Microchimerism in sensitized renal patients.

BACKGROUND: Patients exposed to allogeneic human tissue sometimes produce anti-HLA antibody for many years in the absence of further obvious antigen exposure. To investigate the mechanism of sustained sensitization, we identified females awaiting renal transplantation with high panel-reactive antibody but no exposure to allogeneic tissue for at least 1 month. METHODS: We analyzed peripheral blood microchimerism using nested polymerase chain reaction amplification specific for the SRY region of the Y chromosome. RESULTS: Microchimerism was detected in 3 of 10 patients but in none of 8 normal female subjects. In two cases, the amplified DNA polymerase chain reaction product was sequenced and was confirmed to be identical to the SRY gene. The estimated level of chimerism as compared with serial dilutions of DNA from male peripheral blood leukocytes was about 1/50000. CONCLUSION: These results do not establish causality but support the possibility that antigens from microchimeric donor cells may sustain the HLA antibody response in certain patients.     

Is obesity still a risk factor in renal transplantation?

At our center, since 1982, a body mass index (BMI) of less than 30 has been a prerequisite for placing a patient on the waiting list for renal transplantation. This decision was made because obese transplant recipients seemed to have a less than favorable post-transplant outcome. The aim of this study was to evaluate whether this requirement is still justified. Forty-six patients with a BMI above 30 underwent primary cadaveric renal transplantation between 1972 and 1993. For each of these obese patients, five consecutive non-obese (BMI 20–25) control patients were selected. Patient and graft survival, causes of graft loss, and acute rejection rate were evaluated for the two patient groups before and after the year 1982. Within the first 30 post-transplant days, one patient (2 %) and 11 grafts (24 %) were lost in the group of obese patients whereas seven patients (3 %) and 36 grafts (16 %) were lost in the control group. Among the obese patients, renal circulatory complications were a major cause of graft loss. In the period 1973–1981, the 1-year patient survival rate was 65 % among obese patients versus 75 % among controls from 1982 to 1993, this was 90 % versus 93 %. From 1973 to 1981, the 1-year graft survival rate was 25 % among obese patients versus 53 % among controls (P < 0.05); from 1982 to 1993, it was 68 % versus 84 % (P = NS). Multivariate analysis showed that the immunosuppressive regimen, age of the patient, BMI, and cold ischemia time of the graft had a significant influence on graft survival. The acute rejection rate within the first 30 days was 28 % among obese patients and 35 % among controls (P = NS). We conclude that a BMI below or equal to 30 is still justified as a prerequisite for placement on the waiting list for renal transplantation, for despite an overall improvement, the outcome of renal transplantation in obese patients remains worse than that in non-obese patients. Received: 3 February 1997 Received after revision: 4 April 1997 Accepted: 8 April 1997     

Delayed graft function: a frequent but still unsolved problem in renal transplantation

Delayed graft function (DGF) is a frequent and well-known complication of renal transplantation, which occurs in 30% of cadaver kidney allografts. It has an economic cost that is the result of prolonged patient hospitalization and the need for hemodialysis sessions; it also increases the risk of acute allograft rejection and may affect long-term graft survival. Lots of risk factors were identified, like donor hemodynamic compromise or prolonged cold ischemia time; however, incidence of DGF remains high due to the frequent use of marginal donors due to organ shortage. Recent advances in the pathophysiology of DGF point the importance of the ischemia-reperfusion injury mechanisms and some therapeutics that may reduce them are under investigation, like the use of new solutions to improve organ preservation and the use of some antioxidant and anti-inflammatory drugs.     

Renal response to a protein load persists during long-term follow-up of children after renal transplantation

BACKGROUND: Kidney donors and transplant recipients may be at risk of complications from glomerular hyperfiltration of the single kidney. It has been assumed that tests of the existence of renal functional reserve [delta glomerular filtration rate (deltaGFR), delta effective renal plasma flow (deltaERPF)] can be used to demonstrate hyperfiltration. It would therefore be of interest to evaluate the response of the kidney graft to a protein load. i.e., testing the renal reserve and to find out whether a reduction in baseline GFR is preceded by a loss of deltaGFR. METHODS: We repeatedly studied the change in GFR and renal plasma flow (ERPF) after an oral protein load in 30 children after renal transplantation (Tx). Follow-up time was 1.0-8.0 years. Renal function was evaluated with the clearances of inulin and para-aminohippuric acid (PAH). Seven recipient/donor pairs were examined twice (median 0.3 and 4 years, after Tx). RESULTS: The baseline GFR and ERPF remained stable throughout the follow-up and the increase after stimulation (deltaGFR and deltaERPF) did not change in the whole group of Tx children over the years. However, a reduction in the baseline GFR from the first to the last investigation occurred in 23 of 30 children. In the 23 patients whose baseline GFR decreased, deltaGFR was still preserved. In the recipient/donor pairs, the baseline GFR and ERPF were the same, but on the second investigation, donors showed higher deltaGFR. CONCLUSION: Despite fairly low baseline GFR and ERPF values in the Tx children, no change occurs in the capacity to increase GFR and ERPF after a protein load during follow-up, which suggests that they are not maximally hyperfiltrating.     

微嵌合假说与肝移植供者造血细胞输注

1　微嵌合假说的提出196 9年 ,Ｋａｓｈｉｗａｇｉ等通过核型分析发现在移植的肝脏中 ,网状内皮细胞为受者细胞取代 ,而肝细胞和血管内皮细胞仍为供者型 ,首次提出了器官移植嵌合体的观点 ,以后许多研究都证实了这种嵌合状态的存在 ,但均限于植入的器官内。 1992年 ,Ｓｔａｒｚ     

Chronic kidney disease is still present after renal transplantation with excellent function

According to a k/DOQI work group, chronic kidney disease (CKD) can be present also in subjects with glomerular filtration rate (GFR) >90 mL/min or a serum creatinine (sCr) below 1.3 mg/dL. The aim of this study was to document the prevalence of clinical or biologic abnormalities among 190 cadaveric renal transplant patients with excellent and stable renal function at 6 months after transplantation as well as 5 years later. The recipients were 82 women and 108 men of mean age at transplantation of 44.56 +/- 11.73 years. All patients were on Neoral-based immunosuppression with at least 5-year follow-up. Mean sCr was 1.18 +/- 0.2 mg/dL. Mean GFR was 78.57 +/- 27.06 mL/min. Systolic blood pressure was >130 mm Hg in 56.6%, although 78.3% of patients were on antihypertensive therapy; 34.3% were anemic; 75.4% had serum cholesterol >200 mg/dL; 62.2% had serum triglyceride levels >170 mg/dL. Serum intact parathyroid hormone >100 pg/mL was observed in 38% of patients and 43% were on vitamin D supplementation, and 11.4% had developed posttransplant diabetes mellitus. With respect to controls, von Willebrand factor was higher in 81.2% (P < .0001; RR = 11); serum homocysteine levels in 75% (P < 0.001; RR = 7.61); PAI-1 in 37.5% (P = .0009; RR = 4). At 5 years posttransplantation we observed an overall improvement in these abnormalities. The vast majority of renal transplant patients with excellent graft function belong to stage 1 of CKD being affected by hypertension, dyslipidemia, anemia, and residual hyperparathyroidism. Markers of endothelial dysfunction were largely abnormal, a condition that could predispose to cardiovascular events.     

Microchimerism does not induce tolerance and sustains immunity after in utero transplantation

BACKGROUND: To date, over 40 in utero transplants have been performed in humans; the only successes were documented in the treatment of severe combined immunodeficiency syndromes. Hemoglobinopathies and metabolic disorders are candidate diseases for this approach; however, when applied clinically, the results have been discouraging. To address the role of the fetal immune system in the outcome of in utero transplantation, we have developed a murine model of in utero transplantation in immunologically intact murine recipients and have studied chimerism and tolerance/immunity to allogeneic donor cells through the lives of the animals. METHODS: We have performed experiments in which purified murine sca-1+/lin- cells and c-kit+/lin- cells of C57BL/6 (H2b) mice were injected into Balb/c (H2d) fetal recipients at early gestational ages. Chimerism was tested by highly sensitive semiquantitative polymerase chain reaction assay and tolerance/immunity to donor cells was studied by in vivo (skin grafts, responses to postnatal boosts) and in vitro (mixed lymphocyte culture, cytotoxicity, and cytokine release) assays. RESULTS: One hundred percent (10/10) of mice transplanted with c-kit+ cells and 44% (4/9) of mice transplanted with sca+ cells showed circulating donor cells within the first 6 months of life (P=0.031). Mice in the sca+ group rejected donor skin grafts at a mean time of 9.1+/-0.2 days, whereas mice in the c-kit+ group rejected donor skin grafts at a mean time of 15.1+/-0.7 days (P=0.001). The difference between the transplanted groups and non-transplanted controls was also significant (P<0.05). All mice transplanted with sca+/lin- cells showed greater response to donor cells than to third-party cells at all effector to target ratios (P=0.002). Differences in response to donor alloantigen between sca+ and c-kit+ groups were significant (P=0.003). Cytokine quantification demonstrated higher TH1 than TH2 cytokine release in all groups, and the response to donor cells was higher in the sca+ compared with c-kit+ mice (P=0.031). CONCLUSION: These results demonstrate a low level of chimerism and tolerance in mice transplanted in utero with sca+/lin- and c-kit+/lin- cells. The possibility of active in utero immunization to donor cells is supported by accelerated skin graft rejection in mice transplanted with sca+ cells and enhanced in vitro immune responses in mice with persistent microchimerism.     

Malignancy after kidney transplantation: still a challenge

Long-term complications of continuous immunosuppression still remain a serious threat and are currently drawing the attention of transplant physicians. Wimmer et al. show that malignancy occurs approximately fourfold more frequently in renal-transplant recipients than in a normal control population. Besides immunosuppression, viruses probably play an important oncogenic role in transplant recipients. The retrospective analysis by Wimmer et al. suggests that mTOR inhibitors and interleukin-2 receptor antibodies are promising immunosuppressive drugs to reduce the risk of cancer after transplantation. These preliminary results must be confirmed in large, prospective, randomized, controlled trials, with long follow-up, designed to evaluate the incidence of de novo malignancy in transplant recipients.     

Microchimerism evaluation in recipients of living-related or unrelated deceased allograft renal transplants

The presence of microchimerism in the peripheral blood of solid organ graft recipients has been associated with long-term solid organ acceptance, immunologic tolerance, and less aggressive immunosuppressive therapy. Molecular biology assays are among the most sensitive methods to detect microchimerism, primarily to evaluate Y chromosome sequences in females as indirect evidence of circulating male nucleated donor cells. We screened for the presence of the SRY sequence region in peripheral blood of 13 female recipients of male kidney grafts: 5 living-related and 8 deceased grafts. Only patients who received grafts from related living donors exhibited microchimerism. Five of 13 patients studied exhibited better graft outcomes, including the 4 who were positive for the SRY sequences.     

Race and end-stage renal disease in the United States Medicare population: the disparity persists

Aim: A marked preponderance of end-stage renal disease among African Americans was described more than two decades ago. The objective of this study was to determine whether racial disparities in end-stage renal disease in the United States have changed over time. Methods: The authors compared renal replacement therapy rates in five biennial cohorts (1993–1994, 1995–1996, 1997–1998, 1999–2000, 2001–2002; n = 6 315 283), using annual random samples of 5% of the US Medicare population and the United States Renal Data System registry. Results: The proportion of African American subjects rose from 8.8% in the first cohort to 9.4% in the last. Renal replacement therapy rates (per 1000 patient-years) among white Americans in successive cohorts were 0.84, 0.96, 1.08, 1.16 and 1.20, compared with 2.98, 3.24, 3.65, 3.80 and 3.57 among African Americans (P < 0.0001 for race comparison within each biennial cohort). Corresponding hazards ratios, adjusted for demographic characteristics and comorbid conditions, were 2.01 (95% confidence interval 1.82–2.33), 1.96 (1.78–2.17), 2.00 (1.81–2.20), 2.01 (1.83–2.21) and 1.86 (1.69–2.04), suggesting the absence of meaningful reduction in racial disparities in renal replacement therapy rates over time. Conclusion: Disparities in renal replacement therapy rates between white and African American Medicare beneficiaries have persisted over time.     

Microchimerism after liver transplantation: absence of rejection without abrogation of anti-donor cytotoxic T-lymphocyte-mediated alloreactivity.

Microchimerism (MC) is defined by the persistence of <1% circulating donor cells resulting from cell migration from the graft; MC may play a role in the induction of unresponsiveness to allogeneic tissues, or may be merely the consequence of the graft's acceptance following immunosuppression. To analyze early MC (7 patients) and late MC (12 patients) following a liver transplantation, we designed a sensitive and semiquantitative nested polymerase chain reaction (PCR) protocol based on the detection of incompatible human leukocyte antigen (HLA)-DRB1 donor alleles. MC was measured in multiple PCR samples and expressed as percent positive PCRs / time point. The detection level was 1 donor cell / 10(5) patient cells. All patients had detectable early MC, ranging from 5 to 100% positive PCRs in the 1st 3 months after transplantation. The kinetic analysis demonstrated that MC decreased during the 1st year in 6 of 7 patients. All of the 4 patients with the lowest MC had rejection episodes, vs. none among the 3 patients with MC >50%. However, cytotoxic T-lymphocyte reactivity (CTL) against HLA class I donor antigens could be demonstrated 1 year posttransplant in 2 patients with a high level of early MC. MC is a dynamic process, which is easily detectable <3 months after liver transplantation. In conclusion, a correlation between the level of early MC and the absence of rejection episodes was observed. However, high levels of early MC did not abrogate the persistence of an alloreactive response measured in vitro 1 year after transplantation, which suggests that MC did not lead to clonal deletion of donor-specific CTL.