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Biomedical subjects

A N McKenzie

Publications and source records attributed to A N McKenzie.

At least 19 recordsLinked to original sources
PubMed2001

IL-13 overexpression predisposes to anaphylaxis following antigen sensitization.

Anaphylaxis represents an extreme form of allergic reaction. This acute-phase component of allergy and asthma is triggered by allergen-induced degranulation of mast cells following the cross-linking of cell surface-bound, allergen-specific IgE, resulting in the liberation of inflammatory mediators and the development of bronchoconstriction. We used IL-13 transgenic mice to investigate the role of this Th2 cell-derived cytokine in the onset of allergic disease. Strikingly, IL-13-transgenic mice were highly predisposed to fatal anaphylaxis following Ag sensitization. This response correlated with substantially elevated levels of circulating Ag-specific IgE, mast cell degranulation, and histamine release. Furthermore, allergen exposure also induced phenotypic changes typical of asthma, including pulmonary fibrosis, goblet cell hyperplasia, elevated Th2 cytokines, eosinophilia, and airways occluded by mucus and Charcot-Leyden crystals. Expression of IL-4 was not required for the induction of IgE-mediated responses. These data represent the first characterization of a functional role for IL-13-induced IgE in the generation of immediate hypersensitivity reactions and highlight the importance of IL-13 in the development of the symptoms of atopy. The systemic regulation of this response makes these mice an important resource for studying atopic responses.

Anaphylaxis↗
PubMed2001

Disrupting Il13 impairs production of IL-4 specified by the linked allele.

Interleukin 13-deficient (IL-13-/-) mice express a defect in priming for IL-4 production that is not corrected by adding IL-13 to the priming culture. This is partly accounted for by the consumption of IL-4 without endogenous replacement during culture of IL-13-/- CD4+ T cells. We examined cells from mice in which disrupted Il13 was linked to wild-type Il4 on one chromosome and wild-type Il13 was linked to a "knocked-in" green fluorescent protein (Gfp) gene in the Il4 locus. Our results show that the deficit in IL-4 production was due, at least in part, to a cis effect, in which disrupted Il13 diminished IL-4 production from the linked Il4 gene.

Alleles↗
PubMed2001

Distinct spatial requirement for eosinophil-induced airways hyperreactivity.

T helper (Th)-2-derived cytokines and their involvement in the recruitment and activation of inflammatory cells crucially orchestrate asthma pathogenesis. A notable cellular component of this allergy-induced inflammation is the eosinophil. However, whether the eosinophil is an obligatory mediator for enhancing airways hyperreactivity (AHR) to cholinergic stimuli, a watershed of the asthmatic lung, is somewhat controversial. In this investigation we have endeavoured to define the spatial requirements for IL-4 and IL-13, and the downstream effector molecules, IL-5 and the CC chemokine eotaxin, for the recruitment of eosinophils and the development of AHR in a murine model of allergic pulmonary disease. These studies are of particular importance considering clinical trials, with either the soluble IL-4Ralpha subunit or a humanized anti-IL-5 antibody, are being conducted. Interestingly, our studies show that depletion of both IL-4 and IL-13 is necessary to ablate pulmonary eosinophilia and AHR, and that this may be attributed to the role these cytokines play in regulating the expression of the eosinophil- activating molecules, IL-5 and eotaxin. While it is clear that depletion of IL-5 diminishes pulmonary eosinophilia, we demonstrate in BALB/c mice that a deficiency in both IL-5 and eotaxin is necessary to abolish both the trafficking of eosinophils to the lung and AHR. However, in contrast to the neutrophil-rich inflammation observed in mice deficient in both IL-4 and IL-13, inflammation per se in mice deficient in both IL-5 and eotaxin is significantly attenuated. This suggests that asthma immunotherapy may be better directed towards the eosinophil- activating molecules IL-5 and eotaxin, rather than towards pleiotrophic molecules such IL-4 and IL-13, which are additionally important in modulating alternative inflammatory responses.

Animals↗
PubMed2000

Integrated signals between IL-13, IL-4, and IL-5 regulate airways hyperreactivity.

In this investigation, we have examined the integrated relationship between IL-13, IL-4, and IL-5 for the development of airways hyperreactivity (AHR) in a model of asthma in BALB/c mice. Sensitization and aeroallergen challenge of both wild-type (WT) and IL-13 gene-targeted (IL-13-/-) mice induced allergic disease that was characterized by pulmonary eosinophilia and AHR to beta-methacholine. Although these responses in IL-13-/- mice were heightened compared with WT, they could be reduced to the level in nonallergic mice by the concomitant neutralization of IL-4. Mice in which both IL-4 and IL-13 were depleted displayed a marked reduction in tissue eosinophils, despite the development of a blood eosinophilia. Similar neutralization of IL-4 in WT mice only partially reduced AHR with no effect on tissue eosinophilia. In addition, neutralization of IL-5 in IL-13-/- mice, but not in WT mice, inhibited AHR, suggesting that tissue eosinophilia is linked to the mechanism underlying AHR only in the absence of IL-13. Additionally, mucus hypersecretion was attenuated in IL-13-/- mice, despite the persistence of AHR. Taken together, our data suggest both a modulatory role for IL-13 during sensitization and a proinflammatory role during aeroallergen challenge. The latter process appears redundant with respect to IL-4.

Adjuvants, Immunologic↗
PubMed2000

T1/ST2-deficient mice demonstrate the importance of T1/ST2 in developing primary T helper cell type 2 responses.

We have generated mice with a deficiency in T1/ST2 expression to clarify the roles of T1/ST2 in T helper cell type 2 (Th2) responses. Using immunological challenges normally characterized by a Th2-like response, we have compared the responses of T1/ST2-deficient mice with those generated by wild-type mice. Using a primary pulmonary granuloma model, induced with Schistosoma mansoni eggs, we demonstrate that granuloma formation, characterized by eosinophil infiltration, is abrogated in T1/ST2-deficient mice. Furthermore, we clearly demonstrate that in the absence of T1/ST2 expression, the levels of Th2 cytokine production are severely impaired after immunization. Thus, in a secondary pulmonary granuloma model, draining lymph node cells from the T1/ST2-deficient animals produced significantly reduced levels of IL-4 and IL-5, despite developing granulomas of a magnitude similar to those of wild-type mice and comparable antigen-specific immunoglobulin isotype production. These data clearly demonstrate that T1/ST2 expression plays a role in the development of Th2-like cytokine responses and indicate that effector functions are inhibited in its absence.

Animals↗
PubMed2000

Schistosome infection of transgenic mice defines distinct and contrasting pathogenic roles for IL-4 and IL-13: IL-13 is a profibrotic agent.

Experimental Schistosoma mansoni infections of mice lead to a dynamic type 2 cytokine-mediated pathological process. We have used IL-4-deficient, IL-13-deficient, and IL-4/13-deficient mice to dissect the role of these cytokines in the development of immune response and pathology following S. mansoni infection. We demonstrate that while both of these cytokines are necessary to develop a robust Th2 cell-driven, eosinophil-rich granuloma response, they also perform disparate functions that identify novel sites for therapeutic intervention. IL-13-deficient mice demonstrated significantly enhanced survival following infection, which correlated with reduced hepatic fibrosis. In contrast, increased mortality was manifest in IL-4-deficient and IL-4/13-deficient mice, and this correlated with hepatocyte damage and intestinal pathology. Therefore, we demonstrate that during a dynamic type 2 cytokine disease process IL-13 is detrimental to survival following infection, whereas IL-4 is beneficial.

Animals↗
PubMed2000

IL-13 is a susceptibility factor for Leishmania major infection.

Leishmania major infection is useful as an experimental model to define factors responsible for the development and maintenance of Th cell immune responses. Studies using inbred mouse strains have identified that the Th1 response characteristic of C57BL/6 mice results in healing, whereas BALB/c mice fail to control the infection due to the generation of an inappropriate Th2 response. We now demonstrate that IL-13 is a key factor in determining susceptibility to L. major infection. Overexpression of IL-13 in transgenic mice makes the normally resistant C57BL/6 mouse strain susceptible to L. major infection even in the absence of IL-4 expression. This susceptibility correlates with a suppression of IL-12 and IFN-gamma expression. Furthermore, using BALB/c mice deficient in the expression of IL-4, IL-13, or both IL-13 and IL-4, we demonstrate that IL-13-deficient mice are resistant to infection and that there is an additive effect of deleting both IL-4 and IL-13.

Animals↗
PubMed2000

Regulation of T helper type 2 cell immunity by interleukin-4 and interleukin-13.

Type 2 cytokine responses are typical of immune reactions to parasitic helminth infections, allergies, and asthma, and are characterised by the production of the cytokines interleukin (IL)-4, IL-5, IL-9, and IL-13 by subsets of T helper type 2 (Th2) cells. These cytokines form a complex network of molecular and cellular interactions that mediate protective immunity to worm infection, but also induce inappropriate inflammatory responses to allergic challenge. Although considerable attention has been given to the roles played by IL-4 in Th2 responses, the identification of the related cytokine IL-13 has led to a re-evaluation of how these two molecules combine in the generation of Th2 immunity. Recent reports have highlighted that in certain challenges, IL-4 and IL-13 act in combination to ensure the rapid onset of a Th2-like response. However, these studies have also identified specific responses that are attributable to the individual cytokines. For example, IL-13 appears to play a more dominant role than IL-4 in the expulsion of certain gastrointestinal parasites. In contrast, following schistosome infection, IL-13 induces a detrimental hepatic fibrosis, while IL-4 protects against endotoxemia. These results emphasise the complexity of the cytokine network, and highlight the care that needs to be taken when designing therapeutic intervention.

Asthma↗
PubMed1999

Simultaneous disruption of interleukin (IL)-4 and IL-13 defines individual roles in T helper cell type 2-mediated responses.

Using a single vector targeting strategy, we have generated mice with a combined deficiency of interleukin (IL)-4 and IL-13 to clarify their roles in T helper type 2 (Th2) cell responses. Using immunological challenges normally characterized by a Th2-like response, we have compared the responses of the double-deficient mice with those generated by wild-type, IL-4-deficient, and IL-13-deficient mice. Using a pulmonary granuloma model, induced with Schistosoma mansoni eggs, we demonstrate that although eosinophil infiltration, immunoglobulin E, and IL-5 production are reduced in the IL-4-deficient mice and IL-13-deficient mice, they are abolished only in the combined absence of both cytokines. Furthermore, IL-4/13-deficient animals are severely impaired in their ability to expel the gastrointestinal nematode Nippostrongylus brasiliensis. Unexpectedly, N. brasiliensis-infected IL-4/13-deficient mice developed elevated IL-5 and eosinophilia, indicating that compensatory mechanisms exist for the expression of IL-5, although serum IgE remained undetectable. IL-4/13-deficient mice default to a Th1-like phenotype characterized by the expression of interferon gamma and the production of IgG2a and IgG2b. We conclude that IL-4 and IL-13 cooperate to initiate rapid Th2 cell-driven responses, and that although their functions overlap, they perform additive roles.

Animals↗
PubMed1998

Interleukin (IL)-4-independent induction of immunoglobulin (Ig)E, and perturbation of T cell development in transgenic mice expressing IL-13.

Recent studies using interleukin (IL)-4-deficient animals have highlighted the existence of IL-4-independent immunoglobulin (Ig)E induction. We have established transgenic mice expressing IL-13 from a transgene comprising a genomic fragment containing the IL-13 gene and the human CD2 locus control region. The transgenes were expressed in lymphoid tissues and induced by T cell activators, suggesting regulation by elements of the IL-13 promoter. IL-13 transgenic lines expressed 10-100-fold higher levels of serum IgE than their littermate controls, but had normal levels of other serum Ig isotypes. Elevated IgE levels were also detected in sera from IL-4-deficient mice carrying IL-13 transgenes, indicating that IL-4 is not required for IL-13-induced IgE expression in the mouse. Expression of IL-13 also perturbed the development of thymocytes. Although thymocyte development was normal up to 4 wk of age, thymocyte number decreased dramatically thereafter, reaching 10% of normal by 10 wk, and despite normal size and appearance, histological examination demonstrated that transgenic thymi contained only small foci of thymocytes. The reduction in thymocyte number was due mainly to a depletion of CD4(+)CD8(+) thymocytes, and did not affect significantly the composition of peripheral T cell populations. These data indicate that expression of IL-13 transgenes in vivo can regulate IgE production in the mouse, and that IL-13 may also influence thymocyte development.

Animals↗
PubMed1998

A critical role for IL-13 in resistance to intestinal nematode infection.

Mice in which either the IL-4 or the IL-13 gene has been disrupted (IL-4 KO and IL-13 KO) were susceptible to infection with the intestinal nematode Trichuris muris, whereas their wild-type littermates were highly resistant and expelled the parasite. IL-4 KO mice showed diminished Th2-type responses with T. muris infection and also failed to produce parasite-specific IgG1 Abs. Although IL-13 KO mice made reduced Th2-type responses early in infection, they were capable of generating strong Th2-type responses at later time points and were unable to regulate the magnitude of their Ab isotype response. These results confirm the importance of IL-4 in resistance to T. muris and provide the first demonstration of an important role for IL-13 in resistance to helminth infection. The IL-13 KO mouse had a separate phenotype to that of the IL-4 KO mouse, suggesting that both IL-4 and IL-13 play important yet different roles in mediating immunity to intestinal helminths.

Animals↗
PubMed1998

A distinct role for interleukin-13 in Th2-cell-mediated immune responses.

Immune responses elicited by allergic reactions and parasitic worm infections are characterised by the induction of T helper 2 (Th2) cells. These cells secrete cytokines such as interleukin-4 (IL-4), IL-5 and IL-13, which induce the production of immunoglobulin E (IgE) and eosinophils [1,2]. Previous studies using gastrointestinal nematodes to elucidate the role of Th2-cell-mediated immune responses have demonstrated a causal relationship between T cells and worm expulsion (reviewed in [3]). Although it has been proposed that IL-4 played a central role in these responses, recent studies demonstrated that IL-4-/- mice expel the parasitic gastrointestinal nematode Nippostrongylus brasiliensis normally [4], suggesting that another T-cell mediator is required for efficient worm clearance. Using IL-13-/- mice, we have demonstrated that, unlike wild-type and IL-4-/- mice, the IL-13-/- animals failed to clear N. brasiliensis infections efficiently, despite developing a robust Th2-like cytokine response to infection. Furthermore, treatment of the IL-13-/- mice with exogenous IL-13 resulted in a reduction in the numbers of worms recovered. The IL-13-/- animals also failed to generate the goblet cell hyperplasia that normally occurs coincident with worm expulsion. This observation may link IL-13 with the production of intestinal mucus which is believed to facilitate worm expulsion. These data support a unique role for IL-13 in Th2-cell-mediated immune responses and demonstrate that IL-13 and IL-4 are not redundant.

Animals↗
PubMed1998

Impaired development of Th2 cells in IL-13-deficient mice.

We report that Th2 cell cultures generated using T cells or splenocytes from IL-13-deficient mice produce significantly reduced levels of IL-4, IL-5, and IL-10 compared with wild-type. In contrast, IL-4 and IL-5 production by mast cells stimulated in vitro with PMA, ionomycin, or IgE cross-linking are unaffected. In vitro Th2 cell differentiation cannot be rescued by the addition of exogenous factors, but in vivo antigen challenge and administration of IL-13 can increase Th2-like cytokine responses as can infection with the parasitic nematode Nippostrongylus brasiliensis. IL-13-deficient mice also have lower basal levels of serum IgE and biased antigen-specific immunoglobulin responses. Thus, IL-13 is an important regulator of Th2 commitment and may therefore play a central role in atopy and infectious diseases.

Animals↗
PubMed1996

An Mll-AF9 fusion gene made by homologous recombination causes acute leukemia in chimeric mice: a method to create fusion oncogenes.

Homologous recombination in embryonal stem cells has been used to produce a fusion oncogene, thereby mimicking chromosomal translocations that frequently result in formation of tumor-specific fusion oncogenes in human malignancies. AF9 sequences were fused into the mouse Mll gene so that expression of the Mll-AF9 fusion gene occurred from endogenous Mll transcription control elements, as in t(9;11) found in human leukemias. Chimeric mice carrying the fusion gene developed tumors, which were restricted to acute myeloid leukemias despite the widespread activity of the Mll promoter. Onset of perceptible disease was preceded by expansion of ES cell derivatives in peripheral blood. This novel use of homologous recombination formally proves that chromosomal translocations contribute to malignancy and provides a general strategy to create fusion oncogenes for studying their role in tumorigenesis.

Acute Disease↗
PubMed1995

The primary binding subunit of the human interleukin-4 receptor is also a component of the interleukin-13 receptor.

Interleukin (IL)-13 elicits a subset of the biological activities of the related IL-4. The basis of this functional similarity is that their specific cell-surface receptors (called IL-13R and IL-4R) are distinct, yet are complex and share a common subunit(s). The IL-4R primary binding subunit (called IL-4R alpha) does not by itself bind IL-13. We show that the ability of IL-13 to partially compete for IL-4 binding to some human cell types depended on co-expression of IL-4R and IL-13R. However, IL-13 binding was always associated with IL-4 binding. Hyper-expression of IL-4R alpha on cells expressing both IL-4R and IL-13R decreased their binding affinity for IL-4, abrogated the ability of IL-13 to compete for IL-4 binding, and yet had no effect on IL-13R properties. Anti-human IL-4R alpha monoclonal antibodies which blocked the biological function and binding of IL-4 also blocked the function and binding of IL-13. These data show that IL-4R alpha is a secondary component of IL-13R.

Animals↗
PubMed1993

Structural comparison and chromosomal localization of the human and mouse IL-13 genes.

The genomic structure of the recently described cytokine IL-13 has been determined for both human and mouse genes. The nucleotide sequence of a 4.6-kb DNA segment of the human gene is described. The human IL-13 gene (IL13) occurs as a single copy in the haploid genome and maps to human chromosome 5. A 4.3-kb DNA fragment of the mouse IL-13 gene (IL13) has been sequenced and found to occur as a single copy, mapping to mouse chromosome 11. Intrachromosomal mapping studies revealed that both genes contain four exons and three introns and show a high degree of sequence identity throughout their length. Potential recognition sequences for transcription factors that are present in the 5'-flanking region and are conserved between both genes include IFN-responsive elements, binding sites for AP-1, AP-2 and AP-3, and NF-IL 6 site, and a TATA-like sequence. Both genes map to chromosomal locations adjacent to genes encoding other cytokines, including IL-3, GM-CSF, IL-5, and IL-4, suggesting that IL-13 is another member of this cytokine gene family that may have arisen by gene duplication.

Amino Acid Sequence↗
PubMed1993

Interleukin 13 induces interleukin 4-independent IgG4 and IgE synthesis and CD23 expression by human B cells.

Recently the cDNA encoding interleukin 13 (IL-13), a T-cell-derived cytokine, was cloned and expressed. The present study demonstrates that IL-13 induces IgG4 and IgE synthesis by human B cells. IL-13-induced IgG4 and IgE synthesis by unfractionated peripheral blood mononuclear cells and highly purified B cells cultured in the presence of activated CD4+ T cells or their membranes. IL-13-induced IgG4 and IgE synthesis is IL-4-independent, since it was not affected by neutralizing anti-IL-4 monoclonal antibody. Highly purified, surface IgD+ B cells could also be induced to produce IgG4 and IgE by IL-13, indicating that the production of these isotypes reflected IgG4 and IgE switching and not a selective outgrowth of committed B cells. IL-4 and IL-13 added together at optimal concentrations had no additive or synergistic effect, suggesting that common signaling pathways may be involved. This notion is supported by the observation that IL-13, like IL-4, induced CD23 expression on B cells and enhanced CD72, surface IgM, and class II major histocompatibility complex antigen expression. In addition, like IL-4, IL-13 induced germ-line IgE heavy-chain gene transcription in highly purified B cells. Collectively, our data indicate that IL-13 is another T-cell-derived cytokine that, in addition to IL-4, efficiently directs naive human B cells to switch to IgG4 and IgE production.

Antibodies, Monoclonal↗