The application of TCR transgenic mice to transplantation immunology is hampered by the limited lines available. Recently, we reported CD4+ T cell receptor (TCR) transgenic mice specific for I‐Abm12 ...expressed on B6.C.H‐2bm12 mice. Here, we characterized rejection of skin and vascularized cardiac allografts in these mice, which we term ABM (for anti‐bm12). In vivo proliferative experiments reveal that all CD4 T cells in ABM mice react to bm12 antigens. Surprisingly, while ABM mice have accelerated (compared to B6 recipients) rejection of bm12 skin allografts, they, like B6 recipients, fail to acutely reject bm12 cardiac allografts. This is not due to lack of immunogenicity of bm12 hearts, as these grafts are acutely rejected by primed ABM recipients, although not by primed B6 recipients. Lastly, long‐term surviving bm12 grafts in ABM recipients are relatively free from chronic rejection (compared with B6 recipients), which may be due to skewing of the CD4 repertoire towards direct alloreactivity, and consequent lack of CD4 mediated indirect allorecognition as evidenced by the lack of IgG deposition in those grafts. The results indicate that a complex interplay between responder frequency, priming and repertoire dictates the occurrence, or lack thereof, of acute and chronic rejection.
Inducible costimulatory molecule (ICOS) plays a pivotal role in T cell activation and Th1/Th2 differentiation. ICOS blockade has disparate effects on immune responses depending on the timing of ...blockade. Its role in transplantation immunity, however, remains incompletely defined. We used a vascularized mouse cardiac allograft model to explore the role of ICOS signaling at different time points after transplantation, targeting immune initiation (early blockade) or the immune effector phase (delayed blockade). In major histocompatibility-mismatched recipients, ICOS blockade prolonged allograft survival using both protocols but did so more effectively in the delayed-treatment group. By contrast, in minor histocompatibility-mismatched recipients, early blockade accelerated rejection and delayed blockade prolonged graft survival. Alloreactive CD4+ T cell expansion and alloantibody production were suppressed in both treatment groups, whereas only delayed blockade resulted in suppression of effector CD8+ T cell generation. After delayed ICOS blockade, there was a diminished frequency of allospecific IL-10-producing cells and an increased frequency of both IFN-gamma- and IL-4-producing cells. The beneficial effects of ICOS blockade in regulating allograft rejection were seen in the absence of CD28 costimulation but required CD8+ cells, cytotoxic T lymphocyte antigen-4, and an intact signal transducer and activator of transcription-6 pathway. These data define the complex functions of the ICOS-B7h pathway in regulating alloimmune responses in vivo.
The Caroni River, a tributary of the Orinoco River in the State of Bolivar, Venezuela, has been subjected to mining since the end of the last century. Until the 1990s, hundreds of artisanal miners ...operated along a 70
km stretch of the river using rudimentary suction dredges to extract gold and diamonds from sediments. Although artisanal miners created considerable wealth along the river, the local community has also been negatively impacted by the social and environmental effects that characterize this sector. The flooding of many parts of the Lower Caroni River, in conjunction with the development of a large hydroelectric-power complex, changed the conditions for dredging operations.
A Canada-based company is proposing to open the recently-created hydro-electrical lakes to a Mineral Dredging Project. The early forecasting of potential socioeconomic and environmental impacts would be a valuable tool to build a sustainable business case that facilitates the integration of the project into a sensitive environment. These strategies, currently used in other economic sectors, would contribute to the identification of opportunities to negotiate mutually beneficial agreements with stakeholders of the Project, and reduce the risk of conflict, in this particular case, with the hydroelectric company (EDELCA), former small-scale miners and other stakeholders.
This paper, based on the pre-feasibility study of the Project, assesses the applicability of such tools to the mineral dredging and to junior mining company projects in general.
To determine the precise in vivo interaction between T-cell costimulatory blockade and conventional immunosuppression in transplantation.
Blocking B7 or CD154 T-cell costimulatory activation pathways ...prevents allograft rejection in small and large animal transplant models and is considered a promising strategy for clinical organ transplantation.
A fully MHC-mismatched vascularized mouse cardiac allograft model was used to test the interactions between anti-CD154 or CTLA4Ig monotherapy and conventional immunosuppressive drugs in promoting long-term graft acceptance. The frequency of alloreactive T cell was measured by ELISPOT. Chronic rejection was examined by histology.
Cyclosporine, tacrolimus, and anti-IL-2R monoclonal antibody therapy abrogated the effect of a single-dose protocol of anti-CD154 therapy. In contrast, rapamycin acted synergistically with anti-CD154 therapy in promoting long-term allograft survival. The addition of calcineurin inhibitors did not abolish this synergistic effect. Intense CD154-CD40 blockade by a multiple-dose schedule of anti-CD154 resulted in long-term graft survival and profound alloreactive T-cell unresponsiveness and overcame the opposite effects of calcineurin inhibitors. CTLA4Ig induced long-term graft survival, and the effect was not affected by the concomitant use of any immunosuppressive drugs.
The widespread view that calcineurin inhibitors abrogate the effects of T-cell costimulatory blockade should be revisited. Sufficient costimulatory blockade and synergy induced by CD154 blockade and rapamycin promote allograft tolerance and prevent chronic rejection.
The effectiveness of an encapsulated rumen-protected methionine compound (RPMet) for delivering methionine postruminally and its effect on plasma amino acid concentrations, milk production and milk ...composition were evaluated. Thirty multiparous Holstein cows in early lactation were randomly assigned to five levels of RPMet. RPMet was supplied at 0, 550, 1100, 1650 or 3300 mg/kg of concentrate resulting in an intake of 0, 6.9, 12.9, 19.6 or 40.2 g of supplemental DL-methionine/day for each cow. The basal diet was alfalfa-bromegrass hay and a 15.8% crude protein corn- and soybean meal-based concentrate mixture. The experiment was divided into pretreatment and treatment periods, each consisting of 21 days. Feed intake and milk production were measured daily, milk composition weekly and plasma amino acid concentrations twice daily on days 17 and 20 of the pretreatment period and on days 4, 10 and 21 of the treatment period. RPMet was effective in delivering methionine postruminally, which increased concentrations of methionine in plasma. Dry matter intake, milk production, milk composition and body weight were not significantly affected by RPMet.
Objective:
Mechanical circulatory support is an established therapy for patients with terminal heart failure either as a bridge to transplant or as chronic implant. A new pump generation minimizes ...these risks by implementation of magnetically levitated rotors and miniaturized size.
Methods:
We report on 7 patients implanted in our center from 03/2006 till 09/2007. Mean age of the 6 male and 1 female patients was 47±12yrs. The HeartWare HVAD is a miniaturized centrifugal pump, with a rotor levitated by hydraulic forces and permanent magnets. The small device size allows intrapericardial placement, which reduces surgical trauma and expedites the implant procedure.
Results:
The intraoperative course was uneventful in 6 patients and all were extubated on the same day of implantation. One patient experienced postoperative severe pulmonary dysfunction with right heart failure and required temporary RVAD support. Another patient died from fulminant septicemia on postop day 7. The mean VAD flow ranged from 4,0–6,5l/min. Two patients were successfully transplanted after 426 and 349 days. Four patients remain supported with a mean of 207±173 days. After 6 months, one patient experienced a urinary tract infection, temporary hemolysis and was successfully transplanted 4 months later. The two most recent patients remain hospitalized.
Conclusion:
This new miniaturized pump allows a fast and less invasive implantation and proves in this preliminary cohort of patients satisfactory long-term results with excellent quality of life. These promising preliminary results of the system will considerably widen the indications for this therapy.
Within the last decade implantation of a left ventricular assist device (LVAD) became an established procedure for patients with deteriorating end-stage heart failure.
Methods:
From November 1998 ...untill September 2006 sixtythree patients with terminal end-stage heart failure received a MicroMed DeBakey LVAD as a bridge to transplantation in our institution. Mean age of the 51 male and 12 female patients was 52±12 years (range 15–66). Main underlaying disease was idiopathic cardiomyopathy in 32 cases, followed by ischemic cardiomyopathy in 25 cases. Anticoagulation was based on iv heparin and oral phenprocoumon and antiaggregation with adjusted doses of Aspirin.
Results:
Mean duration on pump for all patients was 124±88 days, with a total of 5556 patient days. Thirteen patients were supported longer than 180 days, with longest duration of 321 days. Thirtyone patients were successfully transplanted after a mean pump support of 146±61 days. A total of 42 patients (66.7%) were successfully transplanted, or survived longer than 180 days on support, or are still on support with a mean duration of 148±79 days. Four patients experienced right heart failure and received a temporary RVAD. 9 patients (14.2%) died of a CVA, 12 patients (19%) died with MOF.
Conclusion:
Miniaturized axial flow pumps like the MicroMed DeBakey LVAD demonstrated in a larger single center application support properties comparable to historical results from first generation pulsatile pumps
The mechanisms underlying physiological regulation of alloimmune responses remain poorly defined. We investigated the roles of cytokines, CTLA-4, CD25(+) T cells, and apoptosis in regulating ...alloimmune responses in vivo. Two murine cardiac transplant models were used, B10.D2 (minor mismatch) and C57BL/6 (major mismatch), into BALB/c recipients. Recipients were wild type, STAT4(-/-) (Th1 deficient), or STAT6(-/-) (Th2 deficient) mice. Minor mismatched allografts were accepted spontaneously in approximately 70% of wild type and STAT4(-/-) mice. By contrast, there was significantly shorter graft survival in minor mismatched STAT6(-/-) mice. Either the adoptive transfer of STAT4(-/-) splenocytes or the administration of IL-4Fc fusion protein into STAT6(-/-) mice resulted in long term graft survival. Blocking CTLA-4 signaling accelerated the rejection in all recipients, but was more pronounced in the minor combination. This was accompanied by an increased frequency of alloreactive T cells. Furthermore, CTLA-4 blockade regulated CD4(+) or CD8(+) as well as Th1 or Th2 alloreactive T cells. Finally, while anti-CD25 treatment prolonged graft survival in the major mismatched combination, the same treatment accelerated graft rejection in the minor mismatched group. The latter was associated with an increased frequency of alloreactive T cells and inhibition of T cell apoptosis. These data demonstrate that cytokine regulation, CTLA-4 negative signaling, and T cell apoptosis play critical roles in regulating alloimmunity, especially under conditions where the alloreactive T cell clone size is relatively small.
Objective:
Left ventricular assist device (LVAD) implantation is an effective treatment option to bridge patients with end-stage heart failure to transplantation. Continuous flow devices that provide ...non- or low-pulsatile mechanical circulatory support are increasingly used.
Methods:
From November 1998 to September 2007, 89 patients underwent implantation of continuous flow LVADs as bridge to transplantation. This included 77 (86.5%) MicroMed DeBakey, 7 (7.9%) HeartWare and 5 (5.6%) Duraheart LVADs.
Results:
Mean age was 52.3±11.5 years, 85.4% were male, and ischemic heart disease was the cause of heart failure in 43.8%. Mean glomerular filtration rate (GFR) was 62.0±20.5 mL/min/1.73 m2; 49.4% required inotropic support before LVAD implantation; 14.6% had undergone previous sternotomy. Urgent LVAD implantation was performed in 12.4%. Mean duration of support was 139.5±110.8 days. Post-LVAD survival was 92.0%, 76.3%, and 62.7% at 1, 3, and 6 months, respectively. Post-LVAD adverse events included occurrence of stroke (n=15, 16.9%), reoperation for bleeding (n=22, 24.7%), right heart failure requiring RVAD/ECMO support (n=6, 6.7%), and renal failure requiring hemofiltration (n=30, 33.7%). Post-LVAD causes of death included sepsis (n=13, 38.2%), multi-organ failure (n=9, 26.5%), and cerebrovascular events (n=10, 29.4%). Bridge-to-transplant rate was 50.6%, with 10 (11.2%) patients currently on device. Post-transplant 1-, 3-, and 5- year survival was 87.8%, 78.8%, and 72.3%, respectively.
Conclusion:
Our results with 3 continuous flow LVADS represent successful bridging to transplantation and post-transplant survival in end-stage heart failure patients.
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