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B Charlton

Publications and source records attributed to B Charlton.

At least 19 recordsLinked to original sources
PubMed1998

Prevention of Th2-mediated murine allergic airways disease by soluble antigen administration in the neonate.

It has been demonstrated recently that neonatal antigen administration in the mouse can lead to priming for Th2-mediated immune responses. This observation has important implications for the development of vaccination strategies in humans, particularly for individuals who may be predisposed to atopy or asthma. In this paper it is shown that although i.p. administration of antigen (100 microg) in adjuvant to the neonate does indeed prime for Th2-mediated disease in mice [allergic airways disease (AAD)], when the same relatively low dose of antigen is given in soluble form no priming occurs. Further, administration of a larger dose of soluble antigen (1 mg) actually prevents the ability to prime for a Th2 response subsequently and so prevents the induction of AAD. Protection from disease was associated with evidence of functional inactivation of both Th1 and Th2 ovalbumin-specific T cells. In contrast, administration of a very low dose of antigen (10 microg) primed for a Th2 response in a similar fashion to antigen in adjuvant. We suggest that the adjuvant lowers the "effective" dose of antigen administered in the neonate and thereby primes for Th2-type immune responses. These findings demonstrate that neonatal antigen administration can inhibit Th2-mediated diseases, such as AAD, but the dose of antigen may be critical to avoid predisposition to disease.

Animals↗
PubMed1998

Th1 unresponsiveness can be infectious for unrelated antigens.

CD4+ T cells may be assigned a functional status (Th1 or Th2) according to the cytokines they produce including IL-2, IFN-gamma and IL-4. Th1 and Th2 CD4+ T cells deliver different isotype-switching signals to antigen-specific B cells which bias the serum Ig isotypes. The stimulation of Th1 or Th2 responses is influenced by adjuvants and administration of antigen in IFA results in Th1 unresponsiveness as evidenced by: (i) reduced T cell proliferation to antigen; (ii) reduced IFN-gamma production in response to antigen; and (iii) reduced IgG2a isotype antigen-specific antibodies following antigen/CFA challenge. The impact of established human gamma globulin (HGG) specific Th1 unresponsiveness on subsequent immunization with an unrelated antigen, human serum albumin (HSA) in Th1-inducing CFA was then examined. When subsequently challenged with a mixture of HSA and HGG in CFA the HGG-specific Th1 unresponsiveness was infectious and dominant, preventing the induction of a Th1 response to HSA. Reduced T cell proliferation, IFN-gamma production and IgG2a antibody were consequently observed in response to HSA. The HGG-specific Th1 unresponsiveness was not infectious when HGG/CFA and HSA/CFA were administered at separate sites. This demonstrates that antigen-specific Th1 unresponsiveness can be infectious for new, molecularly unrelated antigens and supports studies showing that Th1-mediated autoimmune diseases such as experimental allergic encephalomyelitis (EAE) and diabetes can be ameliorated using antigens molecularly distinct from the disease-inducing immunogen.

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PubMed1997

Development of insulitis and diabetes in B cell-deficient NOD mice.

Insulin-dependent diabetes mellitus (IDDM) is believed to be an autoimmune disease that results from autoimmune destruction of the insulin-secreting beta-cells of the pancreas. In addition to a lymphocytic infiltration (insulitis) of the islets, patients with IDDM have autoantibodies directed against the components of the islet cells. Several beta-cell proteins have been identified as candidate autoantigens. The non-obese diabetic (NOD) mouse is a murine model for spontaneous IDDM. It is generally accepted that IDDM in patients and NOD mice results from the T lymphocyte-mediated destruction of beta-cells. However, the direct role of B lymphocytes in the disease process has not yet been clarified. To test directly the role of B cells in IDDM, we have generated B cell-deficient NOD mice by backcrossing the microMT-/- B cell 'knockout mice' onto the NOD background. The mice had no evidence of functional B cells as determined by flow cytometry and antibody production. We show that two out of seven of these mice developed insulitis and diabetes. These results suggest that despite an absence of B cells some NOD mice can still develop insulitis and diabetes.

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PubMed1997

Diabetes results from a late change in the autoimmune response of NOD mice.

IDDM in the NOD mouse is the result of a chronic autoimmune process. NOD mice are shown to express benign autoimmunity that converts to a state of malignant autoimmunity and the development of IDDM. Young disease-prone NOD mice are in a state of benign autoimmunity that is correlated with a non-destructive response to islet tissue and the preservation of insulin-containing beta-cells. A proportion of mice with benign autoimmunity convert to having malignant autoimmunity. Clinical diabetes is diagnosed approximately 3 weeks from the development of malignant autoimmunity which is correlated with a destructive response to grafted islet tissue and extensive beta-cell destruction. We conclude that the development of clinical disease is correlated with a change in the state of autoimmunity, that is, from benign to malignant autoimmunity.

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PubMed1996

CD4+ T cell mediated destruction of xenografts within cell-impermeable membranes in the absence of CD8+ T cells and B cells.

Xenogeneic cells encapsulated in cell-impermeable diffusion chambers die within 3 weeks when implanted into immunocompetent animals but not when implanted into immunodeficient animals. To determine which cells are necessary for this observation, we depleted normal mice in vivo of either CD4+ or CD8+ T cells using monoclonal antibodies. We also reconstituted the immune system of athymic CBA mice (T-lymphocyte deficient) and C.B17 SCID mice (T- and B-lymphocyte deficient) with different cell subsets from normal CBA and BALB/C mice, respectively. Depleted or reconstituted mice were implanted with a diffusion chamber containing COS (monkey kidney) cells. Membrane enclosed xenografts survived in CD4+ T cell depleted mice but not in CD8+ T cell depleted or nondepleted control mice. Encapsulated xenografts survived when implanted into either athymic or SCID mice but were destroyed in reconstituted athymic and SCID mice. Furthermore, encapsulated xenogeneic cells were destroyed in athymic or SCID mice reconstituted with CD4+ cell preparations depleted of CD8+ cells and/or B cells. In contrast, encapsulated xenogeneic cells were not destroyed in athymic or SCID mice reconstituted with CD8+ cell preparations depleted of CD4+ cells. These studies highlight the critical role of CD4+ T cells, in the absence of CD8+ cells and B cells, in the processes leading to the ultimate destruction of encapsulated xenografts. Because of the use of cell-impermeable membranes in these studies, the most likely involvement of CD4+ T cells is in the indirect antigen recognition by these cells and subsequent stimulation of inflammatory cells.

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PubMed1996

Immune regulation in type 1 diabetes.

The non-obese diabetic (NOD) mouse is an animal model of insulin-dependent diabetes mellitus (IDDM) that shows many of the characteristics of human IDDM. In the NOD model, there exists a discrepancy between the onset of insulitis and diabetes suggesting the potential existence of some form of immune regulation that delays beta cell destruction. Our transfer system using NOD-scid/scid (NOD-scid) mice as recipients of donor NOD cells suggested that immune regulatory cells exist in the periphery of NOD mice, not in the islets. These regulatory cells are considered to be memory CD4+ cells which show a Th2 (or Th zero) type cytokine profile following activation in vitro. The function of the memory CD4+ cells seems to change from protective to pathogenic as the disease progresses. Moreover, cytokine profiles of this CD4+ CD45RBlow (memory) population shifted from a Th2 (or Th zero) to a Th1 type response coincident with the onset of hyperglycaemia. These data suggest that the progression of NOD disease from insulitis to frank hyperglycaemia is under the control of CD4+ CD45RBlow immune 'regulatory' cells.

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PubMed1996

Monoclonal T cells identified in early NOD islet infiltrates.

To examine the hypothesis that a single initiating antigen was recognized by a monoclonal T cell population leading to subsequent inflammatory insulitis in non-obese (NOD) mouse islets, we examined the T cell receptor TCR V beta repertoire of islet-infiltrating T cells in very young (2-week-old) NOD mice. In independent experiments, we repeatedly identified one monoclonal TCR V-beta 8.2 gene product expressed by T lymphocytes infiltrating the islets of NOD mice at 2 weeks of age. The resultant inflammatory response quickly obscures the monoclonal nature of the initiating event. These data suggest that autoimmune diabetes in NOD mice may be initiated by recognition of a single autoantigen.

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PubMed1996

Pathogenic and protective roles of CD45RB(low) CD4+ cells correlate with cytokine profiles in the spontaneously autoimmune diabetic mouse.

The adoptive transfer of splenocytes from diabetic NOD mice to NOD-scid/scid (NOD-scid) recipients results in diabetes. This model was used to test the effect of cotransfer of splenocyte subsets from young nondiabetic NOD mice. As shown previously in other NOD models, the CD4+ subset from young nondiabetic mice significantly delayed the onset of diabetes in splenocyte cotransfers (P < 0.001). The data presented here showed that the development of diabetes in NOD-scid recipients correlated with a rapid increase in peripheral CD45RB(low) CD4+ cells. However, the CD45RB(low) subset of CD4+ cells from young nondiabetic mice protected from diabetes transfer in this model. We therefore examined whether CD45RB(low) CD4+ cells from diabetic mice were pathogenic rather than protective. CD45RB(low) CD4+ splenocytes from diabetic NOD mice were transferred along with CD8+ splenocytes from diabetic mice into NOD-scid recipients, and all of the recipients became diabetic within 5 weeks posttransfer. In contrast, no recipients (0 of 10) of CD45RB(high) CD4+ cells along with CD8+ splenocytes from diabetic mice became diabetic within 5 weeks posttransfer (P < 0.001). A correlate for the difference between CD45RB(low) CD4+ cells from diabetic NOD mice and CD45RB(low) CD4+ cells from nondiabetic mice, which showed protective effect in splenocyte cotransfers, was found in cytokine production after stimulation with anti-CD3 antibodies in vitro. CD45RB(low) CD4+ cells from diabetic mice showed a significantly higher ratio (approximately fivefold) of gamma-interferon (IFN-gamma) to interleukin (IL)-4 when compared with CD45RB(low) CD4+ cells from nondiabetic mice (P < 0.001). In conclusion, the function of the CD45RB(low) population of CD4+ cells changes from a protective to a pathogenic one during the development of disease in the NOD mouse. This change in function correlates with cytokine production in vitro; increased IFN-gamma-to-IL-4 ratio is associated with pathogenic potential and occurs coincident with (or after) the onset of diabetes.

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PubMed1996

Beta-cell destruction may be a late consequence of the autoimmune process in nonobese diabetic mice.

The NOD mouse is an animal model of IDDM that shows many of the characteristics of human IDDM. It has been proposed that beta-cell destruction in IDDM progresses over time in a linear manner. Recently, we and others have demonstrated that T helper type 1 (Th1) cells have pathogenic roles in the NOD model and proposed that cytokine balances change as the disease progresses. However, it has not been demonstrated how or when the cytokine balances change or how the beta-cell destruction progresses. We have recently demonstrated that the cytokine profiles of CD45RB(low) CD4+ cells correlate either with their pathogenic or with their protective roles in the NOD mouse. To further analyze this apparent correlation between the shift in cytokine level and IDDM, we examined the anti-CD3-induced cytokine profiles of this subset from NOD mice of various ages compared with that from age-matched I-Ak transgenic NOD and BALB/c mice as controls. A significantly higher ratio of anti-CD3-induced interferon-gamma/interleukin-4 was found in diabetic NOD mice (P < 0.0001) but not in age-matched nondiabetic NOD mice. This cytokine ratio did not change significantly until the onset of diabetes in NOD mice. Based upon these results, we propose that IDDM in the NOD mouse progresses as a predominant inflammatory beta-cell dysfunction without actual beta-cell destruction until late in the disease process. This supports the possibility that late-stage immunotherapy may preserve islet beta-cell mass.

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PubMed1995

The Th1/Th2 balance in autoimmunity.

The study of autoimmune disease in the context of T-helper type 1 (Th1) and T-helper type 2 (Th2) CD4+ T-cell responses demonstrates that the relative contribution of either T-cell type to the development of a particular autoimmune response can influence whether or not this response leads to clinical disease. Moreover, this influence can be quite different depending on whether the particular disease process is cell mediated or antibody mediated. Recent studies have demonstrated that the development of Th1 and Th2 responses may be significantly influenced by the costimulatory molecules recognized by responding CD4 T cells, and by other undefined factors in the genetic background. It has also been demonstrated that autoreactive Th2 CD4+ cells can regulate the activity of disease-causing Th1 CD4+ T cells in vivo. Control of autoimmune disease may thus be achieved by procedures that regulate the relative contribution of Th1/Th2 CD4 T cells to an autoimmune response.

Animals↗
PubMed1995

Islet-infiltrating lymphocytes from prediabetic NOD mice rapidly transfer diabetes to NOD-scid/scid mice.

In an effort to study the development of diabetes in NOD mice, our laboratory developed a novel adoptive transfer model using NOD-scid/scid (NOD-scid) mice as recipients of islet-infiltrating lymphocytes from donor prediabetic female NOD mice. We first confirmed previous results that demonstrated that splenocytes of diabetic and prediabetic female NOD mice could transfer diabetes to NOD-scid mice. We demonstrated that the kinetics of disease transfer were dependent on the age of transferred lymphocytes and reiterated the kinetics of diabetes in conventional female NOD mice. We then demonstrated that islet-infiltrating lymphocytes from prediabetic female NOD mice could transfer diabetes. In contrast with the age-dependent transfer of diabetes seen using splenocytes, islet-infiltrating lymphocytes obtained from prediabetic female NOD mice aged > or = 40 days rapidly transferred diabetes to NOD-scid recipients. The time required to transfer insulin-dependent diabetes mellitus (IDDM) using islet-infiltrating lymphocytes from young prediabetic mice (25 +/- 9 days) was not statistically different from the time required to transfer IDDM using splenocytes from overtly diabetic mice (32 +/- 5 days). Cotransfer of splenocyte cells or CD4+, but not CD8+ spleen cells, from 60- to 80-day-old prediabetic female NOD mice together with either splenocytes from diabetic mice or islet-infiltrating lymphocytes from prediabetic NOD mice delayed the rapid transfer of IDDM, suggesting that CD4+ cells mediated immunoregulation. Use of the NOD-scid islet-infiltrating lymphocyte-adoptive transfer model should help elucidate the pathophysiology of the early inflammatory events leading to insulitis and subsequent beta-cell destruction.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1994

CD4-positive/heat-stable antigen-positive thymocytes cause graft-versus-host disease across non-major histocompatibility complex incompatibilities.

Single-positive thymocytes are the immediate precursors of peripheral recent thymic emigrants (RTE) which develop into mature peripheral T cells. The functional ability of RTE is unclear but their state of differentiation may be relevant to the development of tolerance to peripheral "self" antigens. Since RTE are difficult to analyze, precursor CD4+/8- thymocytes were assessed in a model in vivo to determine their functional capability and their susceptibility to tolerance induction. The ability of both heat-stable antigen-positive (HSA+) (immature) and HSA- (mature) single-positive thymocytes to cause graft-versus-host disease (GVHD) across non-major histocompatibility complex differences were examined. Both HSA- and HSA+ CD4+/8- thymocytes from C3H mice caused lethal GVHD in AKR recipients as did CD4+ peripheral T cells in controls. Further, neonatal C3H thymocytes also caused lethal GVHD in AKR recipients. Since CD4+/8- thymocytes are the precursors of RTE, these results suggest that RTE are not susceptible to tolerance induced to "minor" antigens and may have a normal immune function in vivo. This would suggest that peripheral tolerance may be dependent upon the manner of antigen presentation rather than T cell maturity.

Animals↗
PubMed1994

Prevention of diabetes and insulitis by neonatal intrathymic islet administration in NOD mice.

The murine model of human insulin dependent diabetes mellitus (IDDM), the non-obese diabetic (NOD) mouse, develops a T cell-dependent destruction of pancreatic islets. While the target antigens are unknown, there is clearly a lack of tolerance to them. Neonatal intrathymic (i.t.) antigen injection has been successfully employed to prevent insulitis in BB rats but previous i.t. islet antigen studies in NOD mice were done on older mice. We have injected syngeneic islets into the thymus of NOD mice at birth and found that diabetes and insulitis can be completely prevented by this procedure. The effect is islet antigen-specific since other T cell responses, including autoimmune salivary infiltration, ard unaffected. Furthermore, contrary to previous studies, cyclophosphamide administration was unable to induce diabetes in treated mice which suggests that deletion or anergy might be the mechanism by which neonatal intrathymic islet injection protects from disease. However, anti-islet antigen antibodies were still present in these mice which suggests that the mechanism of disease protection may be more complex.

Animals↗
PubMed1994

Mechanisms of transplantation tolerance.

Transplantation tolerance, the long-term acceptance of grafted tissue in the absence of continuous immunosuppression, remains an elusive goal in humans, but it has been achieved in animal models using numerous approaches. The mechanisms behind graft acceptance vary according to the means used to create the state of acceptance. Several major mechanisms can now be recognized. While thymic deletion of T cells appears to be a mainstay of self-tolerance, its role in transplantation tolerance now seems to be less significant. In contrast, extrathymic mechanisms of transplantation tolerance seem to be major factors in long-term graft acceptance. If donor antigens are presented in a nonimmunogenic manner on the graft, e.g. due to modification of graft tissue by culture, peripheral T cells of the recipient may ignore the graft. Alternatively, nonstimulatory presentation of donor antigens on graft tissue can induce a state of unresponsiveness in recipient T cells, i.e. anergy, rather than activating them to destroy the graft. Suppression mechanisms also operate to control graft rejection and may be specific or nonspecific in nature. Specific suppression mechanisms might act in an idiotype or antigen-specific fashion, and evidence is accumulating that this may be mediated through the elaboration of cytokines. Donor antigen-specific T cells may be activated to produce "protective" cytokines which then regulate the generation of destructive T cells. Future therapies will be aimed at affecting graft acceptance through these peripheral mechanisms.

Animals↗
PubMed1993

Failure of a protective major histocompatibility complex class II molecule to delete autoreactive T cells in autoimmune diabetes.

The association of major histocompatibility complex genes with autoimmune diseases is firmly established, but the mechanisms by which these genes confer resistance or susceptibility remain controversial. The controversy extends to the nonobese diabetic (NOD) mouse that develops disease similar to human insulin-dependent diabetes mellitus. The transgenic incorporation of certain class II major histocompatibility complex genes protects NOD mice from diabetes, and clonal deletion or functional silencing of autoreactive T cells has been proposed as the mechanism by which these molecules provide protection. We show that neither thymic deletion nor anergy of autoreactive T cells occurs in NOD mice transgenic for I-Ak. Autoreactive T cells are present, functional, and can transfer diabetes to appropriate NOD-recipient mice.

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