Direct versus indirect allorecognition: Visualization of dendritic cell distribution and interactions during rejection and tolerization.

Interactions of donor and recipient dendritic cells (DCs) with CD4+ T cells determine the alloantigenic response in organ transplantation, where recipient T cells respond either directly to donor MHC, or indirectly to processed donor MHC allopeptides in the context of recipient MHC molecules. The present study evaluates donor and recipient alloantigen-presenting DC trafficking and their interactions with CD4+ T cells in the lymph nodes (LNs) and the spleen under tolerogenic treatment with anti-CD2 plus anti-CD3 mAb compared with untreated rejecting conditions. CX3CR1(GFP) BALB/c (I-A(d)) donor hearts were transplanted into C57BL/6 (I-A(b)) mice and quantification of donor DC direct (GFP+ or I-A(d+)) and recipient DC indirect (YAe+) trafficking and interactions with host CD4+ T cells was performed by fluorescent microscopy. Our data indicate that although both direct and indirect interactions between CD4+ T cells and donor and recipient DCs occur shortly after engraftment, only indirect presentation persists in the LN, but not the spleen, of tolerized recipients. These data suggest that distinct anatomic lymphoid compartments play a critical role in peripheral tolerance induction and maintenance, and persistent indirect presentation to CD4+ T cells within the LNs is an important process during tolerization.

Novel immunosuppressive agents in tolerance induction.

Induction of transplantation tolerance remains a much sought-after but elusive goal with a potential promise of rendering patients free of long-term immunosuppressive drugs while maintaining good organ transplant function indefinitely. All currently studied strategies toward transplantation tolerance include using immunosuppressive agents for a limited time period to achieve tolerance. There are a growing number of agents that lend themselves to tolerance induction and these agents are considered herein. Such agents generally fall into the categories of lymphocyte depletion, costimulation blockade, and adjunctive agents such as rapamycin. Preliminary data using donor stem cells suggests that embryonic stem cells may have substantial advantages over conventional donor bone marrow for tolerance induction. These preliminary results are briefly reviewed as well. Tolerance has been achieved in a small number of organ transplant patients and such successes suggest that progress in the clinical arena is happening and is an obtainable result.

Identification and characterization of the antigen-specific subpopulation of alloreactive CD4+ T cells in vitro and in vivo.

We report the identification and characterization of the small subpopulation of alloantigen-specific T cells in vitro and in vivo. This subpopulation of T cells was distinguished by up-regulation of cell surface CD4 expression. These CD4high T cells were alloantigen specific in proliferation assays in vitro, and they expressed memory/activation markers, including CD44high and CD69high. Further studies demonstrated that these allospecific CD4high cells were also present (< or = 1% of CD4+ T cells) in vivo in BALB/c (H-2d) recipients of C57BL/6 (H-2b) skin allografts. CD4high T cells isolated from regional draining lymph nodes in these skin graft recipients reacted in a donor-specific fashion to C57BL/6 splenocyte stimulator cells in mixed lymphocyte culture. Adoptive transfer of CD4high, but not CD4normal T cells, just before skin engraftment in CD4 knockout mice, reconstituted rejection. The discovery that a small subpopulation of CD4high lymph node cells contained all of the alloantigen-specific T cells may allow study of tissue-specificity and subsequent alloantigen identification in transplantation.

Significance of detecting Epstein-Barr-specific sequences in the peripheral blood of asymptomatic pediatric liver transplant recipients.

Pediatric allograft recipients are at increased risk for Epstein-Barr virus (EBV)-associated illnesses. The early identification and diagnosis of EBV-associated disorders is critical because disease progression can often be curtailed by modification of immunosuppression. We have previously shown that detection of EBV-specific sequences in the circulation by polymerase chain reaction (PCR) correlated well with the clinical symptoms of EBV infection. The purpose of the current study is to determine the significance of detecting EBV-specific sequences by PCR in asymptomatic pediatric liver transplant recipients. Peripheral-blood DNA was analyzed for the EBV genes, coding from the nuclear antigen 1 (EBNA-1) and the viral capsid antigen (gp220) by PCR. Samples from asymptomatic pediatric liver transplant recipients were analyzed from the immediate postoperative period and at 2- to 4-month intervals thereafter. We followed up 13 of these asymptomatic recipients who tested positive for EBV compared with 7 asymptomatic recipients who tested negative for EBV during the early posttransplantation period. Follow-up ranged from 1.5 to 4 years posttransplantation. Nine patients (69%) initially positive for EBV and asymptomatic ultimately developed symptoms of EBV infection, including fever, lymphadenopathy, rash, respiratory and gastrointestinal symptoms, and/or hepatitis. Five of these patients (56%) went on to develop posttransplant lymphoproliferative disorder based on histological examination of biopsied tissue and immunohistochemical identification of the EBV antigen/DNA in tissue. This is the first report suggesting that detection of EBV-specific sequences in the absence of symptoms may herald impending EBV-associated disorders. Thus, routine monitoring for circulating EBV sequences in asymptomatic recipients may be useful in the early identification of those at risk for developing EBV-associated disease and its ultimate prevention.

Power Doppler imaging of acute renal transplant rejection.

PURPOSE: We evaluated the usefulness of power Doppler imaging (PDI) in diagnosing acute renal-transplant rejection. METHODS: Twenty-eight patients underwent 33 renal-transplant biopsies for suspected acute rejection. Patterns of renal parenchymal vascularity revealed by PDI in patients with abnormal biopsy results were compared with patterns in a group who had normal biopsy results. PDI examinations were reviewed retrospectively by 2 independent radiologists who had no knowledge of the biopsy results. A PDI diagnosis of acute rejection required marked vascular pruning in both the cortex and medulla. PDI results then were compared with transplant-biopsy results. RESULTS: The sensitivity and specificity of PDI for diagnosing acute renal-transplant rejection were 40% and 100%, respectively. None of the patients with negative biopsy results had PDI abnormalities. The negative predictive value of PDI was 33%, and the positive predictive value was 100%. CONCLUSIONS: In our study, an abnormal sonogram was highly predictive of acute transplant rejection. However, a normal sonogram did not exclude the possibility of rejection.

Prolongation of cardiac graft survival with anti-CD4Ig plus hCTLA4Ig in primates.

BACKGROUND: The aim of this study was to determine whether the use of combined immunotherapy with a brief course of humanized anti-CD4Ig and hCTLA4Ig would prolong heterotopic cardiac allograft survival in primates (rhesus monkeys). This model was based on work in "high responder" rats where a brief course of depletive anti-CD4mAb plus hCTLA4Ig was successful in inducing transplantation tolerance. METHODS: Heterotopic cardiac transplants were performed in rhesus recipients. Donor/recipient pairs between groups were confirmed to be reactive prior to transplantation by MLR matching. Humanized anti-CD4Ig, a recently developed anti-CD4mAb, was given at a dose of 20 mg/kg i.v. on days -3, -2, -1, and 0. hCTLA4Ig was administered at 6 mg/kg/dose i.v. on days 0 and 2 for the first recipient and days 0, 2, 4, and 6 for the second recipient. No further immunosuppression was administered. The treated (n = 2) or untreated (n = 5) recipients were followed for graft function by daily palpitation. RESULTS: Treatment with anti-CD4Ig plus hCTLA4Ig resulted in a significant prolongation of heart graft survival (42 days for the first recipient and 52 days for the second recipient) compared to untreated recipients (7 days x 4, 11 days x 1). FACS analysis demonstrated CD4 depletion of anti-CD4 treated animals to <2% on posttransplant day 1. The CD4+ T cells gradually repopulated to 50-70% pretransplant levels just prior to rejection. No adverse responses (fever, tachypnea, tachycardia, infections) were observed. CONCLUSIONS: These are the first results demonstrating that a brief course of combined specific induction immunotherapy with humanized anti-CD4Ig plus hCTLA4Ig, in the absence of adjuvant posttransplant immunosuppression, was well tolerated and resulted in marked prolongation of cardiac allograft survival in primates.

Outcomes in diabetic patients after simultaneous pancreas-kidney versus kidney alone transplantation.

BACKGROUND: Previous studies have identified more morbidity in simultaneous pancreas-kidney (SPK) transplant recipients compared with kidney alone (KA) recipients. With the development of novel immunosuppressive drugs, studies are needed to determine optimal treatment regimens in specific patient populations. METHODS: We retrospectively compared short-term outcome in diabetic patients receiving either SPK or KA transplantation from December 10, 1991, to July 31, 1996. The SPK recipients received either cyclosporine (CsA) + azathioprine (AZA), FK506+AZA, or FK506 + mycophenolate mofetil (MM). KA group patients received either CsA+AZA or CsA+MM. RESULTS: Recipients of SPK instead of KA transplants were younger, had a longer mean length of stay, had a decreased incidence of delayed graft function, and had more readmissions. There were no significant differences in serum creatinine at 1, 2, and 3 years after transplantation, number of rejection episodes and infections, incidence of kidney graft loss and patient death, and 1- and 3-year actuarial patient and kidney graft survival rates between the two groups. Diabetic SPK patients receiving FK506+MM had a higher mean 3-month creatinine clearance (calculated), compared with recipients of CsA+AZA or FK506+AZA. Diabetic patients after KA transplantation who received CsA+MM demonstrated fewer rejection episodes and graft losses, although differences did not reach statistical significance. CONCLUSIONS: (1) Diabetic SPK recipients have decreased rates of delayed graft function and more readmissions compared with diabetic KA recipients. (2) There is no difference in: serum creatinine levels up to 3 years after transplantation, number of rejection episodes or infections, and 1- and 3-year patient and graft survival rates between SPK and KA recipients. (3) Short-term outcome is improved in diabetic recipients of SPK and KA transplants receiving MM instead of AZA.

Rat pancreatic islet and skin xenograft survival in CD4 and CD8 knockout mice.

The relative contributions of the CD4+ and CD8+ T cell subpopulations in xenotransplant rejection were studied using CD4 and CD8 knockout (KO) mice. Wistar Furth (WF, RT1a) rat pancreatic islet or skin xenografts were transplanted into either CD4 or CD8 KO recipients and compared to wild-type controls. Long-term survival of WF islet xenografts was observed in the CD4 KO mice (MST, >66+/-8 days) whereas CD8 KO mice rejected their islet xenografts within 8 days, similar to controls (MST, 7+/-0.2 days). In contrast, WF skin xenografts were rejected in both CD4 and CD8 KO recipients within 8 days. CD4 KO recipients which maintained xenoislets >90 days posttransplant rejected WF skin grafts within 9 days, without rejecting their original islet xenografts. These results suggest that CD4+ cells are essential for mediating islet xenograft rejection. These data also suggest that the absence of either CD4+ or CD8+ T cells is not sufficient to prevent rejection of skin xenografts.

Coexistence of Th1- and Th2-type cytokine profiles in anti-CD2 monoclonal antibody-induced tolerance.

Anti-CD2 monoclonal antibody OX34 has been shown to suppress immunity in rodents in vitro and in vivo. To evaluate the effects of OX34 on vascularized allografts, Lewis (RT1(1)) hearts were transplanted heterotopically into Wistar Furth (RT1(u)) rats. A single 5 mg/kg intraperitoneal dose of OX34 administered at transplantation induced indefinite graft survival (mean survival time >140.3+/-12.3 vs. 12.7+/-0.7 control, P=0.001). The mixed lymphocyte response was partially inhibited at 60 days after transplant, returning to normal at 100 days. Donor-specific tolerance was confirmed by acceptance of second donor (>100 days, n=2) and rejection of third-party (mean survival time: 7.5+/-0.5 days, n=2) hearts. Immunohistochemical staining of allograft tissue from tolerant animals demonstrated abundant CD2+, CD4+, and CD8+ graft-infiltrating cells. To elucidate further the nature of these cells, we compared the expression of interleukin (IL)-2, IL-4, IL-10, and interferon (IFN)-gamma mRNA in allografted tissue from tolerant, acutely rejecting (AR), isografted, and naive animals using nonisotopic in situ hybridization. A significant increase in IL-2, IL-4, IL-10, and IFN-gamma mRNA was observed in graft-infiltrating cells of both tolerant and AR animals. IL-10 mRNA expression 4 days after transplant was significantly elevated in the OX34-treated compared to AR recipients. These data demonstrate that a single dose of OX34 at engraftment induces tolerance to vascularized allografts. Expression of both T helper 1 and T helper 2 cytokine mRNA profiles (IL-2/IFN-gamma and IL-4/ IL-10, respectively) are up-regulated locally in graft-infiltrating cells of AR and tolerant animal allografts.

CD4+ but not CD8+ cells are essential for allorejection.

The generation of knockout mice with targeted gene disruption has provided a valuable tool for studying the immune response. Here we describe the use of CD4 and CD8 knockout mice to examine the role of CD4+ and CD8+ cells in initiating allotransplantation rejection. Pretreatment with a brief course of depletive anti-CD4 monoclonal antibody therapy allowed permanent survival of heart, but not skin, allografts transplanted across a major histocompatibility barrier. However, skin as well as heart grafts were permanently accepted in the CD4 knockout mice. Transfer of CD4+ cells into CD4 knockout recipient mice 1 d before skin engraftment reconstituted rejection, demonstrating that CD4+ cells are necessary for initiating rejection of allogeneic transplants. Major histocompatibility complex disparate heart and skin allografts transplanted into CD8 knockout recipients were rejected within 10 d. This study demonstrates that CD4+ but not CD8+ T cells are absolutely required to initiate allograft rejection.

Cardia allograft unresponsiveness using a posttransplant strategy : characterization of the graft infiltrate.

We evaluated a combined posttransplant strategy using antilymphocyte serum (ALS) at time of engraftment followed by low dose total lymphoid irradiation (TLI) and donor bone marrow cell (BMC) inoculation administered either intrathymically (IT) or intravenously (IV) in the vigorously rejecting strain combination DA into Lew recipients. Allograft survival was significantly prolonged with administration of ALS in combination with TLI and IT (105 +/- 28.6 days) or IV (106.8 +/- 28.6 days) BMC compared to administration of ALS combined with either TLI (17.8 +/- 0.4 days) or BMC (9.0 +/- 0.0 days), or TLI combined with BMC (1 1.5 +/- 0.5 days) (P < 0.000 1, experimental vs control animals). There was no difference in survival between those animals who underwent IT or IV BMC inoculation. Third-party (WF) BMC inoculation did not significantly prolong allograft survival (10.0 +/- 1.0 days). A mild to moderate cellular infiltrate was present in allograft tissue after 100 days. To further characterize these cells, cytokine mRNA expression in allograft tissue (> 100 days posttransplant) was evaluated using nonisotopic in situ hybridization. A similar cytokine profile was demonstrated in allograft tissue compared to naive and isograft tissue, except for a slight increase in IL-2 (P < 0.02, control vs IV BMC; P = NS, other groups). In summary, unresponsiveness was induced in a high-responder strain combination using a combined posttransplant strategy of ALS, TLI, and donor antigen either IT or IV. The cytokine profile of the graft infiltrating cells was similar to that of normal tissue. Unresponsiveness may be the result of functional inactivation of these cells.

Differential localization of allograft nitric oxide synthesis: comparison of liver and heart transplantation in the rat model.

Nitric oxide (NO) is a free radical with a diversity of cellular origins and potential functions. Within the realm of solid organ transplantation, NO has been the focus of much attention. Discordant reports have documented both suppression and potentiation of the alloimmune response. In addition to questions regarding its functional role, little is known of the cellular origins of NO in acute rejection of vascularized allografts. To address this question, acute rejection models of rat heterotopic heart and orthotopic liver transplantation were chosen. When compared with naive controls and isografted animals, acute rejection in both heart and liver transplantation was associated with elevated systemic levels of the NO metabolite, nitrite. This was accompanied by increased graft content of iNOS protein as determined by immunoblot analysis of protein extracts. Expression of iNOS mRNA was localized with in situ hybridization. In both heart and liver transplantation, iNOS mRNA was found in the inflammatory infiltrate accompanying acute rejection. In addition, hepatocytes also expressed iNOS mRNA in the rejecting liver allograft. In contrast, cardiac myocytes in the rejecting heart allograft did not stain for iNOS mRNA. These results indicate that organ-specific, differential cellular expression of iNOS occurs in the acutely rejecting allograft. Transcriptional regulation of iNOS may vary among various organs according to the local cellular milieu. In addition, there may be a variable allograft specific response to acute rejection which may modify the associated immunologic biology.

Estrogen-specific target site identified by progesterone-11 alpha-hemisuccinate-(2-[125I]-iodohistamine) in mouse brain membranes.

Using photoaffinity labeling with the progesterone analogue, progesterone-11 alpha-hemisuccinate-(2-[125I]-iodohistamine) ([125I]-his-PG), we identified and characterized a protein band of MW 29 kDa (p29) in mouse cerebellar membranes whose labeling is markedly inhibited by estrogens. Inhibition of the labeling was specific with respect to steroid structure. Labeling was strongly inhibited by estradiol-17 beta, estradiol-17 alpha, and the anti-estrogen tamoxifen and the synthetic estrogen diethylstilbestrol. Other estrogens (estriol, estrone) were less effective and the steroids, dihydroandrosterone, androsterone and aldosterone were ineffective. Preincubation with estradiol-17 alpha or estradiol-17 beta inhibited the labeling in a dose-dependent manner with IC50 values of 0.3 and 2.0 microM, respectively. The extent of labeling was three times as high in cerebellar membranes from males as from females. In males, labeling of cerebellar membranes was greater than that of cortex or limbic region. The labeling pattern of p29 was also different in membranes prepared from cerebellum, heart and liver. Moreover, PG enhanced the labeling of p29 in liver demonstrating a tissue-specific mode of interaction. The present results characterize p29 as a membrane-bound estrogen target site.

The utility of retroperitoneal kidney placement in simultaneous kidney pancreas transplantation.

Simultaneous kidney-pancreas (SPK) transplantation has become an accepted therapeutic modality for patients with Type I diabetes mellitus-mediated end-stage renal disease (ESRD). However, the intraperitoneal placement of the renal allograft may pose technical problems when attempting percutaneous biopsy or Doppler ultrasound examination. Recently, the Stanford University Transplant Center adopted the technique of retroperitoneal placement of the renal allograft with intraperitoneal placement of the pancreas allograft (RETRO). From August 1993 to August 1994, a total of 12 patients underwent SPK with this new technique. Twelve patients who had received SPK with the standard technique served as historical controls (INTRA). Demographic data, follow-up, operative time, creatinine and amylase on discharge, length of stay, intraoperative fluid requirements, rejection episodes, thrombotic complications, infections, and number of open and closed renal biopsies were compared between the two groups. Average length of follow-up was greater in the INTRA group (29.3 +/- 1.7 vs. 15.9 +/- 1.1 months). In addition, the RETRO group had significantly fewer open renal biopsies (1/15) in comparison to the INTRA group (7/12) (p < 0.001). The two groups otherwise did not differ in any of the parameters studied. We conclude that retroperitoneal kidney and intraperitoneal pancreas allograft placement is associated with a significantly decreased requirement for open renal biopsy with its associated operating room and anesthetic costs. In addition, the option of transcystoscopic or percutaneous needle biopsy of the pancreas allograft is preserved. This technique should be considered as an alternative to intraperitoneal placement of both the pancreas and renal allografts.

Interferon-gamma and interleukin-10 messenger RNA are up-regulated after orthotopic liver transplantation in tolerant rats: evidence for cytokine-mediated immune dysregulation.

BACKGROUND: Immune regulation requires antigen recognition, signaling, activation, secretion of cytokines, and effector function by lymphocytes. Although there is redundancy in the activation and function of the immune response, some cytokines simultaneously promote and suppress different pathways of immunity. In the experiments reported here we compare cytokine gene expression within liver allografts from tolerant rats with normal and isografted liver tissue. We also compare the secretion of interferon-gamma (IFN-gamma) in the supernatant from mixed lymphocyte cultures by using peripheral blood lymphocytes stimulated against donor antigen. METHODS: Orthotopic liver transplantations were performed using the cuff technique without hepatic artery revascularization. Nonisotopic in situ hybridization (ISH) was used to detect and localize messenger RNA to specific cells within tissue. Antisense DNA probes were generated to interleukin-2 (IL-2), IL-4, IL-10, and IFN-gamma. One-way mixed lymphocyte cultures were set up against irradiated donor splenocytes, and the supernatant was collected to measure IFN-gamma by enzyme-linked immunosorbent assay. RESULTS: Expression of IFN-gamma and IL-10 was up-regulated in tolerant animals versus normal or isografted liver (p = 0.0002 and 0.0001, IFN-gamma and IL-10, respectively). In situ hybridization localized the expression of messenger RNA predominantly to the cytoplasm of the hepatocytes. Levels of IFN-gamma were higher in the supernatant from proliferating peripheral lymphocytes against donor antigen from tolerant animals versus naive control animals. CONCLUSIONS: Expression of IFN-gamma and IL-10 is up-regulated in hepatocytes from allograft tissue after orthotopic liver transplantation. We believe that the up-regulation of IL-10 cross-regulates the effector function of IFN-gamma and supports cytokine-mediated immune dysregulation, which may be a mechanism of tolerance after orthotopic liver transplantation in rats.

Photoaffinity labeling with progesterone-11 alpha-hemisuccinate- (2-[125I]iodohistamine) identifies four protein bands in mouse brain membranes.

The radiolabeled progesterone (PG) analogue progesterone-11 alpha-hemisuccinate-(2-[125I]iodohistamine) was used to label PG binding proteins in brain membranes from mouse cerebellum. Photoaffinity labeling and sodium dodecyl sulfate-polyacrylamide gel electrophoresis identified specific PG binding protein bands 1-4 of 64-29 kDa. Bands 1 and 4 were well resolved on the gel and easily quantified. Preincubation with PG inhibited photolabeling in a dose-dependent manner. The labeling was specific with respect to steroid structure. For band 1, the extent of inhibition of labeling by PG and 3 alpha, 5 alpha-pregnanolone (3 alpha) was pronounced. Other steroids such as testosterone (Tes), estradiol (Est), and corticosterone (Cor) were less effective, whereas pregnenolone sulfate (PS) and cholesterol (Cho) were ineffective. With respect to band 4, Est was the most effective; PG, 3 alpha, and Tes were intermediate; and PS, Cho, and Cor were ineffective. The results describe specific membrane proteins that bind PG (band 1) and Est (band 4).

Early hernia repair in the premature infant: long-term follow-up.

The incidence of inguinal hernia and incarceration is high among premature infants. Optimal timing, anesthetic technique, and long-term results of hernia repair in hospitalized premature infants remain undefined. The authors reviewed the records of 52 consecutively treated premature infants who underwent bilateral inguinal herniorrhaphy under general anesthesia before discharge from the intensive care nursery. There were no significant differences in gestational age, birth weight, age and weight at time of surgery, or presence of preoperative apnea or bradycardia in between infants extubated within 24 hours and those intubated for more than 24 hours. Twenty-four infants (46%) were available for follow-up of 24 months or more (mean follow-up period, 57 months). One recurrence was identified, representing 4% of the long-term follow-up group and 2% of the initial population. Two patients had asymmetric testicular volumes suggestive of unilateral atrophy. The short- and long-term results suggest that repair under general anesthesia can be safely performed before discharge from the intensive care nursery.