a random urine for protein and creatinine. For longitudinal analysis, 192 of these patients provided two 24-hr urine collections with concomitant random urine specimens separated on average by 6.8 months. As well, 134 patients provided a total of 851 multiple-paired spot and 24-hr urine samples (range 2 to 12) over a 2-year period.

RESULTS

The log random urine P/C ratio correlated significantly to the log 24 UP (r=0.749, P<0.0001) with or without nephrotic range proteinuria. High sensitivity (74.4-90%) and specificity values (93-98%) were found for estimating proteinuria from 0.5 to 2 g/day. However, the precision of estimation decreased as the level of urinary protein excretion increased to >3 g/day. The positive predictive value decreased as proteinuria became >3 g/day, perhaps because of the low prevalence of patients with high level proteinuria in our sample. The direction of change in P/C ratio longitudinally was accompanied by a similar direction of change in 24 UP, which was highly significant (r=0.7555, P<0.0001).

CONCLUSION

We conclude that the urine P/C ratio is a useful and convenient screening and longitudinal test for proteinuria.

Neointimal and tubulointerstitial infiltration by recipient mesenchymal cells in chronic renal-allograft rejection

BACKGROUND

Tissue remodeling depends on mesenchymal cells (fibroblasts and myofibroblasts) and is a prominent feature of chronic renal-transplant rejection. It is not known whether the mesenchymal cells that participate in remodeling originate locally or from circulating precursor cells.

METHODS

We obtained biopsy specimens of renal allografts from six male recipients of an allograft from a female donor, four female recipients of an allograft from a male donor, two male recipients of an allograft from a male donor, and two female recipients of an allograft from a female donor. All the allografts were undergoing chronic rejection. All but two specimens were obtained within six months after transplantation. We used immunohistochemical methods to identify mesenchymal cells with smooth-muscle alpha-actin and in situ hybridization to identify mesenchymal cells with Y-chromosome DNA.

RESULTS

No Y-chromosome bodies were identified in the case of the two renal-allograft specimens in which both the donor and the recipient were female. In the case of the two renal-allograft specimens in which both the donor and the recipient were male, approximately 40 percent of mesenchymal cells contained a Y-chromosome body. In the case of the six specimens in which the donor was female and the recipient was male, a mean (+/-SD) of 34+/-16 percent of mesenchymal cells in the neointima, 38+/-12 percent of such cells in the adventitia, and 30+/-7 percent of such cells in the interstitium contained the Y-chromosomal marker, indicating that they originated from the recipient rather than the donor. In the case of the four renal-allograft specimens in which the donor was male and the recipient was female, the respective values were 24+/-15 percent, 33+/-9 percent, and 23+/-8 percent, indicating a persistent population of donor mesenchymal cells.

CONCLUSIONS

The presence of mesenchymal cells of host origin in the vascular and interstitial compartments of renal allografts undergoing chronic rejection provides evidence that a circulating mesenchymal precursor cell has the potential to migrate to areas of inflammation.

Subclinical rejection--a potential surrogate marker for chronic rejection--may be diagnosed by protocol biopsy or urine spectroscopy

Our studies of protocol biopsy studies have shown that normal allograft histology can not be assumed by crude tests of renal function such as the serum creatinine concentration, and that there is a high prevalence of subclinical rejection in the first 6 months post-transplant (7, 13-17). The apparent ability of urine MR and IR spectra to reliably identify patients with normal allograft histology, if confirmed in a larger database, will preclude the need for a protocol biopsy in approximately 20-50% of patients. Conversely, finding urine MR or IR spectra characteristic of subclinical rejection would provide the opportunity for early treatment. The clear separation between patients with normal histology from those with subclinical rejection can be attributed to the use of the whole urine spectrum to develop the classifiers. Additional advantages of using MR or IR spectra of urine as a diagnostic tool compared to the biopsy include simplicity (i.e. no processing is required), low cost, rapid turnaround (i.e. < 15 minutes/sample), and, particularly, low risk, thus allowing for repetitive sampling. The ability to non-invasively diagnose acute inflammation in the kidney would be of great assistance in the post-transplant monitoring of renal transplant patients. Indeed, by following subclinical inflammation as detected in the MR/IR spectra it will be possible to tailor the intensity of the immunosuppression to the inflammatory status of the graft, thus minimising the risks of both insufficient and excessive immunosuppression. Furthermore, by following subclinical inflammation, as detected in the MR/IR spectra, it will be possible to test the hypothesis that subclinical rejection (i.e. persistence of its MR/IR spectral classifier) is a surrogate marker for the development of chronic rejection.

Long-term allograft surveillance: the role of protocol biopsies

The safety of the renal allograft biopsy and the standardization of allograft histopathology interpretation have renewed interest in the performance of protocol (surveillance) biopsies. Recent surveillance biopsy studies in the areas of pre-implantation and in the early and late post-transplant periods are discussed.

Protocol biopsies in the management of renal allograft recipients

The safety of the renal allograft biopsy and the standardization of allograft histopathology interpretation have renewed interest in the protocol biopsy. Recent studies in the areas of 'marginal' donors, surveillance of acute rejection, molecular biology and chronic rejection are discussed.

Increased levels of GALbeta1-4GLCNACalpha2-6 sialyltransferase pretransplant predict delayed graft function in kidney transplant recipients

BACKGROUND

Galbeta1-4GlcNAcalpha2-6 sialyltransferase (ST6GalI) is an acute phase reactant whose release from cells can be induced by proinflammatory cytokines. Because patients with chronic renal failure have high circulating levels of proinflammatory cytokines, we hypothesized that patients on the renal transplant waiting list would have high circulating levels of ST6GalI, which might adversely affect post-transplant events.

METHODS

Levels of ST6GalI were measured in the serum of 70 patients immediately before renal transplant; these were correlated with posttransplant events, such as delayed graft function and rejection.

RESULTS

The mean serum level of ST6GalI was significantly higher in the patients (3162+/-97 U) than in 19 controls (2569 +/- 125 U; P<0.003). Patients who required dialysis posttransplant for treatment of delayed graft function (n=20) had significantly higher levels of ST6GalI pretransplant (3735+/-228 U) than patients (n=50) who did not require dialysis (2933+/-83 U; P<0.0001). In a multivariate analysis the ST6GalI level and cold ischemic time were found to be independent risk factors for the development of delayed graft function.

CONCLUSIONS

ST6GalI levels are high in renal failure patients awaiting a renal transplant and may be a risk factor for the development of delayed graft function. The assessment and perhaps modulation of a potential transplant recipient's ST6GalI systemic level may be beneficial.

Does subclinical rejection contribute to chronic rejection in renal transplant patients?

Renal allograft biopsies have traditionally been performed in the setting of acute graft dysfunction. However, several groups have performed graft biopsies at times of stable graft function, and more recently, after treatment of rejection episodes. Surprisingly, unequivocal histologic criteria for acute rejection have been demonstrated in a high proportion of these protocol biopsies. The Winnipeg Transplant Group has documented the high prevalence of clinically silent inflammatory infiltrates in early protocol biopsies, and demonstrated their inflammatory and cytotoxic potential by immunohistochemical and molecular biological techniques. Furthermore, in a randomized trial, our group has demonstrated that subclinical rejection, if untreated, is associated with the development of early chronic pathology and late graft dysfunction. In this overview, we will summarize the early data on subclinical allograft inflammation, present the experience of the Winnipeg Transplant Group, and discuss the possible implications of subclinical rejection on the development of chronic rejection.

Quantitation of allograft fibrosis and chronic allograft nephropathy

Despite improvements in the prevention and treatment of acute renal allograft rejection, the long-term survival of renal transplants has not increased. Immunologic and non-immunologic factors contribute to the gradual deterioration of graft function and to the histologic lesion characterized by vascular and interstitial fibrosis ('chronic rejection'). Quantitation of this process has been attempted using various invasive and non-invasive methods. These methods, performed at different times post-transplant, are reviewed in this article. In particular, pathology scoring systems and the potential of using computerized image analysis of biopsy material are discussed.

Effect of increasing baseline immunosuppression on the prevalence of clinical and subclinical rejection: a pilot study

This group has reported that treatment of subclinical rejection in the first 3 mo posttransplant with corticosteroids decreases late clinical rejections and improves graft function at 2 yr in renal transplant recipients. The current study was performed to determine whether an increase in baseline immunosuppression would decrease the prevalence of early subclinical rejections, as well as the incidence of early and late clinical rejections. Patients received mycophenolate mofetil (MMF) and Neoral cyclosporin A (CsA) posttransplant (n = 29), of which 17 underwent protocol biopsies at months 1, 2, 3, and 6 (Neoral + MMF Protocol Biopsy [Bx]), while 12 declined protocol biopsies (Neoral + MMF Control). These individuals were compared with 72 historical control patients treated with Sandimmune CsA and Imuran, of which 36 had undergone protocol biopsies at months 1, 2, 3, and 6 (Sandimmune + Azathioprine [AZA] Protocol Bx), and 36 had a protocol biopsy at month 6 (Sandimmune + AZA Control). Baseline immunosuppression with Neoral + MMF decreased the incidence of early clinical rejections (0 to 3 mo) and cumulative corticosteroid exposure, but had no impact on the prevalence of early subclinical rejection. Moreover, to maximally decrease the risk of developing late clinical rejections (months 7 to 12) in Neoral + MMF patients required that protocol biopsies be done and that subclinical rejection be treated. The paradoxical finding of recent clinical trials that a reduction in acute clinical rejection has not improved long-term graft outcome may be explained in part by the failure to control subclinical rejection.

Clinical rejection is distinguished from subclinical rejection by increased infiltration by a population of activated macrophages

It has been reported previously that one-third of protocol renal biopsies in asymptomatic, biochemically stable renal transplant recipients in the first 6 mo show unsuspected subclinical graft rejection (both infiltrate and tubulitis) and that subclinical rejection is a risk factor for chronic renal dysfunction. This study was performed to determine whether differences in phenotype or activation status of graft-infiltrating cells underlie these different manifestations of acute rejection. Biopsies with normal histology (n = 10), subclinical rejection (n = 13), and clinical rejection (n = 9) were studied using immunohistochemistry and computerized image analysis. Subclinical and clinical rejections had similar histologic Banff scores. Univariate analysis showed a trend for a higher infiltration with CD8+ (P = 0.053) and CD68+(P = 0.06) cells in clinical rejection. Of the activation markers studied (CD25, perforin, tumor necrosis factor-alpha), only allograft inflammatory factor-1+-activated macrophages were significantly (P = 0.014) increased in the infiltrate of clinical rejection biopsies. These data suggest that activated macrophages or their products are responsible for acute renal dysfunction associated with clinical rejection episodes.

Protocol biopsies in renal transplantation: research tool or clinically useful?

Early protocol biopsies of stable, well functioning renal allografts reveal a high prevalence of clinically unsuspected acute and chronic pathology. It is becoming increasingly apparent that these histopathological findings are both pathogenic and predictive of long-term allograft outcome. Therefore, protocol biopsies may be required for optimal post-transplant surveillance until non-invasive methods to detect allograft inflammation are developed.

Beneficial effects of treatment of early subclinical rejection: a randomized study

The prevalence of subclinical rejection, by the Banff criteria, is approximately 30% in the first 3 mo in renal transplant recipients. A randomized study was performed to determine whether the treatment of subclinical rejection with corticosteroids was associated with improved outcomes in these patients. Seventy-two patients, stratified by donor source, were randomized to biopsies at 1, 2, 3, 6, and 12 mo (Biopsy group), or to 6- and 12-mo biopsies only (Control group). Patients were analyzed by "intent to treat" and were followed for a minimum of 2 yr. Patients in the Biopsy arm of the study had a significant decrease in early (months 2 and 3) and late (months 7 to 12) acute rejection episodes, a reduced chronic tubulointerstitial score at 6 mo, and a lower serum creatinine at 24 mo than did patients in the Control arm. There was a trend toward an increase in infectious morbidity, but no increase in mortality, in the patients randomized to the Biopsy group. The results of this study suggest that early protocol biopsies and the treatment of subclinical rejection with corticosteroids may lead to better histologic and functional outcomes in renal transplant recipients.

Matching for private or public HLA epitopes reduces acute rejection episodes and improves two-year renal allograft function

BACKGROUND

The current role of HLA matching in renal transplantation is controversial. Public HLA epitope matching has been suggested to be as advantageous as private HLA matching, with the added benefit of increasing recipients' access to well-matched grafts.

METHODS

In this single-center study of 105 renal transplant recipients, we examined the association of HLA matching with early (0-3 months) and late (4-6 months) rejection episodes (RE), as well as renal allograft function up to 2 years after transplant.

RESULTS

Poor HLA-DR, but not HLA-A or -B, matching was associated with early RE (0 DR matches, RE=2.7+/-0.19, 1 DR match, RE=2.37+/-0.18, vs. 2 DR matches, RE=1.5+/-0.38; P < 0.01). In contrast, poor HLA-B, but not HLA-A or -DR, matching was associated with late rejections (0 HLA-B matches, RE=1.1+/-0.51 vs. 1-2 HLA-B matches, RE=0.51+/-0.1; P < 0.004). HLA-B matching was also associated with a significantly lower serum creatinine (SCr) level at 24 months (0 HLA-B matches, SCr=178+/-20 micromol/L vs. SCr=132+/-6 micromol/L for 1-2 HLA-B matches; P < 0.025). Matching for 10 supertypic HLA-A and -B cross-reactive groups was associated with reduced late graft rejection (0-2 residue matches, RE=1.15+/-0.18 vs. RE=0.62+/-0.12 for 3 to 7 residue matches; P < 0.013) as well as a significantly lower SCr level at 24 months (0-2 residue matches, SCr=205+/-29 micromol/L vs SCr=131+/-6 micromol/L for 3 to 7 residue matches; P < 0.001) after transplantation.

CONCLUSIONS

HLA-DR matching was associated with a reduced frequency of early rejection episodes, whereas HLA-B or residue/cross-reactive group matching was associated with a reduced frequency of late rejection episodes and improved graft function at 2 years.

Identification of clinical and histopathologic risk factors for diminished renal function 2 years posttransplant

The aim of this study was to identify early clinical and pathologic variates that independently predict diminished renal allograft function at 24 mo posttransplant. A clinical pathologic data base was prospectively derived from 71 patients in whom protocol renal biopsies were performed at 1, 2, 3, 6, and 12 mo posttransplant. The major end point was the 24-mo serum creatinine. Variates correlating independently (r2 = 0.67) with the 24-mo serum creatinine were the chronic biopsy scores (months 3 and 6), late rejections (months 4 to 6), cyclosporin A (CsA) levels (months 1 to 2), and delayed graft function. The adjusted odds ratio (OR) and 95% confidence interval (CI) for having a serum creatinine > or = 130 mumol/L at 24 mo increased for every year the donor age increased (OR = 1.07; 95% CI, 1.02 to 1.13; range, 9 to 55) or for each late rejection episode (OR = 5.9; 95% CI, 1.7 to 20.1), whereas a mean CsA level > 300 micrograms/L from months 1 to 3 was protective (OR = 0.07; 95% CI, 0.01 to 0.43). Variates correlating independently (r2 = 0.53) with the change in serum creatinine from 6 to 24 mo (delta Cr6-24) were the chronic biopsy scores at months 3 and 6. The adjusted OR of the delta Cr6-24 rising > or = +20 mumol/L increased for every year the donor age increased (OR = 1.09; 95% CI, 1.02 to 1.16; range 9 to 56) or when the 6-mo chronic biopsy score was > or = 2 (OR = 6.6; 95% CI, 1.2 to 36.4). An estimate of the relative risk for diminished renal function at 2 yr can be assigned within 6 mo of transplant based on chronic pathology, late acute rejections, CsA levels, and donor age.

CTLA4Ig prevents lymphoproliferation and fatal multiorgan tissue destruction in CTLA-4-deficient mice

Mice lacking CTLA-4 develop a fatal spontaneous lymphoproliferative disease with massive lymphocytic infiltrates and tissue destruction in many organs. CTLA-4-deficient (-/-) splenocytes and lymph node cells proliferate without added stimuli in vitro. We report here that CTLA4Ig treatment of CTLA-4 -/- mice prevents lymphoproliferation and fatal multiorgan tissue damage in vivo and proliferation of CTLA-4 -/- splenocytes and lymph node cells in vitro. Therefore, stimulation via CD28-B7 interactions appears necessary for CTLA-4 -/- T cell proliferation and the production of lymphoproliferative disease in vivo. When CTLA4Ig treatment is terminated, CTLA-4 -/- T cells become activated and lymphoproliferative disease develops. The lack of long term protective effects of CTLA4Ig treatment suggests that CTLA-4 is needed for the induction and or maintenance of tolerance.

CTLA4Ig prevents lymphoproliferation and fatal multiorgan tissue destruction in CTLA-4-deficient mice

Mice lacking CTLA-4 develop a fatal spontaneous lymphoproliferative disease with massive lymphocytic infiltrates and tissue destruction in many organs. CTLA-4-deficient (-/-) splenocytes and lymph node cells proliferate without added stimuli in vitro. We report here that CTLA4Ig treatment of CTLA-4 -/- mice prevents lymphoproliferation and fatal multiorgan tissue damage in vivo and proliferation of CTLA-4 -/- splenocytes and lymph node cells in vitro. Therefore, stimulation via CD28-B7 interactions appears necessary for CTLA-4 -/- T cell proliferation and the production of lymphoproliferative disease in vivo. When CTLA4Ig treatment is terminated, CTLA-4 -/- T cells become activated and lymphoproliferative disease develops. The lack of long term protective effects of CTLA4Ig treatment suggests that CTLA-4 is needed for the induction and or maintenance of tolerance.

Prolonged islet allograft acceptance in the absence of interleukin 4 expression

Murine CTLA4/Fc therapy leads to permanent engraftment of islet allografts in interleukin 4 (IL-4) knockout (IL-4-/- mice. Interestingly, IL-4+/- hosts were more resistant to tolerance induction than IL-4-/- mice. An IL-2/Fc fusion protein abrogates the effect of CTLA4/Fc therapy while an IL-4/Fc fusion protein tends to inhibit rather than enhance the effect of CTLA/Fc treatment in IL-4-/- recipients. We conclude that allograft acceptance requires principally a blockade of T cell activation rather than 'immune deviation' of the T cell activation program to Th2 cytokines (i.e. IL-4).

Cytokines and the Th1/Th2 paradigm in transplantation

With studies elucidating the cytokine programs associated with T-cell activation, allograft rejection and tolerance induction, the Th1/Th2 paradigm has become a unifying model to explain the observed cytokine profiles. The proof that these cytokines mediate allograft tolerance, however, is at best indirect. More recent studies highlighting the redundant and pleiotropic nature of cytokine networks suggest that the Th1/Th2 paradigm may not be sufficient to explain fully the mechanisms underlying allograft tolerance.

Obstructive sleep apnea in association with posterior fossa neurologic disease

Sleep apnea in association with neurologic disease is uncommon, and its documentation with nocturnal polysomnography (PSG) is rare. Two patients with posterior fossa neurologic disease had obstructive and central sleep apnea on PSG. The first was a 40-year-old woman who experienced a respiratory arrest ten days after neurosurgical decompression of a cervical syrinx associated with syringobulbia. Nocturnal PSG demonstrated obstructive sleep apnea. Tracheostomy was performed and a second nocturnal PSG showed no sleep apnea. The second patient was a 76-year-old woman with daytime hypersomnolence, nocturnal choking spells, progressive spastic paraparesis, and left-sided cerebellar tremor. Neurologic evaluation led to the diagnosis of olivopontocerebellar degeneration. Nocturnal PSG showed multiple episodes of central and obstructive apnea. These cases support the hypothesis that central and obstructive sleep apnea can originate from a central mechanism.