Healing of high-porosity polytetrafluoroethylene arterial grafts is influenced by the nature of the surrounding tissue.

The aim of this study was to determine the influence of the nature of the perigraft tissue in the healing pattern of high-porosity polytetrafluoroethylene (PTFE) vascular grafts. Nine-centimeter long segments of unreinforced experimental high-porosity (60 microns) PTFE grafts were placed as abdominal aortic interposition in mongrel dogs. Three grafts served as controls (group A); in five dogs (group B) a 25 x 25 cm piece of devascularized omentum was wrapped around the graft. In five dogs (group C) the omentum with its own vascular supply was completely wrapped around the graft. Animals were killed 4 weeks after surgery. The percentage of thrombus-free area was 31% in group A grafts, 39% in group B grafts, and 79% in group C grafts (p less than 0.01). Scanning electron microscopy showed many confluent areas of endothelium-like cells in the midportion of group C grafts, corresponding to capillary ingrowth. Transmural endothelial migration was more evident in group C grafts. We conclude that the nature of the perigraft tissue influences transmural capillary migration and the endothelialization rate of high-porosity PTFE grafts in dogs. Agents able to increase capillary formation in the perigraft tissue might improve endothelialization of vascular grafts.     

Mechanism of action of donor-specific transfusion in inducing tolerance: role of donor MHC molecules, donor co-stimulatory molecules, and indirect antigen presentation

Donor-specific transfusion (DST) can synergize with T cell co-stimulatory blockade in inducing tolerance in several transplant models, but the mechanism of action of DST is poorly characterized. This study used genetically altered mice in an established model of cardiac transplantation to study the role of MHC and co-stimulatory molecule expression on DST cells in mediating the immunomodulatory effects of DST. In addition, to examine the role of indirect antigen presentation in the effect of DST, experiments used recipient mice that do not express MHC class II molecules on peripheral antigen-presenting cells, but do have functional CD4(+) T cells (II(-)4(+)). As previously reported, treatment with DST from wild-type donors in combination with CD154 blockade induced tolerance in wild-type recipients of cardiac allografts. Tolerance in this model is also induced despite the absence of MHC class I and II, CD40, or B7 molecules on transfused cells. In contrast, eliminating the indirect pathway using II(-)4(+) recipients blocked the induction of long-term cardiac allograft survival by DST. These results indicate that the indirect antigen recognition pathway mediates the immunomodulatory effect of DST in inducing transplantation tolerance in vivo.     

Effect of blood transfusion on antigen presentation function and on interleukin 2 generation

To study the effect of blood transfusion (BT) on cell-mediated immunity, we examined the antigen presentation function of peritoneal macrophages and interleukin 2 (IL-2) generation by splenocytes. C3H/HEJ mice were transfused with 0.2 mL of fresh allogeneic blood obtained from C57BL/6 mice; they were killed on days 1, 3, and 7 after BT. A second group of C3H/HEJ mice was transfused with 0.2 mL/d of the same allogeneic blood on three successive days; they were killed on day 7 following the last BT. The antigen presentation function of peritoneal macrophages was measured by utilizing a D10.G4.1 T-helper cell clone; IL-2 activity in supernatants of concanavalin A-stimulated splenocytes was tested by utilizing an IL-2-dependent HT-2 cell line. The results indicate that although antigen presentation function remains unaffected after single and multiple BTs, the ability of splenocytes to generate IL-2 decreases significantly even after a single BT. Thus, the increased susceptibility to infection and the additional immune perturbations in malignant neoplasms following BT may be due in part to decreased IL-2 generation.     

Insulin's anabolic effect is influenced by route of administration of nutrients

OBJECTIVE: To determine if the anabolic effects of intravenous insulin on protein kinetics could be exploited in the enterally fed trauma victim. DESIGN: Randomized, crossover control protocol. SETTING: Level I trauma center. PATIENTS: Ten trauma patients with an Injury Severity Score higher than 20. Exclusion criteria included diabetes mellitus, pregnancy, steroid use, and aged younger than 18 years or older than 65 years. INTERVENTIONS: Within the first 24 hours of admission to the intensive care unit, each patient had a transpyloric feeding tube inserted radiographically. Enteral nutrition was provided with a protein supplement (Ensure, Ross Laboratories, Columbus, Ohio) and Promod, supplemented with protein powder to supply 1.5 g/kg per day of protein and 156.9 kJ/kg per day. Intravenous insulin was provided at 0.043 U/kg per hour beginning on the second or fourth day. MAIN OUTCOME MEASURES: Urinary nitrogen balance and 3-methylhistidine excretion rates were measured at the end of the third and fifth days. Plasma glucose, insulin, and C-peptide levels were obtained at these same times. RESULTS: Urinary nitrogen balance was not significantly different with or without the administration of insulin (-4.58+/-50.1 mg/kg per day vs -9.38+/-50.9 mg/kg per day, respectively). 3-Methylhistidine excretion rates did not change significantly with or without the administration of insulin (5.77+/-0.67 micromol/kg per day vs 6.15+/-0.43 micromol/kg per day, respectively). Serum insulin levels did not differ significantly when exogenous infusions were added (57.8+/-17.9 microU/mL vs 82.1+/-44.9 microU/mL), but serum C-peptide levels did decrease significantly when exogenous insulin was added (5.11+/-3.2 microU/mL vs 10.28+/-3.5 microU/mL; P = .04). Serum glucose levels decreased significantly when insulin was administered (5.8+/-0.4 mmol/L [104.6+/-7.2 mg/dL] vs 7.7+/-0.4 mmol/L [138.1+/-7.4 mg/dL; P =.004). CONCLUSION: The anabolic effect of intravenous insulin on protein kinetics is not evident when nutrition is provided enterally in the trauma victim.     

MHC class II-mediated antigen presentation by alloreactive rat CD4+ T cells does not induce regulatory properties

Activated CD4+ T cells have the capacity to express major histocompatibility complex (MHC) class II molecules and to present processed antigens to T cells. Because the role of MHC class II positive T cells in allograft rejection is unknown, the purpose of this study was to investigate their function as antigen-presenting cells (APCs) in the allogeneic immune response. For this, alloreactive CD4+ T cells were induced in Lewis rats by immunization with the allogeneic peptide P1. The P1-specific T cells are involved in the rejection of allografts from Wistar Furth rats. With monoclonal antibodies specific for the αβ T-cell receptor (clone R73) and MHC class II molecules (clone Ox6), the presence of antigen-specific T cells, with and without expression of MHC class II molecules, was demonstrated. Concerning their ability to bind these antibodies they were characterized as R73^pos, Ox6^pos and R73^pos, Ox6^neg, respectively. The R73^pos, Ox6^pos T cells loaded with P1 were indeed very effective in restimulating R73^pos, Ox6^neg T cells but not vice versa. Further on, R73^pos, Ox6^pos T cells, but not R73^pos, Ox6^neg T cells, were able to activate naïve allogeneic T cells demonstrating their capacity to express co-stimulatory molecules. In addition, specific mRNA for CD86, MHC class II, and CIITA, the master regulator of MHC class II expression, were detectable in the R73^pos, Ox6^pos T cells only. In conclusion, the R73^pos, Ox6^pos T cells act as professional APCs with the possible biological capability of amplifying the local immune response to the allograft.     

The T-cell anergy induced by Leishmania amazonensis antigens is related with defective antigen presentation and apoptosis

Leishmania amazonensis is the main agent of diffuse cutaneous leishmaniasis, a disease associated with anergic immune responses. In this study we show that the crude antigen of Leishmania amazonensis (LaAg) but not L. braziliensis promastigotes (LbAg) contains substances that suppress mitogenic and spontaneous proliferative responses of T cells. The suppressive substances in LaAg are thermoresistant (100 degrees C/1h) and partially dependent on protease activity. T cell anergy was not due to a decreased production of growth factors as it was not reverted by addition of exogenous IL-2, IL-4, IFN-gamma or IL-12. LaAg did not inhibit anti-CD3-induced T cell activation, suggesting that anergy was due to a defect in antigen presentation. It was also not due to cell necrosis, but was accompanied by expressive DNA fragmentation in lymph node cells, indicative of apoptosis. Although pre-incubation of macrophages with LaAg prevented their capacity to present antigens, this effect was not due to apoptosis of the former. These results suggest that the T cell anergy found in diffuse leishmaniasis may be the result of parasite antigen-driven apoptosis of those cells following defective antigen presentation.     

A major role for host MHC class I antigen presentation for promoting islet allograft survival

The purpose of this study was to determine the role for CD8 T cells versus generalized MHC class I-restricted antigen presentation in islet allograft rejection and tolerance. Diabetic C57BI/6 (B6, H-2(b)) controls, C57BI/6 CD8-deficient (CD8 KO), or MHC class I-deficient C57BI/6 (beta 2m KO) recipients were grafted with allogeneic BALB/c (H-2(d)) islets. Islet allografts were acutely rejected in untreated B6, CD8 KO, and in beta 2m KO mice, indicating that neither CD8 T cells nor host MHC class I is required for allograft rejection. We then determined the efficacy of costimulation blockade in these same strains. Costimulation blockade with anti-CD154 therapy facilitated long-term islet allograft survival in both B6 and in CD8 KO recipients. However, anti-CD154 treated beta 2m KO recipients were completely refractory to anti-CD154 therapy; all treated animals acutely rejected islet allografts with or without therapy. Also, anti-NK1.1 treatment of wild-type B6 mice abrogated graft prolongation following anti-CD154 therapy. Taken together, results show a dramatic distinction between two forms of MHC class I-restricted pathways in allograft prolongation. Although anti-CD154-induced allograft survival was CD8 T-cell independent, an intact host MHC class I-restricted (beta 2m-dependent) pathway is nevertheless necessary for allograft survival. This pathway required NK1.1+ cells, implicating NK and/or NKT cells in promoting allograft prolongation in vivo.     

增强抗原呈递功能的树突状细胞疫苗

树突状细胞（DC）疫苗的研究已成为当前肿瘤免疫治疗的一大热点。随着对DC的不断认识,其强大的功能可塑性为发展增强其抗原呈递功能的DC疫苗提供了新思路,现就DC疫苗增强其抗原呈递功能的种种途径进行综述。     

The delay of gastric emptying induced by remifentanil is not influenced by posture

Posture has an effect on gastric emptying. In this study, we investigated whether posture influences the delay in gastric emptying induced by opioid analgesics. Ten healthy male subjects underwent 4 gastric emptying studies with the acetaminophen method. On two occasions the subjects were given a continuous infusion of remifentanil (0.2 microg. kg(-1). min(-1)) while lying either on the right lateral side in a 20 degrees head-up position or on the left lateral side in a 20 degrees head-down position. On two other occasions no infusion was given, and the subjects were studied lying in the two positions. When remifentanil was given, there were no significant differences between the two postures in maximal acetaminophen concentration (right side, 34 micromol. L(-1); versus left side, 16 micromol. L(-1)), time taken to reach the maximal concentration (94 versus 109 min), or area under the serum acetaminophen concentration time curve from 0 to 60 min (962 versus 197 min. micromol. L(-1)). In the control situation, there were differences between the postures in maximal acetaminophen concentration (138 versus 94 micromol. L(-1); P < 0.0001) and area under the serum acetaminophen concentration time curves from 0 to 60 min (5092 versus 3793 min. micromol. L(-1); P < 0.0001), but there was no significant difference in time taken to reach the maximal concentration (25 versus 47 min). Compared with the control situation, remifentanil delayed gastric emptying in both postures. We conclude that remifentanil delays gastric emptying and that this delay is not influenced by posture.     

Prognostic role of carcinoembryonic antigen is influenced by microsatellite instability genotype and stage in locally advanced colorectal cancers

Background  

Carcinoembryonic antigen (CEA) is the most frequently used marker for colorectal cancer (CRC). Influence of genetic instability on tumor marker expression is not known. The aim of this study was to investigate microsatellite instability (MSI) of CEA serum levels in locally advanced CRC.     

The course of bone healing is influenced by the initial shear fixation stability.

Fracture healing is influenced by fixation stability and experimental evidence suggests that the initial mechanical conditions may determine the healing outcome. We hypothesised that mechanical conditions influence not only the healing outcome, but also the early phase of fracture healing. Additionally, it was hypothesised that decreased fixation stability characterised by an increased shear interfragmentary movement results in a delay in healing. Sixty-four sheep underwent a mid-shaft tibial osteotomy which was treated with either a rigid or a semi-rigid external fixator. Animals were sacrificed at 2, 3, 6 and 9 weeks postoperatively and the fracture callus was analysed using radiological, biomechanical and histological techniques. The tibia treated with semi-rigid fixation showed inferior callus stiffness and quality after 6 weeks. At 9 weeks, the calluses were no longer distinguishable in their mechanical competence. The calluses at 9 weeks produced under rigid fixation were smaller and consisted of a reduced fibrous tissue component. These results demonstrate that the callus formation over the course of healing differed both morphologically and in the rate of development. In this study, we provide evidence that the course of healing is influenced by the initial fixation stability. The semi-rigid fixator did not result in delayed healing, but a less optimal healing path was taken. An upper limit of stability required for successful healing remains unknown, however a limit by which healing is less optimal has been determined.     

The effects of tissue-associated and MHC class II antigen presentation on in vitro lymphoproliferative responses against canine liver and kidney cell subpopulations.

Purified hepatocytes (LH), Kupffer cells (LKu), and intrahepatic biliary duct cells (LD) were isolated from canine livers, as well as tubular cells from canine kidneys, by enzymatic digestion, gradient centrifugation, and tissue culture techniques. Incubation of LH, LKu, and LD for 48 hr in a two-compartment diffusion chamber opposite two-way mixed lymphocyte cultures, or with canine gamma interferon purified and standardized in our laboratory, resulted in a significant increase in class II expression. This was detected in the cell analyzer with directly fluoresceinated B1F6, a monoclonal antibody (mab) generated in our laboratory vs. a canine class II monomorphic epitope. An amplification of the allogeneic mixed lymphocyte liver cell cultures (MLLC) of at least 2-fold was observed by preinduction of canine class II expression with IFN-gamma on LKu and LD cells, but an autologous reaction could not be elicited. However, an autologous as well as allogeneic lymphoproliferation against kidney tubular cells (MLKC) could be easily observed without IFN-gamma and amplified with IFN-gamma to stimulation indices of at least 3 times that of noninduced cultures. Dependence of the allogeneic MLLC and allogeneic and autologous MLKC on class II gene expression was also evidenced by blocking of 3H-thymidine uptake seen by incubation with 5 micrograms of B1F6. Another mab, I1F6, generated against tubular cells and inhibiting the autologous and allogeneic MLKC, had no blocking effect on lymphoproliferation with any of the liver cell preparations. No such tissue-specific mab (analogous to I1F6) has thus far been found in response to mouse immunization with LH, LKu, or LD. In the absence of accepted defined molecular probes in the dog as yet, we conclude that, in contrast to kidney tubular cells, cells of the normal canine liver do not readily stimulate a primary lymphoproliferative autoimmune reaction in vitro despite class II amplification. Thus autoreactivity (as opposed to alloreactivity) is much less prominent in immune recognition of purified cellular components of nondiseased liver tissue than of kidney tissue in which tissue-associated epitopes are more operative.