摘要:

BackgroundIt has been suggested that T cells primed by processed donor major histocompatibility complex antigen (the “indirect” pathway of allorecognition) may be responsible for mediating chronic allograft rejection. The purpose of this study was to develop a clinically useful assay to study the occurrence of indirect allorecognition during chronic rejection in humans.MethodsA panel of 20 mer peptides corresponding to the hypervariable regions of HLA-DRB1*0101, DRB1*1501, and DRB1*0301 were synthesized. Lymphocytes obtained from renal allograft recipients were cocultured with these peptides. Proliferation was assayed by DNA incorporation of [3H]thymidine, and positive proliferation was defined by a statistically significant increase in counts per minute over background with a minimum stimulation index of 2. The precursor frequency of allopeptide reactive T cells was determined by limiting dilution analysis.ResultsLymphocytes from 82% of patients who were mismatched for at least one of the three DR molecules and had chronic allograft dysfunction specifically proliferated to the mismatched allopeptides (n=11). Proliferation was seen in only 6% of control subjects (2/33,P<0.0001). The proliferative response was low grade and was best detected on day 7-8 of culture in vitro. The precursor frequency of peptide-specific T cells was more than 10-fold higher compared with controls (P<0.001).ConclusionsThese data demonstrate for the first time that T cells of patients with chronic graft dysfunction are primed to recognize and respond to specific donor-derived major histocompatibility complex allopeptides. Our results support the hypothesis that T cells primed via the indirect pathway of allorecognition may be important mediators of chronic rejection and provide the rationale to develop specific therapeutic strategies to prevent or interrupt this process.

ISSN:0041-1337    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

BackgroundPlatelets are known to play an important role in the pathogenesis of adult respiratory distress syndrome as well as preservation-reperfusion injury of liver allografts. However, the role of platelets in pulmonary preservation-reperfusion injury is unknown. In this study, we examined whether the extent of platelet accumulation in the preserved and subsequently reperfused lungs correlated with the degree of preservation-reperfusion injury in a rat lung isotransplant model.MethodsHeart-lung blocks from donor rats were flushed with and preserved in modified Euro-Collins solution at 4°C for 0 hr (n=5), 6 hr (n=6), and 24 hr (n=6). The left lung was divided from the heart-lung block, transplanted into the recipient rat, and reperfused for 1 hr. Lung injury was evaluated by the left-to-right pulmonary blood flow ratio, the weight gain of the isograft, and the scores for histological categories of lung injury (intra-alveolar edema, intra-alveolar hemorrhage, and capillary congestion). Small portions of the lung isograft were excised and stained with an antibody specific for rat platelets. A scoring system was developed to semiquantitate the intensity of antibody staining in isografts.ResultsLung isografts were injured and platelets accumulated in the capillaries in proportion to the length of preservation endured before transplantation. The extent of platelet accumulation evaluated by our morphological scoring system correlated significantly with the degree of lung injury assessed by the blood flow ratio (P<0.001), the weight gain (P<0.001), and the histological scores for intra-alveolar hemorrhage (P<0.05) and for capillary congestion (P<0.001).ConclusionsThe results of this study suggest that platelet accumulation is a potential factor responsible for preservation-reperfusion injury of lung isografts in the rat.

ISSN:0041-1337    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

BackgroundExperiments were designed to evaluate the effect of treatment with an inhibitor of lipid peroxidation, H 290/51, on the interaction of lymphocytes and pulmonary arteries during acute lung rejection. It was hypothesized that inhibition of lipid peroxidation would reduce contractions of the pulmonary arteries to autogenous rejection-activated lymphocytes.MethodsSingle-lung transplantation was performed in three groups of dogs: group 1 was maintained on immunosuppression for 8 days postoperatively; in group 2, immunosuppression was discontinued on postoperative day 5, so that rejection occurred on postoperative day 8; in group 3, immunosuppression was discontinued after 5 days, and the lipid peroxidation inhibitor H 290/51 was given orally for 3 days. The pulmonary arteries were removed, cut into rings, and suspended in organ chambers for measurement of isometric force.ResultsMacrophage-depleted mononuclear cells (MNCs; lymphocytes) isolated from blood caused cell number-dependent contractions in rings of the pulmonary arteries from all dogs. In the rejecting dogs treated with H 290/51 (group 3), contractions to MNCs were significantly greater in rings without endothelium compared to rings with endothelium. Contractions to MNCs with or without endothelium were reduced by adding deteroxamine to the medium but not by adding superoxide dismutase and catalase.ConclusionsThe results of this study show that treatment with a lipid peroxidation inhibitor, H 290/51, does not prevent acute rejection of transplanted lungs. The treatment with the peroxidation inhibitor modifies contractions of the pulmonary arteries in response to rejection-activated lymphocytes, indicating that reactive oxidative metabolites may be involved in the vasoactive response resulting from this interaction.

ISSN:0041-1337    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

BackgroundOur goal was to study physiologic responses of human T lymphocytes to OKT3 in the human peripheral blood lymphocyte-severe combined immunodeficiency (hu-PBL-SCID) mouse model.MethodsSCID mice were pretreated with anti-asialo-GM1 (α-ASGM1) and radiation, then engrafted with human peripheral blood lymphocytes (PBLs). Seven to 14 days after engraftment, when most human T cells in the spleen of these mice are CD3+/CD4+and CD3+/CD8+, mice were treated with OKT3 or control antibody. Mice were killed for histopathologic examination, for flow cytometric assessment of the engrafted human lymphocytes, and for analysis of human tumor necrosis factor-α serum levels.ResultsIntravenous injection of 5 μg of OKT3 resulted in early antigenic modulation of engrafted human T lymphocytes, with the emergence of CD3-/CD4+and CD3-/CD8+cells in the spleen of hu-PBL-SCID mice. There was an increase in the serum concentration of human tumor necrosis factor-α within 4 hr after OKT3 injection, suggesting early T-cell activation. Antigenic modulation and activation of the human lymphocytes in the spleen was followed by their depletion within 24 hr. This human T-cell response to OKT3 in hu-PBL-SCID mice is analogous to the response in humans treated with OKT3 and in BALB/c mice injected with an anti-murine CD3 monoclonal antibody. Graft-versus-host disease in the mice was abrograted by OKT3 treatment, and OKT3-treated mice lived longer than controls. Histopathologic studies showed clearance of lymphocytic infiltration in the liver and lungs of OKT3-treated mice.ConclusionsThese findings provide further evidence of functional human immune T cells in the hu-PBL-SCID mouse. This model may have useful applications in the study of transplantation immunology.

ISSN:0041-1337    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

BackgroundSuccessful clinical application of hepatocyte transplantation has been limited by poor engraftment of the recipient liver by transplanted hepatocytes.MethodsTo address the hypothesis that liver regeneration induced by an acute hepatotoxic injury promotes expansion of transplanted hepatocytes, we injected β-galactosidase-labeled hepatocytes intrasplentically into mice 24 hr after treatment with carbon tetrachloride (CCl4) and into untreated controls.ResultsMacroscopic examination of whole liver segments identified clusters of transplanted hepatocytes uniformly spread on the capsular surface of the recipient liver and in the liver core following the distribution pattern of portal vein branches. Frozen sections showed that although the degree of initial engraftment of transplanted hepatocytes was similar in CCl4-treated and control livers, there was a fourfold increase of engrafted hepatocytes in CCl4-treated livers 10 days after transplantation which persisted to 28 days.ConclusionsWe conclude that the number of transplanted hepatocytes increases in response to regeneration signal triggered by an acute hepatocyte-specific liver injury.

ISSN:0041-1337    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

BackgroundThis study was conducted to determine whether the duration of total hepatic ischemia influences reticuloendothelial phagocytic activity and tumor necrosis factor (TNF)-α production after reperfusion.MethodsMale rats pretreated with either normal saline (NS group) or gadolinium chloride (7 mg/kg) for 2 days to inhibit Kupffer cell function (GC group) were subjected to 30, 60, or 90 min of total hepatic ischemia.ResultsThe animals tolerated hepatic ischemia well for 30 and 60 min. Although the 7-day survival rate of the NS group decreased to 28% after 90 min of hepatic ischemia, that of the GC group improved significantly to 68% (P<0.01). In the NS group, plasma alanine transaminase and TNF-α levels after reperfusion increased with the length of hepatic ischemia. The phagocytic index (PI) after 60 min of reperfusion following 90 min of hepatic ischemia showed significant depression compared with the preischemic level and the value after 30 or 60 min of ischemia. The GC group had significantly lower plasma alanine transaminase and TNF-α levels as well as significantly less polymorphonuclear leukocyte infiltration in the liver compared with the NS group. The preischemic PI was significantly inhibited in the GC group when compared with that in the NS group, but PI in the GC group did not change significantly after reperfusion, irrespective of the ischemic time.ConclusionsThis study demonstrated that warm ischemia of up to 60 min is tolerable for normal rat liver without a detrimental effect on phagocytic activity. Modulation of Kupffer cell function may have the potential to prevent reperfusion injury after hepatic ischemia, which may allow safe prolongation of the ischemic time.

ISSN:0041-1337    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

BackgroundAlthough HLA identity between donor and recipient is no longer an absolute requirement for bone marrow transplantation, knowledge of the degree of HLA compatibility is necessary for determining the induction and immunosuppression regimen to be used. In cases of related donor transplantation, HLA compatibility may be assessed by defining the HLA phenotypes at the allele level using high-resolution, DNA-based typing methods or by determining the genotypes of the patient and potential donor from the HLA phenotypes, ascertained by low-resolution typing, of their family members.MethodsWe developed an algorithm that can be used to assess the relative costs of these two approaches. We applied population frequencies for HLA-DR alleles to this algorithm to determine at what cost per test ratio for high-resolution:low-resolution testing the costs of the two approaches are equal.ResultsIn transplants involving a sibling pair who have the same HLA-A, -B, and -DR antigens, these values are 1.16-1.83 for African-Americans and 1.23-1.97 for Caucasians, depending on the relatives available for testing. With a slight increase in the resolution level achieved with DR antigen testing, the range of values becomes 1.10-1.74. We also estimated that the probability that two antigenically identical siblings have identical HLA-DRB1 alleles is >99% for both African-Americans and Caucasians. A review of 615 cases from our transplant program showed that all of 192 pairs of antigenically identical patients and sibling donors were genotypically or allelically identical, indicating that this estimate is valid.ConclusionsTransplant programs can apply these algorithms to determine the most cost-effective scheme for histocompatibility testing.

ISSN:0041-1337    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

BackgroundDespite the current level of sophistication of molecular typing for class I and class II alleles, a significant proportion (20-40%) of recipients of HLA-identical sibling marrow develop severe, acute graftversus-host disease (GVHD) after bone marrow transplantation. It has been suggested that the frequency of patient-specific helper T lymphocyte precursors (HTLp) detected in the HLA-identical sibling donor correlates with the incidence and severity of acute GVHD after transplantation.MethodsThis study group consisted of 42 patients who all received bone marrow from HLA-identical sibling donors from January 1990 to December 1996. Using a limiting dilution analysis, donor HTLp frequencies were determined on samples collected before transplantation. The HTLp assay used the cytotoxic T-cell line, CTLL-2, which proliferates in the presence of interleukin-2. The reliability and reproducibility of this assay was established by using cryopreserved batches of CTLL-2 cells of known sensitivity.ResultsThe recipient-directed HTLp frequencies detected in the donor before transplantation were correlated with the incidence and severity of acute GVHD experienced by the recipient after transplantation. Statistical analysis revealed an extremely significant correlation between donor precursor frequencies and the development of acute GVHD in the patient after transplantation (P<0.0001).ConclusionsThis study suggests that together with molecular typing the HTLp frequency should be considered when selecting the most suitable sibling donor for bone marrow transplantation.

ISSN:0041-1337    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

BackgroundAllograft rejection is mediated by T cells that recognize allogeneic major histocompatibility complex (MHC) molecules via the direct and indirect pathway. The direct pathway involves T cells that react against MHC/peptide complexes expressed on the surface of donor antigen-presenting cells (APCs). In contrast, T cells involved in the indirect pathway recognize peptides derived from processing and presentation of allogeneic MHC molecules by self (recipient) APCs. To explore the relative contribution of these two pathways to rejection, we have evaluated the response of peripheral blood T cells from 50 heart transplant recipients against donor APCs (direct recognition) and against self APCs pulsed with synthetic peptides corresponding to the hypervariable region of the mismatched HLA-DR antigens of the donor (indirect recognition).MethodsT cell reactivity against donor APCs was quantitated by measuring the expression of CD69 on allostimulated CD3+LDA1+cells. Reactivity to synthetic allopeptides was determined in limited dilution assays.ResultsSerial studies of the kinetics of direct and indirect recognition showed that both pathways contribute to early acute rejection episodes. Primary rejection was accompanied invariably by indirect recognition of a dominant allopeptide. Intermolecular spreading of T cell epitopes was observed during recurrent rejections. Enhanced recognition of donor alloantigens via the direct pathway was found predominantly during early rejection episodes. A single form of allorecognition was shown to occur in some rejection episodes.ConclusionsMonitoring of the direct and indirect pathway of allorecognition provides a reliable method for prediction and differential diagnosis of acute rejection of heart allografts.

ISSN:0041-1337    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

BackgroundPosttransplant lymphoproliferative disorder (PTLD) has been observed with increasing frequency consequent to the availability of more effective and potent immunosuppression. Prior work suggested that a peripheral blood monitoring strategy detecting peripheral B lymphoproliferation was effective in the early diagnosis of PTLD among 7 of 179 (3.9%) consecutive transplant recipients. Each of those seven patients received at least one course of antithymocyte globulin, Minnesota antilymphocyte globulin, or OKT3 before developing PTLD.MethodsTo determine whether antiviral prophylaxis might reduce the incidence of PTLD, a subsequent group of 198 consecutive recipients received either ganciclovir or acyclovir during antilymphocyte antibody administration. When the donor or recipient were cytomegalovirus-seropositive, ganciclovir was given; acyclovir was used when both were cytomegalovirus-seronegative. Baseline and protocol posttransplant cell surface profiles were obtained using immunofluorescence and flow cytometry to detect T cells, lymphocyte activation markers, and the CD19 B cell antigen.ResultsDemographic factors, including the incidence of recipients more than 50 years of age, non-Caucasians, previous transplantation, and diabetes mellitus, were similar in both groups. Additionally, the number of patients receiving antilymphocyte preparations was similar. However, only one patient (0.5%) from the latter group who received preemptive antiviral therapy developed PTLD. Although elevations in CD19+B cells preceded clinical PTLD among each of the seven earlier patients, evidence of peripheral B cell proliferation was not demonstrated for the sole patient from the latter group, which suggests a possible effect of antiviral therapy.ConclusionsProphylactic antiviral therapy may reduce the sensitivity of peripheral monitoring for B lymphoproliferation, but the dramatic reduction in PTLD incidence strongly supports its use among transplant recipients at risk.

ISSN:0041-1337    

出版商:OVID    

年代:1997

数据来源: OVID