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Biomedical subjects

D W Scott

Publications and source records attributed to D W Scott.

At least 37 records · Page 2Linked to original sources
PubMed2000

Activation-induced cell death in B lymphocytes.

Upon encountering the antigen (Ag), the immune system can either develop a specific immune response or enter a specific state of unresponsiveness, tolerance. The response of B cells to their specific Ag can be activation and proliferation, leading to the immune response, or anergy and activation-induced cell death (AICD), leading to tolerance. AICD in B lymphocytes is a highly regulated event initiated by crosslinking of the B cell receptor (BCR). BCR engagement initiates several signaling events such as activation of PLCgamma, Ras, and PI3K, which generally speaking, lead to survival. However, in the absence of survival signals (CD40 or IL-4R engagement), BCR crosslinking can also promote apoptotic signal transduction pathways such as activation of effector caspases, expression of pro-apoptotic genes, and inhibition of pro-survival genes. The complex interplay between survival and death signals determines the B cell fate and, consequently, the immune response.

Animals↗
PubMed2000

Retroviral gene therapy with an immunoglobulin-antigen fusion construct protects from experimental autoimmune uveitis.

Immunoglobulins can serve as tolerogenic carriers for antigens, and B cells can function as tolerogenic antigen-presenting cells. We used this principle to design a strategy for gene therapy of experimental autoimmune uveitis, a cell-mediated autoimmune disease model for human uveitis induced with the uveitogenic interphotoreceptor retinoid-binding protein (IRBP). A retroviral vector was constructed containing a major uveitogenic IRBP epitope in frame with mouse IgG1 heavy chain. This construct was used to transduce peripheral B cells, which were infused into syngeneic recipients. A single infusion of transduced cells, 10 days before uveitogenic challenge, protected mice from clinical disease induced with the epitope or with the native IRBP protein. Protected mice had reduced antigen-specific responses, but showed no evidence for a classic Th1/Th2 response shift or for generalized anergy. Protection was not transferable, arguing against a mechanism dependent on regulatory cells. Importantly, the treatment was protective when initiated 7 days after uveitogenic immunization or concurrently with adoptive transfer of primed uveitogenic T cells. We suggest that this form of gene therapy can induce epitope-specific protection not only in naive, but also in already primed recipients, thus providing a protocol for treatment of established autoimmunity.

Animals↗
PubMed2000

Feline papillomas and papillomaviruses.

Papillomaviruses (PVs) are highly species- and site-specific pathogens of stratified squamous epithelium. Although PV infections in the various Felidae are rarely reported, we identified productive infections in six cat species. PV-induced proliferative skin or mucous membrane lesions were confirmed by immunohistochemical screening for papillomavirus-specific capsid antigens. Seven monoclonal antibodies, each of which reacts with an immunodominant antigenic determinant of the bovine papillomavirus L1 gene product, revealed that feline PV capsid epitopes were conserved to various degrees. This battery of monoclonal antibodies established differential expression patterns among cutaneous and oral PVs of snow leopards and domestic cats, suggesting that they represent distinct viruses. Clinically, the lesions in all species and anatomic sites were locally extensive and frequently multiple. Histologically, the areas of epidermal hyperplasia were flat with a similarity to benign tumors induced by cutaneotropic, carcinogenic PVs in immunosuppressed human patients. Limited restriction endonuclease analyses of viral genomic DNA confirmed the variability among three viral genomes recovered from available frozen tissue. Because most previous PV isolates have been species specific, these studies suggest that at least eight different cat papillomaviruses infect the oral cavity (tentative designations: Asian lion, Panthera leo, P1PV; snow leopard, Panthera uncia, PuPV-1; bobcat, Felis rufus, FrPV; Florida panther, Felis concolor, FcPV; clouded leopard, Neofelis nebulosa, NnPV; and domestic cat, Felis domesticus, FdPV-2) or skin (domestic cat, F. domesticus, FdPV-1; and snow leopard, P. uncia, PuPV-2).

Animals↗
PubMed1999

Induction of hyporesponsiveness to intact foreign protein via retroviral-mediated gene expression: the IgG scaffold is important for induction and maintenance of immune hyporesponsiveness.

IgG molecules can be highly tolerogenic carriers for associated antigens. Previously, we reported that recipients of bone marrow or lipopolysaccharide-stimulated B-cell blasts, both of which were retrovirally gene-transferred with an immunodominant peptide in-frame with the variable region of a murine IgG heavy chain, were rendered profoundly unresponsive to that epitope. To further investigate whether tolerance to larger molecules can be achieved via this approach and whether the IgG scaffold is important for induction and maintenance of immunological tolerance, we engineered two retroviral constructs encoding the cI lambda repressor (MBAE-1-102 and MBAE-1-102-IgG) for gene transfer. Our results show that recipients of bone marrow or peripheral B cells, transduced with the MBAE-1-102-IgG recombinant, are hyporesponsive to p1-102. In addition, the self-IgG scaffold enhanced the induction and maintenance of such an immune hyporesponsiveness. Thus, our studies demonstrate that in vivo-expressed IgG heavy chain fusion protein can be processed and presented on the appropriate MHC class II, resulting in hyporesponsiveness to that antigen and offering an additional therapeutic approach to autoimmune diseases.

Animals↗
PubMed1999

Antihistamines in the management of allergic pruritus in dogs and cats.

Antihistamines clearly have a place in the management of pruritus in the atopic dog and cat and, in this paper, important aspects of pharmacology and pharmacokinetics, adverse effects and precautions, and clinical use of these compounds are reviewed. Successful use of antihistamines is dependent on, among other considerations, the adherence to recommended doses and frequencies of administration, the recognition and control of concurrent and secondary factors, the willingness to try several different compounds, and the realisation that these agents are best employed in a preventive fashion.

Animals↗
PubMed1999

Regulation of p27Kip1 accumulation in murine B-lymphoma cells: role of c-Myc and calcium.

IgM cross-linking induces G1 arrest and apoptosis in murine B-lymphoma cells. It prevents pRb phosphorylation by decreasing cyclin-dependent kinase 2 activity via the up-regulation of cyclin kinase inhibitor p27Kip1. Anti-IgM also causes an increase in cytosolic free calcium and a loss of c-myc mRNA and protein. This down-regulation of c-Myc is prevented by CD40L, which rescues cells from anti-IgM-induced apoptosis. In this study, we addressed the mechanism(s) of anti-IgM-induced p27Kip1 accumulation. We examined effects of early events in B-cell receptor-mediated signaling, c-Myc down-regulation, and an increase in free calcium on p27Kip1. Down-regulation of c-myc alone had no effect on p27Kip1; neither did an increase in free calcium alone. Together, these two events led to p27Kip1 induction, growth arrest, and apoptosis. CD40L, the calcium chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester, and cyclosporin A all prevented anti-IgM-induced p27Kip1 accumulation, suggesting that both the decrease in c-Myc expression and an increase in free calcium are necessary for p27Kip1 up-regulation.

Amino Acid Chloromethyl Ketones↗
PubMed1998

An ongoing immune response to HIV envelope gp120 in human CD4-transgenic mice contributes to T cell decline upon intravenous administration of gp120.

The mechanisms accounting for T cell depletion in AIDS patients are not yet fully understood, nor are the roles of host factors in HIV pathogenesis. We show here that an ongoing humoral immune response to HIV gp120 can sensitize non-infected cells towards apoptosis. Thus, i.v. injection of 1 microg recombinant(r) gp120 into gp120-immunized human CD4-transgenic mice (huCD4 Tg), which express huCD4 on both T and B cells, results in T and B cell depletion in peripheral blood and lymphoid tissues. On day 6 after a bolus injection of gp120, the numbers of peripheral T cells and B cells in gp120-immunized huCD4 Tg decreased sevenfold and two- to threefold, respectively. Annexin V staining revealed a higher percentage of early apoptotic cells on day 1 of gp120 i.v. injection from gp120-primed huCD4 Tg spleens compared to gp120-primed controls. Boosting the primed huCD4 Tg mice with soluble gp120 and hen egg-white lysozyme led to lower secondary titers to both antigens than found in controls. Furthermore, splenocytes from gp120-pretreated immunized huCD4 Tg had a lower level of stimulation in response to anti-CD3 treatment. These in vivo results are consistent with in vitro data demonstrating that cross-linking CD4 on splenocytes of huCD4 Tg by rgp120SF2 and anti-gp120 not only sensitizes T cells for apoptosis, but also induces apoptosis per se, and suggest that anti-gp120 responsiveness can contribute to T cell depletion in AIDS.

Animals↗
PubMed1998

Efficacy of clindamycin hydrochloride capsules for the treatment of deep pyoderma due to Staphylococcus intermedius infection in dogs.

Clindamycin hydrochloride capsules (11 mg/kg body weight, q24 h) were administered orally to 20 dogs with deep staphylococcal pyoderma. Response to therapy was excellent in 100% of the dogs. Duration of therapy varied from 21 to 91 d, with an average duration of 45 d. Relapses occurred in 25% of the dogs within a 3-month period. One dog vomited when the clindamycin was given on an empty stomach. Under the conditions of the study, clindamycin was an effective, safe, and convenient antibiotic for the treatment of deep staphylococcal pyoderma in dogs.

Administration, Oral↗
PubMed1997

Both resting and activated B lymphocytes expressing engineered peptide-Ig molecules serve as highly efficient tolerogenic vehicles in immunocompetent adult recipients.

To test the potential for genetically transferring foreign sequences into autologous cells for specific modulation of immunity, we have generated transgenic mice that express an engineered peptide-IgG construct in the peripheral B cell compartment. B cells from these mice express and can be stimulated to secrete a murine IgG1 chain grafted with residues 12-26 from bacteriophage A cI repressor protein in-frame at the heavy chain N terminus. As expected, 12-26-IgG transgenic mice are profoundly tolerant to the peptide at both the T and B cell levels. Importantly, the injection of transgenic whole spleen, purified B cells, or even bone marrow cells into normal, immunocompetent adults results in profound peptide-specific T cell tolerance, as well as partial B cell tolerance. Injection of LPS-activated peptide-Ig-expressing B cells was uniquely effective at diminishing an ongoing humoral immune response typical of both Th1 and Th2 help. Since fixed transgenic B cells were tolerogenic, this suggests that secretion of the fusion protein is not required for tolerogenicity. These results show that an engineered self Ig, as well as B lymphocytes expressing epitopes from such a fusion protein, can regulate both cellular and humoral immune responses. Moreover, these studies provide the basis for expressing foreign epitopes on engineered IgG for the induction of gene-transferred tolerogenesis in autoimmune states.

Age Factors↗
PubMed1997

Role of c-myc and p27 in anti-IgM induced B-lymphoma apoptosis.

Crosslinking membrane IgM receptors on a set of murine B cell lymphomas leads to a rapid increase in c-myc, followed by a decrease in its expression to undetectable levels by 8-24 hours. These cells die soon thereafter via apoptosis. IgD receptor crosslinking also leads to an increase in c-myc expression, but it remains above baseline levels for more than 24 hours; these cells continue to proliferate and do not die. We previously reported that antisense oligonucleotides for c-myc prevented growth arrest and cell death in these lymphomas, independent of the presence of mitogenic CpG motifs. Indeed, antisense for c-myc actually led to a stabilization of c-myc message and protein. Growth arrest in these cells is dependent on the increased synthesis of the p27 cyclin kinase inhibitor (Kip1) normally induced after anti-IgM crosslinking. Consistent with its biologic effects, anti-IgD does not cause an increase in p27. Since dexamethasone causes a loss of myc and synergizes with the anti-IgM signal, we suggest that accelerated cell death with this steroid in the presence of anti-IgM is due to a more rapid degradation of this oncogene product. Finally, we propose that c-myc drives the transcription or activation of an inhibitor of the p27 Kip (Kipi). Hence, loss of c-myc in response to anti-IgM signals in these B-cell lymphomas leads to upregulation of p27, growth arrest and apoptosis. It follows that maintenance of c-myc in these B-cell lymphomas should lead to survival and no increase in p27.

Animals↗
PubMed1997

Focal necrotizing panniculitis and vascular necrosis in rats given subcutaneous injections of cocaine hydrochloride.

Subcutaneous injections of cocaine hydrochloride in sterile physiological saline were administered to rats at a dosage of 20 or 40 mg.kg-1. Resultant skin lesions included focal areas of alopecia (within 1 to 2 days) which progressed to necrosis (within 2 to 7 days). Histologically, the skin lesions were characterized by necrotizing panniculitis and vascular necrosis, with only small numbers of inflammatory cells. The lesions may be ischemic in nature, and associated with cytotoxic properties of cocaine.

Animals↗
PubMed1997

Genetically transferred central and peripheral immune tolerance via retroviral-mediated expression of immunogenic epitopes in hematopoietic progenitors or peripheral B lymphocytes.

BACKGROUND: Based on the hypothesis that IgGs are potent tolerogens and that immature lymphohematopoietic antigen-presenting cells (APC), and even mature peripheral B cells, may be effective APC for tolerance induction, we designed an immunoglobulin fusion protein retroviral expression vector to test the role of B cells in a novel gene therapy strategy for the transfer of immune tolerance. METHODS: An immunodominant epitope (residues 12-26 of the lambda repressor cI protein) was fused in frame to an IgG heavy chain in a retroviral vector, which was used to infect either bone marrow cells or activated peripheral B lymphocytes. These cells were transferred into syngeneic recipients, who were subsequently challenged with the 12-26 peptide in adjuvant. RESULTS: Bone marrow (BM) chimeras generated with retrovirally transduced bone marrow were shown to be profoundly unresponsive to the 12-26 peptide at both the humoral and cellular levels, but were competent to respond to an unrelated protein (lysozyme or PPD). Importantly, we also show that immunocompetent adult recipients infused with transduced mature, activated B lymphocytes, are rendered unresponsive by this treatment. Surprisingly, lymphoid-deficient BM progenitors from syngeneic SCID donors could also be transduced to produce tolerogenic APC. CONCLUSIONS: Our data suggest that activated B cells are sufficient to be effective tolerogenic APC in immunocompetent adult mice, but that nonlymphoid cells may also induce tolerance in reconstituted hosts. This approach for gene-transferred tolerogenesis has the potential to be maintained indefinitely, and it requires only knowledge of cDNA sequences of target antigens.

Amino Acid Sequence↗
PubMed1997

Effect of an omega-3/omega-6 fatty acid-containing commercial lamb and rice diet on pruritus in atopic dogs: results of a single-blinded study.

A commercial, lamb and rice, dog food with an omega-6:omega-3 fatty acid ratio of 5.5:1 was fed in a single-blinded, self-controlled clinical trial to 18 atopic dogs. The pruritus in 8 of these dogs (44.4%) was satisfactorily controlled within 7 to 21 d, returned within 3 to 14 d after the diet was withdrawn, and was again controlled when the diet was reinstated. Plasma and skin levels of examined fatty acids changed in all 18 dogs when their diet was switched to the test diet. Dogs responding to the test diet had a different pattern of fatty acid change as compared to the dogs which failed to respond to the diet, suggesting that there are subsets of atopic dogs with different fatty acid metabolism capabilities.

Animals↗
PubMed1996

Differential susceptibility to anti-receptor induced apoptosis in adult murine B-cells: role of B1 cells.

We and others have recently found that mature murine B cells can be induced to undergo apoptosis, in vitro, in a dose-dependent manner, by extensive crosslinking of membrane IgM with polyclonal anti-mu. During the analysis of tolerance in transgenic mice expressing rearranged IgM or IgM + IgD receptors, we observed that, Sp6 anti-TNP Ig and anti-MHC transgenic splenocytes, would undergo receptor-mediated apoptosis in vitro just like their normal, non-transgenic littermates. However, transgenic mice expressing rearranged receptors typical of B1 cells, not only contained large numbers of CD5+ cells in their spleens, but these cells failed to undergo apoptosis under conditions that led to programmed cell death in normal splenocytes. B1 spleen cells also failed to proliferate with anti-IgM, although the responsiveness of cells from the other transgenic lines varied depending on the background strains. These differences are due in part, to strain differences, but they also imply that the response pattern of transgenic B cells reflects not only the subset composition in this organ, but also the transgenic specificity of the receptor.

Animals↗
PubMed1996

Epitope-specific tolerance induction with an engineered immunoglobulin.

Isologous and heterologous immunoglobulins have been shown to be extremely effective as tolerogenic carriers for nearly 30 years. The efficacy of these proteins is due in part to their long half-life in vivo, as well as their ability to crosslink surface IgM with Fc receptors. The concept of using IgG as a carrier molecule to induce unresponsiveness in the adult immune system has been exploited for simple haptens, such as nucleosides, as well as for peptides. To further evaluate the in vivo potential of these molecules for inducing tolerance to a defined epitope, we have engineered a fusion protein of mouse IgG1 with the immunodominant epitope 12-26 from bacteriophage lambda cI repressor protein. This 15-mer, which contains both a B-cell and T-cell epitope, has been fused in-frame to the N terminus of a mouse heavy chain IgG1 construct, thus creating a "genetic hapten-carrier" system. We describe a novel in vitro and in vivo experimental system for studying the feasibility of engineered tolerogens, consisting of a recombinant flagellin challenge antigen and a murine IgG1 tolerogen, both expressing the lambda repressor epitope 12-26. Herein, we show that peptide-grafted IgG molecules injected i.v., or expressed by transfected, autologous B cells, can efficiently modulate the cellular and humoral immune responses to immunodominant epitopes. This model displays the feasibility of "tailor-designing" immune responses to whole antigens by selecting epitopes for either tolerance or immunity.

Amino Acid Sequence↗