Search PubMed⌕ Search

Biomedical subjects

A D Hess

Publications and source records attributed to A D Hess.

At least 109 records · Page 6Linked to original sources
PubMed1987

Cyclosporine and the thymus: influence of irradiation and age on thymic immunopathology and recovery.

With the proper experimental conditions, previous studies have demonstrated that syngeneic and autologous radiation chimeras treated with cyclosporine (CsA) routinely develop a syndrome resembling graft-vs-host disease (GVHD) after CsA is discontinued. The thymus is clearly important in the pathogenesis. Thymectomy prior to CsA prevents the development of syngeneic GVHD and the process can be adoptively transferred via thymocytes. The thymus, however, must be within the field of irradiation and the animal must be young. Here we examine how irradiation and advanced age influence the thymic immunopathologic changes induced by CsA and influence the recovery post-CsA. Young LEW rats, with or without pre-CsA mediastinal irradiation, demonstrate a marked involution of the thymic medulla with associated loss of medullary epithelium, Hassall's corpuscles, class II antigen expression, and maturation of thymocytes. While the control group underwent rapid and complete regeneration of the medulla post-CsA, however, the medullary changes in the irradiated group were prolonged or permanent. Most of these animals had changes of chronic GVHD. Older LEW rats had a more prominent medulla prior to CsA. In contrast to younger rats, the medulla did not show significant involution with CsA. While the Hassall's corpuscles disappeared, the medullae still had fusiform epithelium, dendritic cells, and class II antigen expression. Phenotype stains demonstrated many mature-appearing CD4+/CD8- lymphocytes. In light of evidence indicating the importance of the medullary microenvironment to the maintenance of self tolerance, the medullary effects of CsA are most likely essential to the development of autoimmunity. Young rats rapidly lose the ability to maintain tolerance. While unirradiated rats rapidly reestablish the proper microenvironment following CsA, irradiated rats have a prolonged loss. Older rats may resist the development of autoimmunity by retaining the medullary microenvironment.

Age Factors↗
PubMed1987

Cyclosporine inhibits soluble antigen and alloantigen presentation by human monocytes in vitro.

We examined whether cyclosporine (CsA) interferes with human monocyte processing and presentation of soluble and particulate antigens. Human monocytes were pulsed in the presence of CsA with one of three antigens: tetanus toxoid (TT), diphtheria toxoid (DIP) or cytomegalovirus (CMVx). When these monocytes were co-cultured with immunocompetent T-lymphocytes they were found to be impaired in the induction of proliferative and cytotoxic T-cell responses. At CsA concentrations higher that 0.5 micrograms/ml, proliferation induced by the particulate CMVx antigen was markedly more sensitive than that induced by the soluble TT antigen. In the allogeneic mixed lymphocyte reaction (MLR), pretreatment of responder haplotype monocytes alone with CsA led to reduced reactivity as determined in both proliferative (P less than 0.01) and cell-mediated lympholysis (P less than 0.001) assays. These effects of CsA were not due to direct CsA action of residual CsA carried over with treated monocytes, and were not apparently due to inhibition of interleukin-1 (IL-1) production since exogenous IL-1 could not restore normal responses.

Antigen-Presenting Cells↗
PubMed1987

Calcium and calmodulin antagonists inhibit human malaria parasites (Plasmodium falciparum): implications for drug design.

The malaria parasite has an obligate calcium requirement for normal intracellular growth and invasion of host erythrocytes. Calmodulin (CaM) is a vital calcium-dependent protein present in eukaryotes. We found by radioimmunoassay that free parasites contain CaM. Schizont-infected erythrocytes had CaM levels of 23.3 +/- 2.7 ng per 10(6) cells compared to normals (11.2 +/- 1.5 ng per 10(6) cells). CaM levels were proportional to parasite maturity. Immunoelectron microscopy identified CaM diffusely within the cytoplasm of mature parasites and at the apical end of merozoites within the ductule of rhoptries, which may explain the calcium requirement for invasion. Cyclosporin A (CsA) was also found by electron microscopic autoradiography to concentrate in the food vacuole, as do chloroquine and mefloquine, and to distribute within the cytoplasm of mature parasites. The binding of dansylated CsA to schizont-infected erythrocytes was higher than to normal erythrocytes as analyzed by flow cytometry. Kinetic analysis revealed that binding was saturable for normal and infected erythrocytes and possibly free parasites. Competition for binding existed between dansylated CsA and native CsA as well as the CaM inhibitor W-7 and the classic antimalarial chloroquine. The in vitro growth of Plasmodium falciparum was sensitive to CaM antagonists, and in large part inhibition of the parasite was proportional to known anti-CaM potency. Antagonism existed between combinations of these drugs in multi-drug-resistant strains of P. falciparum, suggesting possible competition for the same binding site. In addition, the malaria parasite was also susceptible to calcium antagonists.

Animals↗
PubMed1987

Cyclosporin A and the thymus. Immunopathology.

Cyclosporin A (CsA) is known to diminish the size of the thymus, especially the thymic medulla. The significance of these changes is not presently understood. This study reveals several immunopathologic changes induced in the thymic medulla by CsA (15 mg/kg/day). The weight and relative size of the thymus dramatically and rapidly involutes, with marked changes observed in 1 week. The medullary thymocytes show segregation of rat T-cell phenotypes as seen in control rats, but the number of such cells is markedly reduced in accordance with the medullary remnant. This is consistent with a maturational arrest of thymocytes. The medullary epithelium was assessed directly by irradiating the control or CsA-treated rats 2 days prior to sacrifice. The epithelium of Hassall's corpuscles was essentially absent in CsA-treated rats but prominent in control rats. The cortical epithelial cells were preserved. Stains for Ia antigen with the anti-OX4 antibody show little change in expression by cortical epithelium, but a marked reduction in the Ia+ medullary cells in the thymocyte purged rats. All of these changes were reversible in the normal rat after cessation of CsA, with near normal recovery in 3 weeks. No morphologic or immunopathologic changes were noted in the cortical thymocytes. These cells did, however, acquire CsA receptors, as detected by the binding of fluorescent dansylated CsA.

Animals↗
PubMed1986

Cyclosporine A, an in vitro calmodulin antagonist, induces nuclear lobulations in human T cell lymphocytes and monocytes.

Cyclosporine A is a noncytotoxic, natural, 11 amino acid cyclic peptide used clinically as an immunosuppressant to prevent organ rejection after transplantation. Cyclosporine A is an in vitro calmodulin antagonist. At the low concentrations required to inhibit calmodulin-dependent phosphodiesterase in vitro, cyclosporine A causes a dramatic alteration in the nuclear morphology of 23% of human peripheral blood mononuclear leukocytes in vitro without loss of viability. The shape of the nucleus changes from ovoid to a distinctive, radially splayed lobulated structure. The changes occur in a dose-dependent manner in 60 min at 37 degrees C. Specific monoclonal antibodies to human leukocytes identify the cells susceptible to nuclear lobulation by cyclosporine A as OKT4 antigen-positive T cell lymphocytes and monocytes. The lobulated nuclei are 2N as determined by flow cytometric measurement of ethidium bromide fluorescence of DNA. The cyclosporine A-induced lobulation of T cell nuclei requires both physiologic temperature and metabolic energy. Although structurally different than cyclosporine A, the calmodulin antagonists R24571 and W-7 [N-(6-aminohexyl)-5-chloro-1-naphthalene-sulfonamide] also produce T cell nuclear lobulations that are indistinguishable from the nuclear lobulations caused by cyclosporine A. These data indicate that nonmitotic structural elements that govern normal nuclear morphology in a subset of mononuclear leukocytes appear to require a calmodulin-mediated process. Cyclosporine A may be a useful noncytotoxic inhibitor of calmodulin-dependent systems that influence nuclear structure and function.

Antigens, Surface↗
PubMed1986

Treatment and prevention of acute graft-versus-host disease with thalidomide in a rat model.

We have investigated the immunosuppressive effects of thalidomide (Thal) in a bone marrow transplant (BMT) model for graft-versus-host disease (GVHD). Lewis rats received RT1-incompatible marrow transplants from ACI rats after total-body irradiation. Twenty-two of twenty-three rats with established severe acute GVHD were successfully treated with Thal. Thal was given for therapy by gavage at 50 mg/kg/day or 100 mg/kg/day for 40 days after GVHD was clinically and histologically present. Fourteen of twenty-two received prophylaxis successfully with Thal at a dose of 50 mg/kg/day or 100 mg/kg/day. Acute GVHD did not develop after the drug was stopped. Three animals treated for severe GVHD later developed chronic GVHD. Chimerism was shown by permanent acceptance of ACI skin grafts and rejection of third-party skin grafts. Lymphocytes from Thal-treated animals likewise did not respond to Lewis or ACI cells in mixed lymphocyte culture but responded to third-party BN lymphocytes. Thal appears to be a potent new agent for therapy and prophylaxis of GVHD.

Animals↗
PubMed1986

Cyclosporine and the immune response: basic aspects.

Cyclosporine (CsA) is a novel immunosuppressive agent currently used clinically, to prevent rejection of solid organ allografts and to prevent graft-vs.-host disease. Early studies in a variety of animal models exhibited transplantation tolerance after limited treatment with this unique agent. The apparent specific immunological unresponsiveness induced by CsA is thought to be maintained by antigen-specific suppressor T lymphocytes. Studies attempting to dissect the mechanism of action of this unique agent suggested that CsA selectively affected different T lymphocyte populations. Cyclosporine was very effective at inhibiting the production of interleukin-2 (IL-2), a soluble lymphokine known to amplify cytotoxic T cell responses and was also capable of preventing IL-2 receptor expression on the precursor cytotoxic T lymphocyte. In contrast, to the effect on T helper cells and on the precursor cytotoxic T lymphocyte, studies in vitro and in vivo demonstrated that CsA had a sparing effect on suppressor T cell induction. More recent studies have indicated that CsA allows for the amplification of suppressor T lymphocytes independent of interleukin-2 indicating that other cellular and/or soluble factors are important for potentiation of suppressor T lymphocyte activity. However, the molecular action of CsA at the cellular level still remains unresolved. Thus, CsA is not only a useful drug in clinical transplantation but it has become increasingly important as an immunologic probe allowing the dissection of complex cellular interactions involved in the immune response.

Animals↗
PubMed1986

Immunological heterogeneity of human monocyte subsets prepared by counterflow centrifugation elutriation.

Human peripheral blood mononuclear cells were separated into three fractions by means of counterflow centrifugation elutriation (CCE). The first fraction, eluted at a flow rate of 24 ml/min, was composed of lymphocytes with less than 2% contaminating esterase-positive cells. The cells in this fraction were incapable of responding to either soluble antigen (tetanus toxoid) or particulate antigen (cytomegalovirus-infected fibroblasts) unless recombined with accessory cells. The second fraction, eluted at a flow rate of 28 ml/min, was composed predominantly (72%) of small Ia, leu M3, and esterase-positive monocytes, which stained weakly with leu 10 antibody. Cells in this fraction efficiently presented soluble and particulate antigens to monocyte-depleted lymphocytes. Of the remaining cells, 87% were large esterase-positive monocytes that labelled strongly with Ia, leu M3, and leu 10. These cells were less efficient in antigen presentation than the small monocytes. However, lymphocytes activated with antigen-pulsed large monocytes exhibited more suppressor cell activity than those activated with antigen-pulsed small monocytes.

Antigen-Presenting Cells↗