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K M Murphy

Publications and source records attributed to K M Murphy.

At least 73 records · Page 4Linked to original sources
PubMed1998

Low dose TGF-beta attenuates IL-12 responsiveness in murine Th cells.

Expression of IL-12Rs is one important checkpoint for Th1 development. BALB/c DO11.10 CD4+ T cells stimulated by Ag in neutral conditions lose expression of the IL-12R beta 2 subunit and become unresponsive to IL-12. In contrast, B10.D2 or F1 (BALB/c x B10.D2) DO11.10 CD4+ T cells maintain IL-12R beta 2 expression when stimulated similarly. Here we show that the loss of IL-12 responsiveness by BALB/c T cells involves the action of endogenous TGF-beta. BALB/c T cells stimulated in the presence of anti-TGF-beta specifically maintain IL-12 responsiveness, express IL-12R beta 2 mRNA, and can stimulate nitric oxide production in peritoneal exudate cells. Low concentrations of TGF-beta added exogenously during primary activation of B10.D2 or F1 T cells significantly inhibit their development of IL-12 responsiveness. These effects of anti-TGF-beta are dependent on endogenous IFN-gamma and are inhibited by exogenously added IL-4. Thus, at least one effect of TGF-beta on Th1/Th2 development may be the attenuation of IL-12R beta 2 expression.

Adjuvants, Immunologic↗
PubMed1998

Patchy distribution of NMDAR1 subunit immunoreactivity in developing visual cortex.

Development of ocular dominance columns is dependent on patterned retinal activity, and yet patterned activity alone cannot explain all aspects of cortical column development. Features intrinsic to the cortex have been proposed to interact with activity to guide the patterning of cortical columns (), and the NMDA receptor, because of its role in experience-dependent plasticity, is an obvious candidate. Using immunohistochemical techniques, we found a transiently patchy distribution of the NMDA receptor 1 (NMDAR1) subunit in kitten visual cortex. Regularly spaced patches of NMDAR1-immunoreactive neurons were found at the top of the cortical plate in the developing visual cortex at 2 weeks of age. At 4-5 weeks of age, the radial extent of the NMDAR1 patches spanned the supragranular layers, and by 12 weeks of age, this nonuniform pattern of NMDAR1 immunostaining was no longer apparent. Monocular visual experience prevented the expression of the NMDAR1 patches, but just 4 d of subsequent binocular visual experience was sufficient to promote expression of the patches. Furthermore, the NMDAR1 patches tended to be associated with the borders of ocular dominance columns. These results suggest that the degree of plasticity associated with NMDA-mediated mechanisms is elevated in local regions across the tangential extent of the visual cortex and that the NMDAR1 patches may participate in sculpting the overall arrangement of visual cortical columns.

Animals↗
PubMed1998

IL-1 alpha and TNF-alpha are required for IL-12-induced development of Th1 cells producing high levels of IFN-gamma in BALB/c but not C57BL/6 mice.

The development of Th1- or Th2-type responses determines the type of immune response that is elicited in response to Ag. Responsiveness to IL-12 is critical for the development of Th1-type CD4+ T cells required for cell-mediated immune responses. Addition of IL-12 to primary cultures of CD4+ T cells stimulated with OVA and splenocytes or dendritic cells resulted in the development of a Th1 phenotype with the capacity to secrete high levels of IFN-gamma upon restimulation with splenic APC. The present study shows that using dendritic cells to present Ag upon restimulation reveals a requirement for additional cofactors, including IL-1 alpha and TNF-alpha, which were provided by spleen cells but not dendritic cells. Furthermore, these cofactors are required for optimal IL-12-induced Th1 development in BALB/c but not C57BL/6 mice. This differential requirement for such cofactors in IL-12-driven Th1 development may play a role in genetic predisposition to Th1 or Th2 responses to infectious agents.

Adjuvants, Immunologic↗
PubMed1998

T lymphocyte differentiation in the periphery.

The development of immune responses is significantly influenced by emerging patterns of cytokine expression in activated CD4+ T cells. Recent efforts have clarified both cellular and molecular mechanisms, and within the past year include significant observations on potential sources of IL-4 leading to Th2 development against certain pathogens, and insights into early responses and genetic susceptibility to experimental murine Leishmaniasis and transcriptional regulation of the IL-4 locus. Advances in Th1 development have included greater understanding of IL-12 receptors in Th1 development, data regarding IFN-gamma gene expression and clarification of the action of the new cytokine IL-18.

Animals↗
PubMed1998

Inhibition of Th1 development mediated by GATA-3 through an IL-4-independent mechanism.

Recently, the transcription factor GATA-3 was shown to be selectively expressed in Th2 but not Th1 cells and to augment Th2-specific cytokines. Here, we show that loss of GATA-3 expression by developing Th1 cells requires IL-12 signaling through Stat4 and does not simply result from an absence of IL-4. Moreover, we demonstrate a novel role for GATA-3 in directly repressing Th1 development distinct from its positive actions on Th2-specific cytokines. GATA-3 inhibits Th1 cytokines by a cell-intrinsic mechanism that is not dependent on IL-4 and that may involve repression of IL-12 signaling. Thus, GATA-3 expression and IL-12 signaling are mutually antagonistic, which facilitates rapid dominance of one pathway during early Th development, producing a stable divergence in cytokine profiles.

Animals↗
PubMed1998

Compliance with timolol treatment in glaucoma.

PURPOSE: To assess levels of compliance in elderly patients on timolol eyedrops for glaucoma. METHODS: A postal questionnaire was sent from the general practitioner to 86 patients over 55 years of age on repeat prescriptions for timolol eyedrops. The questionnaire asked details about the duration of treatment, family history, the level of understanding of the disease and the importance of treatment, other regular medication, side-effects attributed to the drops and how often patients omitted their drops. A search of practice and local hospital dispensing data was carried out to assess how frequently monthly repeat prescriptions for timolol eyedrops were dispensed over a 12 month period. This allowed a total volume to be calculated for each patient. RESULTS: Twenty-four per cent of patients admitted to omitting eyedrops either occasionally or frequently. Fifty-one per cent were found to have had insufficient drops dispensed to comply with treatment as prescribed. In non-complaint patients the mean period without drops was 85 days of the year, with a maximum of 165 days. CONCLUSION: Compliance with treatment is poor and patients underestimate their level of defaulting when questioned.

Aged↗
PubMed1997

T cell genetic background determines maintenance of IL-12 signaling: effects on BALB/c and B10.D2 T helper cell type 1 phenotype development.

In this report, we examined the molecular basis underlying the genetic difference between BALB/c and B10.D2 T cells for T helper phenotype development in vitro. We found a strain-dependent difference in early maintenance of IL-12 responsiveness by T cells developing in vitro in unmanipulated (neutral) conditions. Thus, when activated without addition of exogenous cytokines or neutralization of endogenous cytokines, B10.D2, but not BALB/c, T cells remain responsive to IL-12 when activated for 7 days. The pattern of IL-12 responsiveness correlated with expression of the IL-12R signaling subunit, IL-12R beta2, and with IL-12-induced STAT4 phosphorylation. When activated under neutral conditions, BALB/c T cells rapidly lose IL-12R beta2 expression, STAT4 phosphorylation, and functional IL-12 responsiveness. More efficient maintenance of IL-12R beta2 expression by B10.D2 T cells activated under neutral conditions may explain the previously observed increase in IFN-gamma production relative to that of BALB/c. This difference could potentially provide greater protection from certain pathogens that do not immediately elicit strong Th1-inducing conditions via activation of the innate immune system.

Animals↗
PubMed1997

Regulation of the interleukin (IL)-12R beta 2 subunit expression in developing T helper 1 (Th1) and Th2 cells.

The developmental commitment to a T helper 1 (Th1)- or Th2-type response can significantly influence host immunity to pathogens. Extinction of the IL-12 signaling pathway during early Th2 development provides a mechanism that allows stable phenotype commitment. In this report we demonstrate that extinction of IL-12 signaling in early Th2 cells results from a selective loss of IL-12 receptor (IL-12R) beta 2 subunit expression. To determine the basis for this selective loss, we examined IL-12R beta 2 subunit expression during Th cell development in response to T cell treatment with different cytokines. IL-12R beta 2 is not expressed by naive resting CD4+ T cells, but is induced upon antigen activation through the T cell receptor. Importantly, IL-4 and IFN-gamma were found to significantly modify IL-12 receptor beta 2 expression after T cell activation. IL-4 inhibited IL-12R beta 2 expression leading to the loss of IL-12 signaling, providing an important point of regulation to promote commitment to the Th2 pathway. IFN-gamma treatment of early developing Th2 cells maintained IL-12R beta 2 expression and restored the ability of these cells to functionally respond to IL-12, but did not directly inhibit IL-4 or induce IFN-gamma production. Thus, IFN-gamma may prevent early Th cells from premature commitment to the Th2 pathway. Controlling the expression of the IL-12R beta 2 subunit could be an important therapeutic target for the redirection of ongoing Th cell responses.

Animals↗
PubMed1997

Identification of IL-4 promoter elements conferring Th2-restricted expression during T helper cell subset development.

Selective cytokine gene expression by T cell subsets underlies polarization of cellular and humoral immune responses. Our interest has been to define the molecular basis for restricted cytokine expression by Th1 and Th2 cells. IL-4 is selectively expressed by Th2 cells, providing a model for Th2-specific gene expression. To allow for promoter analysis during the process of Th1/Th2 differentiation within a normal cellular context, we have taken a transgenic approach. We generated a series of murine transgenic lines harboring both the DO11.10 alphabeta-TCR transgene and the luciferase gene driven by regions of the IL-4 promoter. The results identify proximal promoter regions that provide significantly Th2-restricted IL-4 gene expression. The IL-4 -741- to +60-bp region allows, on the average, 40-fold higher inducible reporter activity in Th2 cells than in Th1 cells. When trimerized, the region spanning -88 to -61 bp, containing a composite NF-AT/AP-1 site, also confers significant Th2-specific reporter activity. These results suggest that trans-acting factors binding this NF-AT/AP-1 composite site cooperate to allow substantial Th2-selective reporter expression. Finally, because reporter expression is low relative to endogenous IL-4 mRNA in activated Th2 cells, we suggest that additional control elements outside of the IL-4 promoter may be required to enhance overall IL-4 gene activity.

Adaptor Protein Complex alpha Subunits↗
PubMed1997

Genetic control of interleukin 12 responsiveness: implications for disease pathogenesis.

We examined the effect of genetic background on Th1/Th2 development. We discuss data demonstrating that genetic background is an important determinant of interleukin-12 (IL-12) responsiveness and the potential implications for disease progression in murine experimental leishmaniasis. Genetic analysis of the differential control of IL-12 responsiveness led to the identification of a controlling locus on the middle portion of murine chromosome 11. This genetic region (or its human counterpart, 5q31) has been associated with increased disease susceptibilities for several atopic, infectious, and autoimmune disorders. We discuss potential roles for genetic control of IL-12 responsiveness in the development of these diseases.

Animals↗
PubMed1996

Functional diversity of helper T lymphocytes.

The existence of subsets of CD4+ helper T lymphocytes that differ in their cytokine secretion patterns and effector functions provides a framework for understanding the heterogeneity of normal and pathological immune responses. Defining the cellular and molecular mechanisms of helper-T-cell differentiation should lead to rational strategies for manipulating immune responses for prophylaxis and therapy.

Animals↗
PubMed1996

Genetic mapping of a murine locus controlling development of T helper 1/T helper 2 type responses.

Genetic background of the T cell can influence T helper (Th) phenotype development, with some murine strains (e.g., B10.D2) favoring Th1 development and others (e.g., BALB/c) favoring Th2 development. Recently we found that B10.D2 exhibit an intrinsically greater capacity to maintain interleukin 12 (IL-12) responsiveness under neutral conditions in vitro compared with BALB/c T cells, allowing for prolonged capacity to undergo IL-12-induced Th1 development. To begin identification of the loci controlling this genetic effect, we used a T-cell antigen receptor-transgenic system for in vitro analysis of intercrosses between BALB/c and B10.D2 mice and have identified a locus on murine chromosome 11 that controls the maintenance of IL-12 responsiveness, and therefore the subsequent Th1/Th2 response. This chromosomal region is syntenic with a locus on human chromosome 5q31.1 shown to be associated with elevated serum IgE levels, suggesting that genetic control of Th1/Th2 differentiation in mouse, and of atopy development in humans, may be expressed through similar mechanisms.

Animals↗
PubMed1996

Non-uniform distribution of the NMDAR1 receptor subunit in kitten visual cortex at the peak of the critical period.

PURPOSE: The development of columnar systems in the visual cortex, in particular ocular dominance columns, is dependent on experiential activity in conjunction with NMDA-mediated plasticity mechanisms. Recent experiments, however, have shown that certain aspects of the columnar organization of the visual cortex, such as the spacing of columns, are not changed by manipulations that affect the pattern of retinal activity. This raises the possibility that features intrinsic to the visual cortex may play a crucial role in the development of cortical columns and that a non-uniform distribution of NMDA receptors in the developing visual cortex could form the link between activity and intrinsic cortical modularity. METHODS: To examine this possibility we used immunohistochemical techniques to label the NMDAR1 receptor subunit protein in kitten visual cortex. The arrangement of the NMDAR1 subunit was visualized (using a monoclonal antibody) in flattened and coronal sections through visual cortex. The tangential and laminar distributions of NMDAR1 immunoreactivity (NMDAR1ir) were studied at the peak of the critical period for plasticity (4-5 weeks of age) in the developing kitten visual cortex. RESULTS: At the ages examined there was a non-uniform distribution of NMDAR1 immunoreactivity in the visual cortex. These patches of darker NMDAR1 label were found in layers 2/3 and extended up into layer 1. Thus, during development neurons expressing the NMDAR1 receptor subunit were distributed in a patchy fashion in the upper layers of the kitten visual cortex. CONCLUSIONS: This suggests that NMDA-mediated activity-dependent plasticity may not occur uniformly across the tangential extent of the visual cortex, and raises the possibility that the arrangement of NMDAR1 patches may guide the emergence of nascent columns in the developing visual cortex.

Animals↗
PubMed1996

Genetic susceptibility to Leishmania: IL-12 responsiveness in TH1 cell development.

The genetic background of T lymphocytes influences development of the T helper (TH) phenotype, resulting in either resistance or susceptibility of certain mouse strains to pathogens such as Leishmania major. With an in vitro model system, a difference in maintenance of responsiveness of T cells to interleukin-12 (IL-12) was detected between BALB/c and B10.D2 mice. Although naive T cells from both strains initially responded to IL-12, BALB/c T cells lost IL-12 responsiveness after stimulation with antigen in vitro, even when cocultured with B10.D2 T cells. Thus, susceptibility of BALB/c mice to infection with L. major may derive from the loss of the ability to generate IL-12-induced TH1 responses rather than from an IL-4-induced TH2 response.

Animals↗
PubMed1996

Roles of IFN-gamma and IFN-alpha in IL-12-induced T helper cell-1 development.

IL-12 and IL-4 direct T cell development toward Th1 and Th2 phenotypes, respectively. While IFN-gamma and IFN-alpha have been reported to regulate Th1 development as well, the mechanism and cellular locus of their effects are unclear. In this study, we use a TCR-transgenic system to examine the actions of these cytokines on CD4+ T cell phenotype development. We find that neither IFN-gamma nor IFN-alpha can induce Th1 development alone. However, IFN-gamma can significantly augment IL-12 priming for subsequent IFN-gamma production by T cells. Interestingly, lymphocyte endothelial cell adhesion molecule-1bright (naive) T cells require IFN-gamma during primary activation for maximal IL-12-induced Th1 development, whereas lymphocyte endothelial cell adhesion molecule-1dull (memory) T cells do not. IFN-alpha only partially substitutes for IFN-gamma in promoting IL-12-induced Th1 development. When the endogenous IFN-gamma present in primary T cell cultures is neutralized, IFN-alpha treatment augments IL-12-induced effects on inhibition of subsequent IL-4 production, but fails to significantly enhance IL-12 priming for subsequent IFN-gamma production. Thus, our data suggest that IFN-gamma provides a direct costimulatory signal to T cells to up-regulate IL-12-induced Th1 development and may operate by inducing IL-12 responsiveness in naive T cells.

Animals↗