Cross-tolerance: a pathway for inducing tolerance to peripheral tissue antigens.
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Animals↗
Biomedical subjects
J F Miller
Publications and source records attributed to J F Miller.
Compartmentalization of bacterial antigens: differential effects on priming of CD8 T cells and protective immunity.
Bacterial pathogens synthesize numerous proteins that are either secreted or localized within bacterial cells. To address the impact of antigen compartmentalization on T cell immunity, we constructed recombinant Listeria monocytogenes that express a model CD8T cell epitope as a secreted or nonsecreted fusion protein. Both forms of the antigen, either secreted into the host cell cytoplasm or retained within bacterial cells, efficiently prime CD8 T cell responses. However, epitope-specific CD8 T cells confer protection only against bacteria secreting the antigen but not against the bacteria expressing the nonsecreted form of the same antigen. This dichotomy as a result of antigen compartmentalization suggests that bacterial antigens are presented by multiple MHC class I pathways to prime CD8 T cells, but only the endogenous pathway provides target antigens for CD8 T cell-mediated protective immunity.
Antigens, Bacterial↗
The threshold for autoimmune T cell killing is influenced by B7-1.
The concept that naive CD4+ and CD8+ T cells require co-stimulatory signals for activation and proliferation is well documented. Less clear is the need for co-stimulation during the effector phase of the T cell response. Here we examined the influence of B7-1 (CD80) during the effector phase of an autoimmune response to pancreatic islets using transgenic mouse lines which expressed B7-1 in either all or only some of their beta cells ("confluent" or "patchy" RIP-B7-1 mice). Transgenic expression of B7-1 in normal mouse islets that co-expressed the pro-inflammatory cytokine, IL-2, resulted in early spontaneous autoimmunity. Islets with IL-2 and "confluent" B7-1 expression were destroyed whereas islets with IL-2 and "patchy" B7-1 expression showed selective killing of the B7-1+ beta cells. Islet-reactive T cells, circulating in the RIP-B7-1/IL-2 mice, rejected syngeneic islet grafts, but only if these expressed B7-1. Introduction of the B7-1 transgene into the nonobese diabetic (NOD) genetic background likewise resulted in early spontaneous autoimmunity, but splenocytes from the diabetic animals could only transfer diabetes to NOD scid recipients that expressed B7-1 on their beta cells. In both these transgenic models, therefore, islet destruction required continuous B7-1 expression by target beta cells. Thus, although the normal repertoire contains T cells with potential islet reactivity, these T cells remain harmless because parenchymal cells like the beta cell cannot normally express B7-1. Our results also have implications for tumor immunotherapy in that the ability of T cells to kill poorly immunogenic targets may be dependent upon B7-1 expression by the target cell itself.
Animals↗
Cross-presentation of self antigens to CD8+ T cells: the balance between tolerance and autoimmunity.
Upon encounter with foreign antigen, tissue-associated antigen-presenting cells (APCs) migrate to draining lymph nodes to prime specific T cells. Using the transgenic RIP-mOVA model, we recently demonstrated that self antigens derived from peripheral tissues are constitutively transported to draining lymph nodes, and can be presented in association with MHC class I molecules by a bone marrow-derived APC population. This form of class I-restricted presentation of exogenous antigen has been referred to as cross-presentation and can induce activation and proliferation of antigen-specific CD8+ T cells. In the absence of CD4+ T cell help, activation of CD8+ T cells is inefficient, and cross-presentation leads to peripheral deletion of autoreactive CD8+ T cells, acting as a mechanism to maintain self-tolerance. If CD4+ T cell help is available, CD8+ T cell responses to self antigens can be rendered immunogenic, leading to autoreactive responses. Whether autoimmunity results from such responses also depends on the tissue location of the antigen. In RIP-mOVA mice, which express the model antigen mOVA (a membrane-bound form of ovalbumin) in the pancreatic beta cells and kidney proximal tubules, OVA-specific CD8+ T cells, activated by cross-presentation, infiltrated the pancreas and caused B cell destruction. Interestingly, however, these cells did not infiltrate the kidney, suggesting that proximal tubular cells are to some extent protected from immune destruction. Analysis of the role of antigen concentration indicates that high doses were required for efficient cross-presentation, suggesting that this pathway is directed towards immune responses to high-dose antigens, such as may be present during viral infection.
Animals↗
Cross-presentation: a general mechanism for CTL immunity and tolerance.
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Animals↗
In vivo and ex vivo regulation of bacterial virulence gene expression.
Bacteria are remarkably adaptable organisms that are able to survive and multiply in diverse and sometimes hostile environments. Adaptability is determined by the complement of genetic information available to an organism and by the mechanisms that control gene expression. In general, gene products conferring a growth or survival advantage in a particular situation are expressed, while unnecessary or deleterious functions are not. Expression of virulence gene products that allow pathogenic bacteria to multiply on and within host cells and tissues are no exception to this rule. Being of little or no use to the bacterium except during specific stages of the infectious cycle, these accessory factors are nearly always subject to tight and coordinate regulation. As a result of recent advances, we are beginning to appreciate the complexities of the interactions between bacteria and their hosts. The ability to probe virulence gene regulation in vivo has broadened our perspectives on pathogenesis.
Animals↗
The structure of mother-child play: young children with Down syndrome and typically developing children.
This study explored developmental changes and effects of Down syndrome on mothers' structuring of their children's play. Mothers and their young children with Down syndrome (n = 28) were compared with socioeconomically matched samples of mothers and their mental age-matched (n = 28) and chronological age-matched (n = 28) typically developing children. Mothers of typically developing children exhibited more object demonstrations with their developmentally younger children, who exhibited less object play. Mothers of children with Down syndrome were more directive and supportive than were mothers of younger and older typically developing children, who did not differ in their frequencies of these behaviors. More maternal supportive object behavior was associated with more object play and vocalization by children with Down syndrome. Mothers and children in all 3 groups were contingently responsive to their partners' behavioral signals.
Child Development↗
The BvgAS virulence control system regulates type III secretion in Bordetella bronchiseptica.
The BvgAS signal transduction system in Bordetella spp. mediates a transition between infectious (Bvg+) and non-infectious (Bvg-) phases by sensing environmental conditions and regulating gene expression. Using differential display, arbitrary-primed polymerase chain reaction (PCR), we identified a gene expressed in the Bvg+ phase of Bordetella bronchiseptica that shows a high degree of sequence similarity to a locus involved in providing energy for type III secretion in pathogenic gram-negative bacteria (yscN in Yersinia spp.). We determined that the expression of this homologue in B. bronchiseptica (designated bscN) is regulated by bvg. Several open reading frames surrounding the bscN locus also show sequence similarity to loci encoding type III secretion apparatus components in other bacteria. An in-frame deletion of bscN in B. bronchiseptica leads to decreased secretion of several proteins, decreased cytotoxicity towards cultured cell lines and a defect in causing tyrosine dephosphorylation of specific proteins in infected cells in vitro. The deletion strain also revealed that bscN-mediated secretion is required for persistent colonization of the trachea in a rat infection model. Loci encoding type III secretion homologues were identified in four strains of B. pertussis and two strains of B. parapertussis. B. pertussis strain 18323 and an ovine isolate of B. parapertussis show significant transcription of the genes in vitro.
Adenosine Triphosphatases↗
Induction of peripheral CD8+ T-cell tolerance by cross-presentation of self antigens.
There is now convincing evidence that CD8+ T cells can be activated by professional antigen-presenting cells which present antigens derived from non-lymphoid tissues in association with MHC class I molecules in the draining lymph nodes. This mechanism, referred to as cross-presentation, enables the immune system to respond to those microorganisms that infect only non-lymphoid tissues. Consistent with this view, cross-presentation was found to focus on antigens expressed in high concentrations and those released from dying cells, which can be expected to result from viral infections. Recent evidence, however, demonstrates that high dose self antigens can be cross-presented constitutively, resulting in the activation of autoreactive CD8+ T cells. This does not lead to auto immunity under physiologic conditions, but to CD95-mediated deletion of the T cells. Cross-presentation can thus engage a well-defined pathway of antigen-induced T-cell death and purge the immune system of autoreactive CD8+ T cells. Low dose self antigens are not cross-presented and are consequently ignored. The immune system therefore uses two strategies to avoid CD8+ T-cell-mediated autoimmunity in the periphery: deletion of autoreactive CD8+ T cells responding to high dose self antigens and ignorance of self antigens expressed at low concentrations.
Animals↗
Filamentous hemagglutinin of Bordetella bronchiseptica is required for efficient establishment of tracheal colonization.
Adherence to ciliated respiratory epithelial cells is considered a critical early step in Bordetella pathogenesis. For Bordetella pertussis, the etiologic agent of whooping cough, several factors have been shown to mediate adherence to cells and cell lines in vitro. These putative adhesins include filamentous hemagglutinin (FHA), fimbriae, pertactin, and pertussis toxin. Determining the precise roles of each of these factors in vivo, however, has been difficult, due in part to the lack of natural-host animal models for use with B. pertussis. Using the closely related species Bordetella bronchiseptica, and by constructing both deletion mutation and ectopic expression mutants, we have shown that FHA is both necessary and sufficient for mediating adherence to a rat lung epithelial (L2) cell line. Using a rat model of respiratory infection, we have shown that FHA is absolutely required, but not sufficient, for tracheal colonization in healthy, unanesthetized animals. FHA was not required for initial tracheal colonization in anesthetized animals, however, suggesting that its role in establishment may be dedicated to overcoming the clearance action of the mucociliary escalator.
Adhesins, Bacterial↗
Neither the Bvg- phase nor the vrg6 locus of Bordetella pertussis is required for respiratory infection in mice.
In Bordetella species, the BvgAS sensory transduction system mediates an alteration between the Bvg+ phase, characterized by expression of adhesins and toxins, and the Bvg- phase, characterized by the expression of motility and coregulated phenotypes in Bordetella bronchiseptica and by the expression of vrg loci in Bordetella pertussis. Since there is no known environmental or animal reservoir for B. pertussis, the causative agent of whooping cough, it has been assumed that this phenotypic alteration must occur within the human host during infection. Consistent with this hypothesis was the observation that a B. pertussis mutant, SK6, containing a TnphoA insertion mutation in a Bvg-repressed gene (vrg6) was defective for tracheal and lung colonization in a mouse model of respiratory infection (D. T. Beattie, R. Shahin, and J. Mekalanos, Infect. Immun. 60:571-577, 1992). This result was inconsistent, however, with the observation that a Bvg+ phase-locked B. bronchiseptica mutant was indistinguishable from the wild type in its ability to establish a persistent respiratory infection in rabbits and rats (P. A. Cotter and J. F. Miller, Infect. Immun. 62:3381-3390, 1994; B. J. Akerley, P. A. Cotter, and J. F. Miller, Cell 80:611-620, 1995). To directly address the role of Bvg-mediated signal transduction in B. pertussis pathogenesis, we constructed Bvg+ and Bvg- phase-locked mutants and compared them with the wild type for their ability to colonize the respiratory tracts of mice. Our results show that the Bvg+ phase of B. pertussis is necessary and sufficient for respiratory infection. By constructing a strain with a deletion in the bvgR regulatory locus, we also show that ectopic expression of Bvg- phase phenotypes decreases the efficiency of colonization, underscoring the importance of Bvg-mediated repression of gene expression in vivo. Finally, we show that the virulence defect present in strain SK6 cannot be attributed to the vrg6 mutation. These data contradict an in vivo role for the Bvg- phase of B. pertussis.
Animals↗
Fas (CD95)-dependent cell-mediated immunity to Listeria monocytogenes.
Two distinct and complementary pathways, one mediated by perforin and the other dependent upon CD95 (Fas), effect cell-mediated cytotoxicity. We examined the relative roles of these pathways in host defenses against the intracellular bacterial pathogen Listeria monocytogenes by using murine listeriosis as a model system. Mice which lacked both perforin and Fas (P0L0) were generated, and their responses to primary and secondary listeriosis were compared to those of wild-type (WT), Fas-deficient (L0), and perforin knockout (P0) mice. Relative to WT mice during primary listeriosis, P0 mice exhibited a reduced capacity to clear the infection from their spleens but not their livers whereas L0 mice had elevated bacterial titers in their livers and a modestly increased titer in their spleens. In contrast, bacterial titers in P0L0 mice were increased approximately 50- to 560-fold in their spleens and 230- to 1, 000-fold in their livers; eventual clearance of listeriae from both organs was significantly delayed. Furthermore, the resistance of P0L0 mice to secondary listeriosis was significantly reduced in their spleens and livers compared to that of WT, P0, or L0 mice. In vitro experiments indicated that immune cytotoxic T lymphocytes (CTL) lysed L. monocytogenes-infected hepatocytes primarily via a Fas-dependent, perforin-independent mechanism. The absence of Fas severely abrogated the lysis of infected hepatocytes by immune CD8(+) CTL. Taken together, these results provide the first evidence for Fas-dependent CTL-mediated lysis of L. monocytogenes-infected hepatocytes and demonstrate complementary roles for Fas and perforin in host defenses against an intracellular bacterial pathogen.
Animals↗
CD4+ T cell help impairs CD8+ T cell deletion induced by cross-presentation of self-antigens and favors autoimmunity.
Self-antigens expressed in extrathymic tissues such as the pancreas can be transported to draining lymph nodes and presented in a class I-restricted manner by bone marrow-derived antigen-presenting cells. Such cross-presentation of self-antigens leads to CD8+ T cell tolerance induction via deletion. In this report, we investigate the influence of CD4+ T cell help on this process. Small numbers of autoreactive OVA-specific CD8+ T cells were unable to cause diabetes when adoptively transferred into mice expressing ovalbumin in the pancreatic beta cells. Coinjection of OVA-specific CD4+ helper T cells, however, led to diabetes in a large proportion of mice (68%), suggesting that provision of help favored induction of autoimmunity. Analysis of the fate of CD8+ T cells indicated that CD4(+) T cell help impaired their deletion. These data indicate that control of such help is critical for the maintenance of CD8+ T cell tolerance induced by cross-presentation.
Adoptive Transfer↗
Class I-restricted cross-presentation of exogenous self-antigens leads to deletion of autoreactive CD8(+) T cells.
In this report, we show that cross-presentation of self-antigens can lead to the peripheral deletion of autoreactive CD8(+) T cells. We had previously shown that transfer of ovalbumin (OVA)-specific CD8(+) T cells (OT-I cells) into rat insulin promoter-membrane-bound form of OVA transgenic mice, which express the model autoantigen OVA in the proximal tubular cells of the kidneys, the beta cells of the pancreas, the thymus, and the testis of male mice, led to the activation of OT-I cells in the draining lymph nodes. This was due to class I-restricted cross-presentation of exogenous OVA on a bone marrow-derived antigen presenting cell (APC) population. Here, we show that adoptively transferred or thymically derived OT-I cells activated by cross-presentation are deleted from the peripheral pool of recirculating lymphocytes. Such deletion only required antigen recognition on a bone marrow-derived population, suggesting that cells of the professional APC class may be tolerogenic under these circumstances. Our results provide a mechanism by which the immune system can induce CD8(+) T cell tolerance to autoantigens that are expressed outside the recirculation pathway of naive T cells.
Adoptive Transfer↗
Induction of a CD8+ cytotoxic T lymphocyte response by cross-priming requires cognate CD4+ T cell help.
Class I-restricted presentation is usually associated with cytoplasmic degradation of cellular proteins and is often considered inaccessible to exogenous antigens. Nonetheless, certain exogenous elements can gain entry into this so-called endogenous pathway by a mechanism termed cross-presentation. This is known to be effective for class I-restricted cytotoxic T lymphocyte (CTL) cross-priming directed against a variety of exogenous tumor, viral, and minor transplantation antigens. The related effect of cross-tolerance can also effectively eliminate responses to selected self components. In both cases, this presentation appears to require the active involvement of a bone marrow-derived antigen presenting cell (APC). Here, we show that CTL induction by cross-priming with cell-associated ovalbumin requires the active involvement of CD4+ helper T cells. Importantly, this CD4+ population is only effective when both the helper and CTL determinants are recognized on the same APC. Moreover, we would argue that the cognitive nature of this event suggests that the CD4+ T cell actively modifies the APC, converting it into an effective stimulator for the successful priming of the CTL precursor.
Animals↗
T cell tolerance and autoimmunity.
Many T cells with auto-aggressive potential are deleted in the thymus. Although some of these escape to the general circulation, they do not usually damage organs such as the pancreas. To investigate the mechanisms preventing autoimmunity, we generated transgenic mice expressing known genes under the control of various promoters. We found that the occurrence of autoaggression depended on factors such as the precursor frequency of responding T cells, their state of activation, their accessibility to the autoantigen, the physicochemical properties of the autoantigen, the possibility of priming by environmental antigens which mimic the target antigen, and some inflammatory reaction in the target site.
Animals↗
Dilute topical proparacaine for pain relief after photorefractive keratectomy.
PURPOSE: The purpose of the study is to determine whether there is a nonanesthetic and nontoxic concentration of topical proparacaine that can be applied repeatedly to the cornea to reduce pain after photorefractive keratectomy (PRK). METHODS: Part I: To determine a nonanesthetic concentration, the corneal sensitivity of 50 healthy volunteers was assessed using aesthesiometry before and after a drop of either 0.01%, 0.025%, 0.05%, 0.1%, or 0.2% topical proparacaine. Ten volunteers similarly were tested with multiple doses of 0.05% proparacaine. To evaluate toxicity, ten healthy volunteers self-administered 0.05% proparacaine to one eye and placebo to the other eye every 15 minutes for 12 hours on day 1 and every hour for 12 hours on days 2 through 7. Subjects were assessed throughout the week using visual acuity, slitlamp examination, aesthesiometry, and ultrasonic pachometry. Part II: In a prospective, double-masked study, 34 patients who underwent PRK (48 eyes) self-administered either topical 0.05% proparacaine or placebo for 1 week after PRK as needed to reduce pain. Patients recorded their pain score before and after drop use and answered a pain-relief questionnaire. RESULTS: Part I: Proparacaine concentrations greater than or equal to 0.1% eliminated sensation from some corneas; concentrations of less than or equal to 0.05% were never fully anesthetic. No corneal toxicity was observed except for some minimal punctate staining in both treatment and placebo eyes. Part II: Patients in the treatment group had significantly more pain relief (P < 0.001) for a longer period (P < 0.001) than did patients in the control group. Average change in pain score was significantly greater in the treatment group (P < 0.002). No significant difference in the number of days needed to reach complete epithelial healing was found between the two groups (P < 0.18). CONCLUSIONS: Dilute (0.05%) topical proparacaine is nonanesthetic and nontoxic, and can be used safely for at least 1 week to reduce pain after PRK.
Administration, Topical↗
A mutation in the Bordetella bronchiseptica bvgS gene results in reduced virulence and increased resistance to starvation, and identifies a new class of Bvg-regulated antigens.
The Bordetella BvgAS signal-transduction system has traditionally been viewed as mediating a transition between two distinct phenotypic phases: the Bvg+ phase, characterized by the expression of adhesins and toxins, and the Bvg-phase, characterized by motility in Bordetella bronchiseptica and by the expression of vrg loci in Bordetella pertussis. In B. bronchiseptica, the Bvg+ phase is necessary and sufficient for respiratory tract colonization whereas the Bvg phase is required for growth under nutrient-limiting conditions. This report describes the characterization of a mutant that is locked in a Bvg-intermediate (Bvg[i]) phase. The mutation conferring this phenotype, designated bvgS-I1, results in a threonine-to-methionine substitution near the primary site of phosphorylation in BvgS. Compared to its Bvg+-phase-locked parent, the Bvg(i) mutant displays increased resistance to nutrient limitation and reduced virulence. Molecular analyses indicate that the mutant has lost the ability to express a subset of Bvg+-phase factors and has gained the ability to express factors unique to the Bvg(i) phase. Although identified by mutation, this work indicates that the Bvg(i) phase is expressed by wild-type B. bronchiseptica in response to certain (semi-modulating) environmental conditions. The identification of Bvg(i)-specific antigens suggests the existence of a new class of Bvg-regulated genes. We hypothesize that BvgAS is capable of mediating the expression of a spectrum of phenotypic phases in response to the various environments encountered as Bordetella travels within and between mammalian hosts.
Amino Acid Sequence↗