Biomedical subjects

R M Locksley

Publications and source records attributed to R M Locksley.

At least 19 recordsLinked to original sources

PubMed1999

Altered ligands reveal limited plasticity in the T cell response to a pathogenic epitope.

Experimental leishmaniasis offers a well characterized model of T helper type 1 cell (Th1)-mediated control of infection by an intracellular organism. Susceptible BALB/c mice aberrantly develop Th2 cells in response to infection and are unable to control parasite dissemination. The early CD4(+) T cell response in these mice is oligoclonal and reflects the expansion of Vbeta4/ Valpha8-bearing T cells in response to a single epitope from the parasite Leishmania homologue of mammalian RACK1 (LACK) antigen. Interleukin 4 (IL-4) generated by these cells is believed to direct the subsequent Th2 response. We used T cells from T cell receptor-transgenic mice expressing such a Vbeta4/Valpha8 receptor to characterize altered peptide ligands with similar affinity for I-Ad. Such altered ligands failed to activate IL-4 production from transgenic LACK-specific T cells or following injection into BALB/c mice. Pretreatment of susceptible mice with altered peptide ligands substantially altered the course of subsequent infection. The ability to confer a healer phenotype on otherwise susceptible mice using altered peptides that differed by a single amino acid suggests limited diversity in the endogenous T cell repertoire recognizing this antigen.

Amino Acid Sequence↗

PubMed1999

Susceptibility to infectious diseases: Leishmania as a paradigm.

The diverse response of individuals within populations to infectious pathogens remains poorly understood, although genetic determinants undoubtedly contribute in substantial ways to the outcome of infection. In a mouse model of infection with the intramacrophage protozoan Leishmania major, susceptibility correlates both with aberrant helper T cell differentiation biased towards the production of interleukin 4 and with the presence of an endogenous CD4 T cell repertoire that recognizes an immunodominant parasite antigen with high frequency. In the setting of the particular ecological niche occupied by Leishmania, this combination of otherwise unrelated factors synergizes to result in exquisite susceptibility to this single pathogen, without seemingly compromising host defenses against other agents. Similar paradigms could underlie susceptibility to other pathogenic organisms.

Amino Acid Sequence↗

PubMed1998

Genetic regulation of commitment to interleukin 4 production by a CD4(+) T cell-intrinsic mechanism.

The dysregulated expression of interleukin 4 (IL-4) can have deleterious effects on the outcome of infectious and allergic diseases. Despite this, the mechanisms by which naive T cells commit to IL-4 expression during differentiation into mature effector cells remain incompletely defined. As compared to cells from most strains of mice, activated CD4(+) T cells from BALB mice show a bias towards IL-4 production and T helper 2 commitment in vitro and in vivo. Here, we show that this bias arises not from an increase in the amount of IL-4 produced per cell, but rather from an increase in the proportion of CD4(+) T cells that commit to IL-4 expression. This strain-specific difference in commitment was independent of signals mediated via the IL-4 receptor and hence occurred upstream of potential autoregulatory effects of IL-4. Segregation analysis of the phenotype in an experimental backcross cohort implicated a polymorphic locus on chromosome 16. Consistent with a role in differentiation, expression of the phenotype was CD4(+) T cell intrinsic and was evident as early as 16 h after the activation of naive T cells. Probabilistic gene activation is proposed as a T cell-intrinsic mechanism capable of modulating the proportion of naive T cells that commit to IL-4 production.

Animals↗

PubMed1998

Requirement for IL-13 independently of IL-4 in experimental asthma.

The pathogenesis of asthma reflects, in part, the activity of T cell cytokines. Murine models support participation of interleukin-4 (IL-4) and the IL-4 receptor in asthma. Selective neutralization of IL-13, a cytokine related to IL-4 that also binds to the alpha chain of the IL-4 receptor, ameliorated the asthma phenotype, including airway hyperresponsiveness, eosinophil recruitment, and mucus overproduction. Administration of either IL-13 or IL-4 conferred an asthma-like phenotype to nonimmunized T cell-deficient mice by an IL-4 receptor alpha chain-dependent pathway. This pathway may underlie the genetic associations of asthma with both the human 5q31 locus and the IL-4 receptor.

Adoptive Transfer↗

PubMed1998

Interferon gamma derived from CD4(+) T cells is sufficient to mediate T helper cell type 1 development.

Interferon gamma (IFN-gamma) has been implicated in T helper type 1 (Th1) cell development through its ability to optimize interleukin 12 (IL-12) production from macrophages and IL-12 receptor expression on activated T cells. Various systems have suggested a role for IFN-gamma derived from the innate immune system, particularly natural killer (NK) cells, in mediating Th1 differentiation in vivo. We tested this requirement by reconstituting T cell and IFN-gamma doubly deficient mice with wild-type CD4(+) T cells and challenging the mice with pathogens that elicited either minimal or robust IL-12 in vivo (Leishmania major or Listeria monocytogenes, respectively). Th1 cells developed under both conditions, and this was unaffected by the presence or absence of IFN-gamma in non-T cells. Reconstitution with IFN-gamma-deficient CD4(+) T cells could not reestablish control over L. major, even in the presence of IFN-gamma from the NK compartment. These data demonstrate that activated T cells can maintain responsiveness to IL-12 through elaboration of endogenous IFN-gamma without requirement for an exogenous source of this cytokine.

Animals↗

PubMed1998

Independent and epigenetic regulation of the interleukin-4 alleles in CD4+ T cells.

How an individual effector T cell acquires a particular cytokine expression pattern from many possible patterns remains unclear. CD4+ T cells from F1 mice, which allowed assignment of the parental origin of interleukin-4 (IL-4) transcripts, were divided into clones that expressed IL-4 biallelically or monoallelically from either allele. The allelic pattern was transmitted as a stable epigenetic trait. Regulation of cytokine expression by a mechanism that treats each allele independently suggests a probabilistic process by which a diverse repertoire of combinatorially assorted cytokine gene expression patterns could be generated among the clonally related daughters of a single precursor cell.

Alleles↗

PubMed1998

Control of Leishmania major by a monoclonal alpha beta T cell repertoire.

Little is known regarding the diversity of the host T cell response that is required to maintain immunologic control of microbial pathogens. Leishmania major persist as obligate intracellular parasites within macrophages of the mammalian host. Immunity is dependent upon activation of MHC class II-restricted T cells to an effector state capable of restricting growth and dissemination of the organisms. We generated alpha-beta Leishmania-specific (ABLE) TCR transgenic mice with MHC class II-restricted T cells that recognized an immunodominant Leishmania Ag designated LACK. Naive T cells from ABLE mice proliferated in vitro after incubation with recombinant LACK or with Leishmania-parasitized macrophages and in vivo after injection into infected mice. Infected ABLE mice controlled Leishmania infection almost as well as wild-type mice despite a drastic reduction in the T cell repertoire. ABLE mice were crossed to mice with disruption of the TCR constant region alpha gene to create animals with a single alpha beta T cell repertoire. Although mice deficient in all alpha beta T cells (TCR-C alpha 0 mice) failed to control L. major, mice with a monoclonal alpha beta T cell repertoire (ABLE TCR-C alpha 0 mice) displayed substantial control. The immune system is capable of remarkable efficiency even when constrained to recognition of a single epitope from a complex organism.

Amino Acid Sequence↗

PubMed1998

Development of CD4+ effector T cells and susceptibility to infectious diseases.

The mechanisms by which naive helper T cells differentiate into potent cytokine-expressing effectors remain critical to understanding both successful and aberrant immune responses. Studies using Leishmania major infection of mice have revealed genetic contributions to factors that influence this differentiative process. Further, antigen recognition at the level of the T cell repertoire can also profoundly affect the outcome of disease and the appearance of discrete T cell subsets. It is likely that such mechanisms also underpin genetic susceptibility to diverse other infectious and autoimmune diseases.

Animals↗

PubMed1998

Fellowship training in infectious diseases: a report from the regional and national meetings of infectious diseases division chiefs and program directors.

During the 2-year period April 1995 to April 1997, six regional meetings and one national meeting of division chiefs and program directors of adult infectious diseases programs in the United States were held to review fellowship training. Herein, we report data on job availability and job selection for recently graduated fellows. We summarize discussions on decreasing the number of fellows in training, and we outline suggested components of a core clinical curriculum and of three training tracks--clinician track, clinical investigator track, and basic investigator track.

Adult↗

PubMed1998

Distribution of protein kinase C isoforms after infection of macrophages with Leishmania major.

We characterized the effects of Leishmania infection on activation-induced translocation of protein kinase C (PKC) isoforms in murine bone marrow-derived macrophages. Although PKC-dependent gene expression was attenuated by infection, the distribution and translocation of PKC isoforms were unaffected. However, subsequent dissociation from membranes was substantially delayed for some isoforms, particularly PKCbeta.

Animals↗

PubMed1998

Requirements for allergen-induced airway hyperreactivity in T and B cell-deficient mice.

BACKGROUND: The pathogenesis of asthma is believed to reflect antigen-induced airway inflammation leading to the recruitment of eosinophils and activation of mast cells through cell-associated IgE. Controversies persist however, regarding the relative importance of different pathogenic cells and effector molecules. MATERIALS AND METHODS: A variety of gene-targeted mice were examined for the induction of cholinergic airway hyperresponsiveness (AH), allergic airway inflammation, mucus production, and serum IgE reactivity following intratracheal challenge with a potent allergen. AH was determined using whole-body plethysmography following acetylcholine challenge. Where possible, results were confirmed using neutralizing antibodies and cell-specific reconstitution of immune deficient mice. RESULTS: T and B cell-deficient, recombinase-activating-gene-deficient mice (RAG -/-) failed to develop significant allergic inflammation and AH following allergen challenge. Reconstitution of RAG -/- mice with CD4+ T cells alone was sufficient to restore allergen-induced AH, allergic inflammation, and goblet cell hyperplasia, but not IgE reactivity. Sensitized B cell-deficient mice also developed airway hyperreactivity and lung inflammation comparable to that of wild-type animals, confirming that antibodies were dispensable. Treatment with neutralizing anti-IL-4 antibody or sensitization of IL-4-deficient mice resulted in loss of airway hyperreactivity, whereas treatment with anti-IL-5 antibody or sensitization of IL-5-deficient mice had no effect. CONCLUSIONS: In mice, CD4+ T cells are alone sufficient to mediate many of the pathognomonic changes that occur in human asthma by a mechanism dependent upon IL-4, but independent of IL-5, IgE, or both. Clarification of the role played by CD4+ T cells is likely to stimulate important therapeutic advances in treatment of asthma.

Adoptive Transfer↗

PubMed1998

Disease susceptibility and development of the cytokine repertoire in the murine Leishmania major model.

The murine Leishmania major model has proven fertile ground for the elucidation of CD4+ T cell effector subset differentiation in vivo. The availability of a highly susceptible inbred strain, BALB/c, that develops progressive disease due to the aberrant differentiation of Th2, as opposed to protective Th1, responses, has allowed the identification of both T cell intrinsic as well as T cell extrinsic properties that combine to mediate disease outcome. The intrinsic T cell phenotype relates to the capacity of BALB/c-derived CD4+ T cells to acquire the potential to secrete IL-4 more readily than cells from other strains of mice. The extrinsic T cell phenotype relates to the creation of a T cell repertoire capable of recognizing the immunodominant parasite antigen. Together, the two traits confer the aberrant response seen in susceptible mice challenged with L. major.

Animals↗

PubMed1997

Altered immune responses in interleukin 10 transgenic mice.

Interleukin (IL)-10 is a pleiotropic cytokine which inhibits a broad array of immune parameters including T helper cell type 1 (Th1) cytokine production, antigen presentation, and antigen-specific T cell proliferation. To understand the consequences of altered expression of IL-10 in immune models of autoimmune disease, the response to infectious agents, and the response to tumors, we developed transgenic mice expressing IL-10 under the control of the IL-2 promoter. Upon in vitro stimulation, spleen cells from unimmunized transgenic mice secrete higher levels of IL-10 and lower amounts of IFN-gamma than do controls, although no gross abnormalities were detected in lymphocyte populations or serum Ig levels. Transfer of normally pathogenic CD4(+) CD45RBhigh splenic T cells from IL-10 transgenic mice did not cause colitis in recipient severe combined immunodeficiency mice. Furthermore, co-transfer of these transgenic cells with CD4(+) CD45RBhigh T cells from control mice prevented disease. Transgenic mice retained their resistance to Leishmania major infection, indicating that their cell-mediated immune responses were not globally suppressed. Lastly, in comparison to controls, IL-10 transgenic mice were unable to limit the growth of immunogenic tumors. Administration of blocking IL-10 mAbs restored in vivo antitumor responses in the transgenic mice. These results demonstrate that a single alteration in the T cell cytokine profile can lead to dramatic changes in immune responses in a manner that is stimulus dependent. These mice will be useful in defining differences in inflammatory conditions and cellular immunity mediated by IL-10.

Animals↗

PubMed1997

The N-terminal propiece of interleukin 1 alpha is a transforming nuclear oncoprotein.

Interleukin 1 alpha (IL-1 alpha) is a pleiotropic cytokine involved in the immune response, inflammatory processes, and hematopoiesis, and acts as a mitogen for several malignant cell types, including acute leukemia and Kaposi sarcoma cells. These diverse activities have been exclusively attributed to the plasma membrane receptor-binding, 17-kDa C-terminal component (mature IL-1 alpha) that results from proteolytic processing of the 31- to 33-kDa precursor protein. No biologic function has been ascribed to the unusually large, 16-kDa N-terminal propiece formed as a result of proteolytic processing of IL-1 alpha. We report that the IL-1 alpha N-terminal propiece is concentrated by means of a nuclear localization sequence within the nuclei of both transfected and leukemic cell lines. Overexpression of this component in glomerular mesangial cells, a model perivascular myofibroblast cell type capable of IL-1 alpha synthesis and processing, results in malignant transformation to a spindle cell-type tumor. The functionally bipartite nature of the IL-1 alpha precursor represents a unique combination of the C-terminal, classical cytokine and an N-terminal nuclear oncoprotein. These findings suggest that nuclear transport of the IL-1 alpha N-terminal component may represent a critical component in the transformation of IL-1 alpha-producing cells in the bone marrow or the perivascular area to a malignant phenotype.

Amino Acid Sequence↗

PubMed1997

T helper subset differentiation in the absence of invariant chain.

The outcome of murine infection with Leishmania major is regulated by major histocompatibility complex class II-restricted T helper cells. Invariant chain-deficient (Ii -/-) mice have impaired ability to present major histocompatibility complex class II-restricted antigens, and reduced numbers of CD4+ T cells. Despite these deficits, C57BL/6 Ii -/- mice controlled L. major infection comparably to wild-type mice. As assessed by mRNA analysis and in vitro antigen restimulation for IFN-gamma, Ii -/- mice had normal induction of Th1 subset differentiation even though antigen-dependent proliferation of their lymph node cells was substantially compromised. In addition, BALB/c Ii -/- mice exhibited a progressive course of infection and Th2 effector cell development that were comparable to that seen in wild-type BALB/c mice. We wished to determine whether this unexpected efficiency of T helper subset induction despite inefficient T cell stimulation could be modeled in vitro. In the presence of rIL-12 or rIL-4 naive parasite-specific transgenic T cells could mature into IFN-gamma-or IL-4-secreting T helper cells, respectively, even when antigen presentation was suboptimal or antigen dose was submitogenic. These experiments demonstrate that activation of T helper cells to a threshold required for IL-2 production or proliferation is not required to achieve induction of disease-regulating T helper cell effector functions, and that pathogen-associated secondary activation signals may facilitate the full differentiation of T helper subsets during limiting presentation of antigenic peptides.

Animals↗

PubMed1997

IL-4 rapidly produced by V beta 4 V alpha 8 CD4+ T cells instructs Th2 development and susceptibility to Leishmania major in BALB/c mice.

BALB/c mice develop aberrant T helper 2 (Th2) responses and suffer progressive disease after infection with Leishmania major. These outcomes depend on the production of interleukin-4 (IL-4) early after infection. Here we demonstrate that the burst of IL-4 mRNA, peaking in draining lymph nodes of BALB/c mice 16 hr after infection, occurs within CD4+ T cells that express V beta 4 V alpha 8 T cell receptors. In contrast to control and V beta 6-deficient BALB/c mice, V beta 4-deficient BALB/c mice were resistant to infection, demonstrating the role of these cells in Th2 development. The early IL-4 response was absent in these mice, and T helper 1 responses occurred following infection. Recombinant LACK antigen from L. major induced comparable IL-4 production in V beta 4 V alpha 8 CD4+ cells. Thus, the IL-4 required for Th2 development and susceptibility to L. major is produced by a restricted population of V beta 4 V alpha 8 CD4+ T cells after cognate interaction with a single antigen from this complex organism.

Animals↗

PubMed1997

Impaired Th2 subset development in the absence of CD4.

Prior studies in CD4-deficient mice established the capacity of T helper (Th) lineage cells to mature into Th1 cells. Unexpectedly, challenge of these mice with Nippostrongylus brasiliensis, a Th2-inducing stimulus, failed to result in the development of Th2 cells. Additional studies were performed using CD4+ or CD4-CD8- (double-negative) T cell receptor (TCR) transgenic T cells reactive to LACK antigen of Leishmania major. Double-negative T cells were unable to develop into Th2 cells in vivo, and, unlike CD4+ T cells, could not be primed for interleukin-4 production in vitro. Similarly, CD4+ TCR transgenic T cells primed on antigen-presenting cells expressing mutant MHC class II molecules unable to bind CD4 did not differentiate into Th2 cells. These data suggest that interactions between the TCR, MHC II-peptide complex and CD4 may be involved in Th2 development.

Animals↗

PubMed1997

Immunological tolerance to a pancreatic antigen as a result of local expression of TNFalpha by islet beta cells.

Recent experiments have suggested that tumor necrosis factor alpha (TNFalpha) can down-regulate islet-specific T cells and prevent the development of autoimmune diabetes. Here we demonstrate that transgenic mice expressing both TNFalpha and the Leishmania major LACK antigen in the pancreas (RIP-TNFalpha/RIP-LACK) exhibit an impaired ability to mount a CD4+ T cell response against LACK. In addition, peripheral CD4+ T cells from TCR transgenic mice (TCR-LACK/RIP-TNFalpha/RIP-LACK) produced reduced interleukin-2 but elevated levels of T helper 2 cytokines in response to LACK peptide in vitro. Taken together, our data suggest that TNFalpha may act in vivo to modulate a potentially damaging self-reactive T cell response by inducing tolerance to pancreatic antigens.

Animals↗