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Biomedical subjects

C Hammer

Publications and source records attributed to C Hammer.

At least 307 records · Page 17Linked to original sources
PubMedDate not supplied

Detection of class II antigens on human nasal cartilage.

The presence and distribution of class II antigens on human nasal cartilage was investigated using monoclonal antibodies directed against HLA-DR, HLA-DP, and HLA-DQ molecules. Tissue sections and chondrocytes in suspension were prepared for immunoperoxidase staining and flow cytometric analysis. Class II antigens were detected primarily on the perichondrium. In contrast, chondrocytes, either isolated or in tissue sections, were completely negative, suggesting that cells of the perichondrium, may, by themselves, be capable of initiating a rejection process.

Antibodies, Monoclonal↗
PubMedDate not supplied

Combining the hDAF transgene with the GP IIb/IIIa inhibitor tirofiban improves heart performance and reduces myocardial damage following hyperacute rejection in an ex vivo perfusion model.

Xenograft rejection is associated with vascular injury resulting at least in part from platelet activation, and rejected xenografts invariably demonstrate intravascular thrombosis. Assuming that complement activation is a major determinant of humoral immune reactions bringing about platelet-endothelial cell interactions, we tested the effects of the specific platelet glycoprotein IIb/IIIa inhibitor tirofiban in combination with the human decay accelerating factor (hDAF) transgene on hyperacute rejection of pig hearts. Four groups were studied in a working heart-perfusion model. Pig hearts transgenic for hDAF and nontransgenic pig hearts were perfused with human blood containing tirofiban or with unmodified human blood. Cardiac output, stroke work index, and creatine phosphokinases were measured for the evaluation of the extent of myocardial damage. Consumption of complement components was determined. Endothelial deposition of fibrin and intravascular thrombosis were evaluated. Tirofiban improved cardiac output and stroke work index of nontransgenic pig hearts and was able to further increase hemodynamic function of hDAF transgenic pig hearts. Low levels of creatine phosphokinases also revealed a cardioprotective effect of tirofiban. However, a further extension of the survival of hDAF transgenic pig hearts could not be achieved, although tirofiban prolonged beating time of nontransgenic pig hearts. Tirofiban was able to reduce the consumption of complement components independently of hDAF. Intravascular evidence of fibrin and thrombosis tended to be particularly reduced by the combination of tirofiban and hDAF. Thus, the application of tirofiban together with hDAF improves the performance of pig hearts by reducing myocardial damage and intravascular thrombosis.

Acute Disease↗
PubMedDate not supplied

Mean xenograft survival of 14.6 days in a small group of hDAF-transgenic pig hearts transplanted orthotopically into baboons.

INTRODUCTION: In a discordant orthotopic xenotransplantation model (pig-to-baboon) donor pigs expressing human decay accelerating factor (hDAF) as a regulator of complement activity were used to prevent hyperacute xenograft rejection (HXR). We investigated a modified immunosuppressive therapy consisting of ERL080 (Novartis Pharma AG, Base, Switzerland), cyclosporin A (Neoral), steroids, and a cyclophosphamide (CyP) induction protocol with several reduced doses to prevent acute vascular rejection (AVR). METHODS: Donor hearts were harvested from hDAF-transgenic pigs (18.8 +/- 2.6 kg, Imutran Ltd., a Novartis Pharma AG Company). Four adult baboons (25.6 +/- 2.7 kg) with high titers of xenoreactive antibodies (XAb) served as recipients. Serological and hemodynamic parameters were measured. Finally, myocardial tissue was sampled for histological and immunohistochemical examinations. RESULTS: In the first baboon, an acute graft failure occurred after 1 hour due to preservation injury. The second succumbed after 11.1 day due to an acute renal failure. The third died after 13.1 days of an ileus. The fourth baboon had continuously excellent cardiac function (mean echocardiographic ejection fraction, 69.2%), but succumbed on day 20 due to anemia. Corrected mean xenograft survival (excluding the first baboon because of a technical failure) was 14.6 +/- 2.6 days. XAb decreased after day 3 to constantly low levels (<1:64 titer) after CyP induction. White blood cell count decreased from 10.3 +/- 0.8 to 0.9 +/- 0.3 G/L after day 3. Macroscopically and histologically no typical signs of HXR or severe AVR could be detected. CONCLUSIONS: These results confirm that hDAF transgen blocks HXR in this life-supporting model. AVR was prevented by using a modified quadruple immunosuppressive drug combination (Neoral, ERL080, steroids, and several small single doses of CyP). An optimum "fine-tuning" of immunosuppression is required to achieve the best risk-benefit ratio.

Animals↗
PubMedDate not supplied

Combination of hDAF-transgenic pig hearts and immunoadsorption in heterotopic xenotransplantation of immunosuppressed baboons.

INTRODUCTION: Hyperacute xenograft rejection (HXR) and acute vascular rejection (AVR) after xenotransplantation are triggered by xenoreactive antibodies (XAb) and an activated complement cascade. In a heterotopic (abdominal) xenotransplantation model we combined immunoadsorption (IA, Ig-Therasorb column) and a quadruple immunosuppressive drug therapy in recipient baboons with donor pig hearts transgenic for human decay accelerating factor (hDAF). METHODS: According to XAb titers between 6 and 14 cycles of IA were performed preoperatively in 4 recipient baboons (18.6 +/- 2.5 kg). Hearts of hDAF-transgenic donor pigs (6.1 +/- 1.1 kg, Imutran Ltd., a Novartis Pharma AG Company, Basel, Switzerland) were heterotopically transplanted using the abdominal technique in baboons. Immunosuppression consisted of cyclophosphamide (CyP) induction therapy, ERL080 (Novartis Pharma AG), cyclosporin A (CyA, Neoral), and steroids. Blood levels of mycophenolate, CyA, immunoglobulins (Ig), anti-pig-antibodies, complement factors, and cardiac enzymes were determined. Abdominal electrocardiography (ECG), echocardiography, and palpation were used for monitoring of the pig hearts. Myocardial tissue specimens were examined using immunohistochemistry, light microscope (LM), and electron microscope (EM). RESULTS: Ten cycles of IA alone removed 78% of XAb and accordingly IgM, IgG, IgA, complement C3, and C4. None of the xenografts was hyperacutely rejected, but xenograft failure occurred after 5.0 +/- 1.3 days (range, 2.4-8.0 days) because of an AVR associated with a rapid XAb increase within 24 hours. White blood cell count (10.3 +/- 2.2 G/L) showed a maximum of 13.1 +/- 2.1 (day 1) and constant levels (1.4 +/- 0.3-2.1 +/- 1.3 G/L) between day 3 and 6. Histology (LM/EM) showed massive hemorrhage, necrosis, and vascular thrombi as signs of AVR. CONCLUSION: Although HXR was prevented by using IA and hDAF-transgenic donor hearts, AVR was not avoided due to insufficient immunosuppressive regimen used and a missed postoperative IA treatment as a result of an inefficient control of XAb production.

Adrenal Cortex Hormones↗
PubMedDate not supplied

Behavior of tissue-engineered human cartilage after transplantation into nude mice.

Cartilage lacks the ability to regenerate structural defects. Therefore, autologous grafting has been used routinely to replace cartilaginous lesions. Because tissue engineering of human cartilage with the help of bioresorbable polymer scaffolds is possible in experimental models, the demand for the clinical application grows. In this study we present an analysis of the behavior of transplants made of human chondrocyte pools, agarose and the resorbable polymer scaffold Ethisorb and a preliminary comparison with transplants made of single patients' cells and Ethisorb but without the additional ingredient agarose. Chondrocytes were isolated from the matrix of human septal cartilage by enzymatic digestion. The pool cells were kept in monolayer culture for 2 weeks, the single patients' cells for 3-4 weeks. Chondrocyte pools were suspended in agarose and seeded into the resorbable polymer scaffold Ethisorb. Single patients' cells were seeded without agarose. All cell-polymer constructs were kept in perfusion culture for 10-14 days and transplanted subcutaneously into thymusaplastic nude mice. Additionally we implanted Ethisorb fleeces embedded in agarose without chondrocytes. After 6, 12 and 24 weeks the animals were sacrificed and the specimens were explanted and analyzed histochemically and immunohistochemically. Polymer scaffolds not seeded with chondrocytes did not show cartilage formation. Resorption was complete after 12 weeks in vivo. Transplants from cell pools remained mechanically stable over 24 weeks apart from four transplants that were resorbed completely. Cartilage formation was observed in all pool-specimens with the presence of chondronic structures and a homogeneous matrix containing hyaline cartilage-specific matrix molecules such as collagen type II. Single patients' transplants showed hyaline cartilage matrix synthesis and mechanical stability as well. Chondrocyte pools are a suitable method to study cartilage engineering of human cells in vitro and in vivo in experimental models. Under clinical conditions it is, however, necessary to study the generation of cartilage from single patients' cells. We showed that it is possible without additional ingredients such as agarose. However, variations in the preliminary results show that the clinical application with human cells is more difficult than one would expect when using human chondrocyte pools. Further studies need to be performed to find out which individual factors influence the in vitro engineered cartilage's fate in vivo.

Journal Article↗
PubMedDate not supplied

The function of antibody and complement in the lysis of bacteria.

The factors controlling lysis of gram-negative bacteria by complement are being investigated systematically. The first question was how smooth Salmonella minnesota, which has on its surface lipopolysaccharide with long O polysaccharide side chains, avoids lysis. Rough organisms are serum sensitive. In both smooth and rough organisms, complement components are deposited on the surface and the lytic sequence proceeds to completion. However, with serum-resistant organisms the membrane attack complex (MAC), composed of late-acting complement proteins, does not successfully insert into the outer membrane to cause membrane damage. At the completion of the lytic sequence, the hydrophobic MAC is shed. C3b, which directs late component assembly, is deposited on the longest O polysaccharide side chains on these smooth organisms, where it does not direct successful insertion of the MAC into the outer membrane. Serum-resistant gonococci sequester the MAC on the organism's surface in association with specific outer membrane components, where it does no damage to the outer membrane. Antibody appears to mediate site-directed complement component deposition in a number of systems. Thus, depending on antibody specificity, complement may be deposited on the organism's surface to cause successful complement attack or may block complement attack induced by bactericidal antibody. Monoclonal antibodies of the same isotype directed at different epitopes on the same bacterial surface antigen may either induce lysis or block lytic attack.

Antibodies, Bacterial↗
PubMedDate not supplied

Human immunodeficiency virus cannot productively infect freshly cultured human cartilage cells.

The use of cartilage allografts is being discussed because of the possible transmission of the human immunodeficiency virus (HIV). To further delineate the possibility for an HIV infection of cartilage cells the susceptibility and permissivity of normal human chondrocytes to HIV-1 was assessed in culture. Isolated cartilage cells were incubated during 30 days with the HIV, testing the production of viral p24 antigens and the formation of particle-bound reverse transcriptase (RT) in the supernatant. The H9 cell line was used as positive control. The production of p24 antigen did not occur on chondrocytes during the whole culture time. Furthermore, no RT activity was detected throughout the entire experimental period. Our results indicate clearly that HIV was not able to infect cartilage cells under these in vitro conditions, and, conclusively, HIV infection of cartilage in vivo is improbable.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Synthesis of human cartilage using organotypic cell culture.

The limited supply of fresh autologous cartilage tissue for use in reconstructive surgery necessitates the use of vital banked allografts. A feasible in vitro production of cartilage tissue composed of living cells requires the use of modern tissue culture techniques retaining the phenotypic characteristics of chondrocytes. With this purpose in mind, human chondrocytes were isolated and cultured using different culture procedures: monolayer, suspension and agar gel. The differentiation state of chondrocytes as well as proteoglycan and collagen syntheses were assessed by histochemical and immunohistochemical methods. Whereas chondrocytes in monolayer displayed an unstable phenotype and tended to dedifferentiate, in three-dimensional culture the chondrocytes remained morphologically, phenotypically and functionally differentiated. Furthermore, an accumulation of matrix products pericellularly was observed in the agar gel. The results suggest that three-dimensional cultures in agar gel may allow the in vitro production of bioartificial cartilage for transplantation.

Agar↗
PubMedDate not supplied

Tracheal transplantation: demonstration of HLA class II subregion gene products on human trachea.

The present morphological study was designed to investigate the expression of HLA class II subregion gene products on human trachea. Frozen sections from the tracheas of 20 cadavers not suffering from ear, nose or throat diseases were studied immunohistochemically using monoclonal antibodies which recognize monomorphic determinants of HLA-DR, -DP and -DQ molecules. Positive reactions could be detected in the airway epithelium and mixed glands. HLA-DR and -DP showed a stronger presence than HLA-DQ. Our results indicate that tracheal mucosa may be the major antigenic structure of the trachea and therefore responsible for the immunogenic action of allogenic tracheal transplants.

HLA-DP Antigens↗
PubMedDate not supplied

Bridging to transplant: allogeneic heart transplantation after xenografting.

Xenografting seems to be a solution to use to bridge time intervals when desperately needed allograft cannot be obtained. A following allograft was never ventured. Nine dogs (weight, 20 to 25 kg; age, 2 years) underwent right cervical heart transplantation. Donors were silver foxes (3 to 4 kg). The animals were treated by triple-drug therapy consisting of cyclosporine, methylprednisolone, and azathioprine in clinical dosages. For control, six recipients received only allogeneic hearts and the identical immunosuppression. After rejection of the xenograft, a second allogeneic heart was anastomosed subsequently to the same right cervical vessels. Routine histologic and immunohistologic examinations were performed. Thromboxane B2 and 6-keto-prostaglandin F1 alpha were determined daily in peripheral blood. After final rejection the sensitization of the recipient was controlled by hemagglutination test. Survival time of the xenografts was 9.6 +/- 1.2 days; the subsequent allogeneic hearts under the same therapy beat for 4.5 +/- 5.0 days. The average survival time of control hearts was 18 +/- 1.9 days. The five hyperacute second allografts showed signs of humoral rejection by absence of inflammation. The release of thromboxane B2 was different in hyperacute, accelerated, or cellular rejection. In contrast to the long-functioning grafts, thromboxane B2 persisted during hyperacute rejection at a high level. However, 6-keto-prostaglandin F1 alpha showed no significant differences between longtime survivors and hyperacute rejecting hearts. After xenogeneic transplantation, all recipients showed hemagglutinating titers between 1:4 and 1:16. Allogeneic grafts have a different kinetics of rejection after xenogeneic heart transplantation compared with control hearts. Thromboxane B2 seems to be an important mediator in hyperacute rejection.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Ketoprostaglandin F1 alpha↗
PubMedDate not supplied

Kinetics and dynamics of acute rejection after heterotopic heart transplantation.

Right cervical, heterotopic heart transplantation was performed in 18 mongrel dogs. Study design was based on three different groups (n = 3 x 6). Standard immunosuppression consisted of triple drug therapy in all dogs. Groups II and III received high dose steroids during acute rejection. In group III the native hearts of previous recipients (groups I and II) were used as donors for heterotopic transplantation ("domino" principle). The hearts were examined by daily transmural biventricular biopsies and graded according to Billingham classification. Cytoimmunologic monitoring (n = 345; activation index from peripheral and coronary sinus blood) and fast Fourier transformation ECG (n = 80; area under the curve; surface recordings) served as daily noninvasive methods. Optionally antimyosin scintigraphy (n = 25; single photon emission computed tomography; heart-to-lung ratio) was performed and immunohistologically confirmed by peroxidase staining of the antibody (n = 61). Kinetics of rejection was not uniform in group I (onset after 5.7 days) and biphasic in group II (clear rejection-free interval: 6.8 days). Group III developed a continuously persisting rejection, despite repeated high-dose steroids, with an early onset (3.2 days). The invasive data, consisting of 587 punch biopsies, showed no significant difference between right and left ventricular rejection. Clearly focal rejection appeared in 51.5% of the cases, with subendocardial involvement in 54%. Cytoimmunologic monitoring significantly (p less than 0.001) correlated with daily biopsies in groups I and II. The activation index from coronary sinus blood was two times higher than in peripheral blood. Fast Fourier transform ECG identified the onset of rejection with great accuracy (p less than 0.01). The heart-to-lung ratio of antimyosin scintigraphy corresponded exactly to the various stages of rejection (p less than 0.001). High-dose steroids led to a clear reduction of the ratio in 26% cases. Peroxidase staining showed typical locations of the antibody, depending on the grade of rejection (p less than 0.001). Considering the results of pathology in this transplantation model, relying on endomyocardial biopsy alone in a clinical setting may not seem advisable. Although the results of this study must be confirmed clinically, the simultaneous use of cytoimmunologic monitoring and fast Fourier transformation ECG may prove to be valuable to day-to-day monitoring for acute rejection in the early postoperative course. If both methods indicate the onset of an acute rejection, antimyosin scintigraphy and endomyocardial biopsy, respectively, should be performed to confirm and grade the suspected diagnosis.

Animals↗
PubMedDate not supplied

[Presence and distribution of HLA-DR, HLA-DP and HLA-DQ transplant antigens in the human tympanum].

The present morphological study was designed to investigate the expression of HLA class II subregion gene products on human tympanic membrane. Frozen sections from tympanic membrane of 10 cadavers were studied immunohistochemically using monoclonal antibodies. Positive reactions could be detected in the epidermal layer and the subepidermal connective tissue layer of the lamina propia. The implications of our findings on the clinical field of tympanic membrane allografting are discussed.

Histocompatibility Antigens Class II↗
PubMedDate not supplied

Xenogeneic and allogeneic canine heart transplantation: a model for cytologic and immunologic monitoring of rejection mechanisms.

In the model of heterotopic intrathoracic heart transplantation, rejections of the graft are not lethal for the recipient animal. Therefore it is possible to follow the immunologic rejection mechanism to the final stage. Allogeneic dog hearts (n = 6) and xenogeneic fox hearts (n = 6) were transplanted. Immunosuppression therapy included cyclosporine and methylprednisolone. Cytoimmunologic monitoring was done every second day. Due to fluctuations of lymphocyte subpopulations and their immature forms, endomyocardial biopsies were performed. The transplanted allogeneic hearts survived for 53.2 +/- 14.8 days if treated with cyclosporine (historical control group without immunosuppression 6.8 +/- 0.8 days). Xenogeneic fox hearts stopped beating after 20.2 +/- 4.1 days (historical control 8.4 +/- 1.9 days). The allogeneic grafts were all rejected in an acute cellular fashion, whereas xenogeneic transplanted hearts showed humoral and cellular rejection mechanisms. Monitoring of circulating inflammatory cells allowed differentiation between humoral and cellular rejection, which was confirmed by histology. Both types of rejection were accompanied by an increase of lymphocytes and their activated forms. Differentiation of lymphocyte subpopulations revealed a significant increase of surface IgG-positive B-lymphocytes under humoral rejection, whereas acute cellular rejection episodes showed a substantial increase of surface IgG-negative lymphocytes. Humoral rejection that developed even with cyclosporine administration was not influenced, whereas cellular rejections were controlled by increasing methylprednisolone to 250 mg/day for 3 days.

Animals↗
PubMedDate not supplied

Cytoimmunological monitoring in acute rejection and viral, bacterial or fungal infection following transplantation.

This study assessed the ability of immunomonitoring to differentiate between acute cardiac rejection and viral, bacterial or fungal infections, using data of thirty-five cyclosporine treated heart and heart-lung transplant recipients. Peripheral blood samples were analyzed daily for 20 days, then three times weekly until the patient's discharge. Later, peripheral blood was examined every fourteen days on an outpatient basis. White blood cells were counted and differentiated. A mononuclear concentrate was obtained by the Ficoll-Hypaque gradient and centrifugation method, and cytocentrifuged onto slides. The cells were stained by a five minute method. Percentages of lymphocytes, prelymphoblasts, lymphoblasts, large granular lymphocytes and monocytes were calculated. When activated cells were detected, aliquots of the mononuclear concentrate were labeled using monoclonal antibodies. In these thirty-five patients, more than 60 acute rejection episodes were diagnosed by the cytoimmunological method. Acute rejection was characterized by a significant rise of the number of leukocytes, lymphocytes, prelymphoblasts and lymphoblasts. The T-lymphocyte population increased while the B-cells remained normal. Ninety-five percent of all acute rejection episodes were diagnosed using cytoimmunological parameters. During viral infection more than 20% of the mononuclear cells were large granular lymphocytes and the OKT4/OKT8 ratio was less than one. During bacterial and fungal infections the B-lymphocytes increased to 40% of the mononuclear cells. In addition, juvenile polymorphs appeared in the mononuclear concentrate and the OKT4/OKT8 ratio was within normal limits (1.5 to 2.5).(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗