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C F Barker

Publications and source records attributed to C F Barker.

At least 37 records · Page 2Linked to original sources
PubMed1999

A direct method for the calculation of alloreactive CD4+ T cell precursor frequency.

BACKGROUND: Direct measurement of the precursor frequency of alloreactive CD4+ T cells has been impossible due to the lack of a specific means of determining the absolute number of daughter cells generated with each division in a repertoire of stimulated T cells. METHODS: Responder lymphocytes were fluorescently labeled and adoptively transferred into irradiated allogeneic stimulator mice or incubated in vitro with irradiated stimulator splenocytes. After a 65- to 70-hr stimulation period, responder cells were analyzed by flow cytometry. RESULTS: The precursor frequency of dividing CD4+ T cells was determined both in vivo and in vitro. The observed number of alloreactive daughter cells generated with each round of division was used to calculate the frequency of alloantigen-specific CD4+ T cells. CONCLUSIONS: A novel method for the direct calculation of the frequency of alloreactive CD4+ T cells is described. This technique allows the determination of changes in the frequency of alloreactive T cells that might underlie tolerance to alloantigens.

Animals↗
PubMed1999

Cutting edge: alloimmune responses against major and minor histocompatibility antigens: distinct division kinetics and requirement for CD28 costimulation.

Comparative study of alloimmune responses against major and minor histocompatibility Ags has been limited by the lack of suitable assays. Here, we use a bioassay that permits tracking of alloreactive CD4+ T cell populations as they proliferate in response to major or minor histocompatibility Ags in vivo. Division of alloreactive CD4+ T cells proceeded more rapidly in response to major histocompatibility Ags than minor Ags, although CD4+ T cells alloreactive to minor Ags had a similar capacity to divide successively up to eight times after stimulation. Allorecognition of minor histocompatibility Ags was highly dependent on CD28 costimulation, with the frequency of CD4+ T cells proliferating in response to minor Ags in the absence of CD28 costimulation reduced up to 20-fold. These findings highlight differences in signaling processes that lead to allorecognition of major and minor histocompatibility Ags and have implications on the design of interventions aimed at abrogating these responses.

Animals↗
PubMed1999

Perigraft air, fever, and leukocytosis after endovascular repair of abdominal aortic aneurysms.

BACKGROUND: The postimplantation syndrome of fever and leukocytosis after endovascular repair of infrarenal aortic aneurysms has not been previously characterized and its etiology is not known. METHODS: We studied the first 12 patients who underwent successful endovascular repair of infrarenal aortic aneurysms with Dacron-covered stent-grafts, as part of an ongoing phase II clinical trial. Sepsis syndrome evaluations (physical examination, urinalysis, chest radiograph, urine cultures, and blood cultures) were performed for all patients with postoperative temperature (T) greater than 101.4 degrees F. Computed tomography scans of the abdomen were performed, as part of the clinical protocol, on postoperative days 2 and 30. RESULTS: Fever (T > 101.4 degrees F) was seen in 8 of 12 (67%) patients (P < 05). An additional 2 of 12 (17%) patients had low-grade fevers (100.3 degrees F, 100.6 degrees F). Only 2 of 12 (17%) patients remained afebrile postoperatively. Leukocytosis with counts over 11,000 white blood cells (WBC)/dL was observed in 7 of 12 (58%) patients (P < 05). Sepsis evaluations failed to identify any source of infection in 11 of 12 (97%) patients. Computed tomography scan evidence of perigraft air was noted in 8 of 12 (67%) patients. All patients were afebrile, had normal white blood cell counts, and were discharged within 1 week postoperatively. There has been no evidence of graft infection after 1 to 6 months of follow-up. CONCLUSIONS: Fever and leukocytosis after stent-graft repair of aortic aneurysms does not represent evidence of systemic or graft infection and is not clearly related to nonspecific causes of postoperative fever and leukocytosis. Moreover, the finding of early postoperative perigraft air is not necessarily an indication of graft infection even when concurrently present with fever and leukocytosis.

Air↗
PubMed1999

Prevention of autoimmune recurrence and rejection by adenovirus-mediated CTLA4Ig gene transfer to the pancreatic graft in BB rat.

Type 1 diabetes is the result of a selective destruction of pancreatic islets by autoreactive T-cells. Therefore, in the context of islet or pancreas transplantation, newly transplanted beta-cells are threatened by both recurrent autoimmune and alloimmune responses in recipients with type 1 diabetes. In the present study, using spontaneously diabetic BB rats, we demonstrate that whereas isolated islets are susceptible to autoimmune recurrence and rejection, pancreaticoduodenal grafts are resistant to these biological processes. This resistance is mediated by lymphohematopoietic cells transplanted with the graft, since inactivation of these passenger cells by irradiation uniformly rendered the pancreaticoduodenal grafts susceptible to recurrent autoimmunity. We further studied the impact of local immunomodulation on autoimmune recurrence and rejection by ex vivo adenovirus-mediated CTLA4Ig gene transfer to pancreaticoduodenal grafts. Syngeneic DR-BB pancreaticoduodenal grafts transduced with AdmCTLA4Ig were rescued from recurrent autoimmunity. In fully histoincompatible LEW-->BB transplants, in which rejection and recurrence should be able to act synergistically, AdmCTLA4Ig transduced LEW-pancreaticoduodenal allografts enjoyed markedly prolonged survival in diabetic BB recipients. In situ reverse transcription-polymerase chain reaction revealed that transferred CTLA4Ig gene was strongly expressed in both endocrine and exocrine tissues on day 3. These results indicate the potential utility of local CD28-B7 costimulatory blockade for prevention of alloimmune and autoimmune destruction of pancreatic grafts in type 1 diabetic hosts.

Abatacept↗
PubMed1998

Utility of adenoviral-mediated Fas ligand gene transfer to modulate islet allograft survival.

BACKGROUND: One of the best-defined mechanisms for the induction of apoptosis involves signaling via the cell surface molecule Fas, after binding of Fas ligand. Expression of Fas ligand is tightly regulated, being expressed primarily by T cells after activation, where it serves as a self-regulatory mechanism for immune responses. Fas ligand has also been found to be expressed constitutively at sites of immune privilege such as the testes and the anterior chamber of the eye. Recently, co-transplantation of Fas ligand-transfected myoblasts in association with islet cell allografts was shown to prolong islet allograft survival but only rarely led to indefinite graft survival. Graft rejection was associated with loss of Fas ligand on the myoblasts, suggesting that direct expression of the transgene on the islets might be more effective. METHODS: A replication-defective adenoviral construct containing murine Fas ligand (Ad/MFL) was prepared by homologous recombination. NIH 3T3 cells, rodent splenocytes, and murine islets were infected with Ad/MFL and examined in vitro for functional murine Fas ligand expression. Survival of Ad/MFL-infected islets was subsequently evaluated in vivo in both syngeneic and allogeneic islet transplantation models. RESULTS: Cell lines and islet allografts transfected with Ad/MFL expressed a functional Fas ligand, capable of inducing apoptosis (confirmed by three distinct assays for DNA fragmentation) in Fas+ targets, but not in Fas- controls. Furthermore, Ad/MFL was able to modify allogeneic immune responses in vitro, as addition of this virus, but not a control adenovirus, significantly reduced proliferation in a mixed lymphocyte reaction. Surprisingly, however, transplantation of islet allografts transfected with Ad/MFL resulted in long-term allograft survival in only 1 of 30 recipients. Moreover, adenoviral-mediated Fas ligand gene transfer was complicated by transient, dose-dependent islet dysfunction, perhaps contributing to the lack of long-term engraftment. CONCLUSION: These data suggest that adenoviral-mediated Fas ligand expression may impair normal islet function in vivo, and indicate that alternative strategies for Fas ligand transgene delivery may be required in this setting.

Adenoviridae↗
PubMed1998

Organ transplantation in the twenty-first century.

Major advances in the understanding of the immunologic process responsible for organ or cellular transplant rejection, a dramatic improvement in available immunosuppressive drugs, development of more sophisticated surgical techniques, and important progress in posttransplant intensive care over the last 30 years have led to a remarkable improvement in success following organ transplantation. Whereas excellent short-term survival of most transplanted organs is readily achieved, graft loss because of chronic rejection and the worsening problem of organ donor shortage remain major concerns in the field of transplantation. Recent advances in immunosuppressive drugs, induction of immunologic tolerance, and gene therapy strategies may help to prolong organ allograft survival in the future. Revised criteria for organ donation and xenotransplantation may one day solve the problem of organ supply. Today, as we approach the next millennium, we are optimistic that the elusive goal of immunologic tolerance will be achieved and perhaps applied to animal tissue. Such will certainly be the challenge for the next century.

Forecasting↗
PubMed1997

Immunologic barriers to hepatic adenoviral gene therapy for transplantation.

Adenoviral gene transfer has potential use to attenuate the immunogenicity of hepatic allografts. However, the clinical application of adenoviral gene therapy is currently impeded by the potent host immune response to the virus that limits the duration of its effects. In these studies, we identify the cellular and humoral immune responses to recombinant adenovirus in the liver of mice and define the immunologic barriers to the successful application of this technology to transplantation. The immunobiology of recombinant adenovirus was studied in mouse liver using vectors containing the lacZ and alkaline phosphatase marker genes. The duration of transgene expression was studied in various immunodeficient mice to determine the mechanism of viral clearance. Adoptive transfer of serum to B lymphocyte deficient mice and neutralizing antibody assays were used to define the antiviral humoral response. Hepatic adenoviral transgene expression was prolonged in animals deficient in CD4+ or CD8+ T cells indicating their importance in viral clearance. Unexpectedly, mice lacking B lymphocytes also had delayed elimination of virus suggesting that B cells play a role in the primary immune response. Effective repeat gene transfer was blocked by adenoviral-specific neutralizing antibody. Therefore, a T lymphocyte response results in viral elimination after a primary intravenous inoculation of recombinant adenovirus and a potent humoral response inhibits effective repeat adenoviral gene transfer. The immunogenicity of the vector must be overcome for adenoviral gene therapy to have therapeutic application for hepatic transplantation.

Adenoviridae↗
PubMed1997

Magnetic resonance angiography of the aortic arch.

Duplex ultrasound and magnetic resonance angiographic (MRA) studies are the principal noninvasive methods for evaluation of extracranial occlusive disease in patients at risk for stroke, but each has limited ability to diagnose aortic arch and arch vessel disease. Recent favorable reports of the nonnephrotoxic contrast agent Gadolinium (Gd) being used to enhance MRA images of the abdominal aorta prompted us to examine its utility for the aortic arch vessels. Prospectively, 28 patients with suspected carotid or arch vessel disease were imaged by contrast arteriographic examination and MRA + Gd of the aortic arch within 30 days of each other. One (for contrast arteriograms) or two (for MRA) blinded readers measured stenoses with the contrast arteriograms as the standard. A total of 196 arch vessels containing 58 stenoses and four occlusions (by arteriogram) were examined with each method. Interobserver agreement for interpretation of MRA studies was substantial (kappa = 0.68). MRA detected all anatomic anomalies (e.g., bovine arch). The correlation of MRA with arteriographic scans for arch vessel stenoses > 50% was sensitivity, 73% (readers 1 and 2); specificity, 98% (reader 1), 89% (reader 2); positive predictive value, 73% (reader 1), 89% (reader 2); negative predictive value, 98% (readers 1 and 2); accuracy, 97% (reader 1), 98% (reader 2). MRA + Gd is an accurate new noninvasive imaging method for detection of significant aortic arch disease. In its current state of development, however, it cannot obviate the need for contrast arteriographic examination.

Aorta, Thoracic↗
PubMed1997

Long-lasting adenovirus transgene expression in mice through neonatal intrathymic tolerance induction without the use of immunosuppression.

The major barrier to the clinical application of adenovirus gene therapy for diseases that require stable transgene expression is the immunogenicity of recombinant adenovirus, which ordinarily limits the duration of its effects to a period of about 2 weeks. We postulated that tolerance to adenovirus could be induced and transgene expression could be prolonged if T lymphocytes underwent thymic selection in the presence of adenovirus antigens. Mice were inoculated in the thymus with a recombinant adenovirus containing the lacZ marker gene during the neonatal period at a time before T-cell maturation had occurred. When the virus was administered intravenously to these mice in adulthood, they were found to have an impaired adenovirus-specific cytotoxic T-lymphocyte response which allowed prolonged hepatic lacZ expression, for up to 260 days. The ability to achieve unresponsiveness to a recombinant adenovirus after inoculation of the thymus in neonates extends the paradigm of intrathymic tolerance induction. Furthermore, this model will enable the study of stable adenovirus transgene expression in vivo without the use of immunosuppression and ultimately may have clinical utility.

Adenoviridae↗
PubMed1997

B-cells are required for the initiation of insulitis and sialitis in nonobese diabetic mice.

Nonobese diabetic (NOD) mice spontaneously develop an acute onset of hyperglycemia reminiscent of human type I diabetes. The disease is the end result of a mononuclear cell infiltration of pancreatic islets (insulitis), culminating in the selective destruction of islet beta-cells by autoreactive T-cells. NOD mice also exhibit defects in B-cell tolerance as manifested by the presence of autoantibodies against islet cell autoantigens. Based on the potential ability of B-cells to act as antigen presenting cells, we hypothesized that autoreactive B-cells of NOD mice may be necessary for the activation of islet reactive CD4+ T-cells. In the present study, we utilized an anti-mu antibody to induce in vivo depletion of B-cells and found that B-cell depletion completely abrogates the development of insulitis and sialitis in NOD mice. In contrast, control IgG-treated NOD mice developed insulitis and sialitis by 5 weeks of age. Additionally, the discontinuation of anti-mu chain antibody treatment led to the full restoration of the B-cell pool and the reappearance of insulitis and sialitis. Thus, we conclude that B-cells are a requisite cell population for the genesis of the inflammatory lesions of the islets of Langerhans. This finding suggests that autoreactive B-cells may act as the antigen presenting cells necessary for the initial activation of beta-cell-reactive CD4+ T-cells implicated in the pathogenesis of autoimmune diabetes.

Age Factors↗
PubMed1996

The fate of bypass grafts to angiographically occult runoff vessels detected by magnetic resonance angiography.

PURPOSE: Magnetic resonance angiography (MRA) is a noninvasive vascular imaging technique that is more sensitive than contrast arteriography (CA) for the detection of patent distal runoff vessels. This technique has facilitated performance of MRA-directed bypass procedures for patients who were believed not to be bypass candidates because of the absence of a suitable target vessel on the preoperative CA. The fate of bypasses to these angiographically occult runoff vessels is unknown, however, and it has been proposed that patients with angiographically occult runoff may have aggressive occlusive disease, rendering bypass procedures ultimately futile. METHODS: Between April 1992 and February 1995, 212 autogenous vein infrageniculate bypasses were performed for limb-salvage indications, 22 (12%) to angiographically occult runoff vessels. Results of bypasses performed to angiographically occult vessels were compared with those of bypasses to CA-detected runoff vessels. Life-table analysis of graft-patency and limb-salvage rates was performed. RESULTS: The accuracy of the MRA-predicted patency of angiographically occult vessels was confirmed in every case by the operative findings. Life-table analysis revealed no significant difference in primary graft patency (p > 0.05) or limb-salvage (p > 0.05) rates between patients with bypasses to runoff vessels seen by MRA alone. At 35 months after surgery, the primary graft patency rate was 68% for bypasses to CA-detected vessel bypass and 67% for MRA-detected vessels. The limb salvage rate was 83% for CA-detected vessel bypass patients and 78% for patients with angiographically occult runoff. CONCLUSIONS: MRA can accurately identify patent runoff vessels not visualized by CA. Results of bypasses performed to angiographically occult runoff vessels are similar to those of bypasses performed to vessels detected by CA. MRA should be performed in patients in whom CA fails to reveal runoff vessels suitable for use in a limb-salvage procedure. The greater sensitivity of MRA may facilitate successful bypass surgery and improve the overall limb-salvage rate.

Aged↗
PubMed1996

Prolongation of adenoviral transgene expression in mouse liver by T lymphocyte subset depletion.

Although first generation recombinant adenoviruses are efficient vehicles for gene transfer, their immunogenicity precludes long-term persistence. We show that adenoviral transgene expression in the liver of normal mice is prolonged from a baseline of less than 2 weeks to 7 weeks by depleting CD4+ T lymphocytes with thymectomy and a 3-day course of anti-CD4 monoclonal antibody or by nonselectively depleting T cells with a single dose of anti-thymocyte serum (ATS). Transgene expression persisted despite the development of an antiviral humoral immune response by 3 weeks after virus administration. In vitro assays of T lymphocyte function revealed an initial diminished capacity to proliferate in the presence of adenoviral antigens in animals depleted of CD4+ T cells or given anti-thymocyte serum. Eventual loss of recombinant gene expression coincided with the development of adenovirus-specific cytotoxic T lymphocyte activity in vitro. Immunosuppression provides a useful experimental tool to elucidate the immunobiology of recombinant adenoviruses and may have clinical application to adenovirus-mediated gene therapy.

Adenoviruses, Human↗
PubMed1995

Survival of MHC-deficient mouse heterotopic cardiac allografts.

The immunologic mechanisms involved in the destruction of murine cardiac allografts were evaluated using MHC-deficient mice. Specifically, we examined the survival of immediately vascularized heterotopic adult cardiac grafts deficient in MHC class I, MHC class II, or both MHC class I and II antigens following transplantation to allogeneic hosts. We observed indefinite cardiac graft survival when donors lacked MHC class II or both MHC I and II antigens. In parallel experiments, we studied the survival of cardiac grafts harvested from normal donors in recipients severely depleted of either CD4 (class II-deficient mice) or CD8 (class I-deficient mice) T cells. Graft survival was dramatically prolonged in the absence of CD4 but not CD8 T cells. Collectively, our results demonstrate that the interaction of host CD4 T cells with donor class II antigens is critical to the rejection of murine cardiac grafts.

Animals↗
PubMed1995

Gene transfer to the thymus. A means of abrogating the immune response to recombinant adenovirus.

OBJECTIVE: The authors investigated whether adenoviral gene transfer to the thymus could be accomplished in vivo and whether immunologic unresponsiveness to recombinant adenovirus could be induced by intrathymic inoculation. SUMMARY BACKGROUND DATA: A major barrier to the clinical application of adenovirus-mediated gene therapy for diseases requiring long-lasting gene expression is the immunogenicity of adenoviral vectors, which limits the duration of its effects. In other experimental models, intrathymic inoculation of foreign proteins or cells has proven to be an effective means to induce immunologic tolerance. METHODS: The efficiency of gene transfer to the mouse thymus after direct inoculation of recombinant adenovirus was compared with that of several other vectors. Animals inoculated with adenovirus-infected pancreatic islets into the thymus were tested for unresponsiveness to the virus with a subsequent challenge of adenovirus administered into the liver by intravenous injection. RESULTS: Adenovirus accomplished highly efficient gene transfer to the thymus, unlike plasmid DNA, DNA-liposome complexes, retrovirus, and adeno-associated virus. Adenoviral transgene expression was transient in the thymus of immunocompetent mice but persistent in CD8+ T-cell-deficient and severe combined immunodeficiency (SCID) mice, implicating the role of cytotoxic T lymphocytes in viral clearance. Intrathymic transplantation of syngeneic pancreatic islet cells infected with adenovirus impaired the normal antiviral cytotoxic T-lymphocyte response and prolonged hepatic transgene expression after an intravenous challenge with adenovirus. CONCLUSIONS: Recombinant adenovirus accomplishes highly efficient gene transfer to the thymus in vivo. Intrathymic inoculation of adenovirus-infected islets can be used to induce immunologic unresponsiveness to the adenoviral vector and, potentially, to other proteins that it might be engineered to encode.

Adenoviridae↗