Biomedical subjects

C R Engwerda

Publications and source records attributed to C R Engwerda.

18 recordsLinked to original sources

PubMed2000

B cell-deficient mice are highly resistant to Leishmania donovani infection, but develop neutrophil-mediated tissue pathology.

Resolution of Leishmania infection is T cell-dependent, and B lymphocytes have been considered to play a minimal role in host defense. In this study, the contribution of B lymphocytes to the response against Leishmania donovani was investigated using genetically modified IgM transmembrane domain (muMT) mutant mice, which lack mature B lymphocytes. When compared with wild-type mice, muMT mice cleared parasites more rapidly from the liver, and infection failed to establish in the spleen. The rapid clearance of parasites in muMT mice was associated with accelerated and more extensive hepatic granuloma formation compared with wild-type mice. However, the liver of infected muMT mice also showed signs of destructive pathology, associated with the presence of increased numbers of neutrophils. The role of neutrophils in controlling parasite growth in the viscera was determined by depletion with the mAb RB6-8C5. This treatment led to a dramatic enhancement of parasite growth in both the liver and spleen of muMT and wild-type mice. As assessed by transfer of both normal and chronic-infection serum, Ig protects microMT mice from destructive hepatic pathology, but minimally alters their resistance compared with wild-type mice. However, adoptive transfer of CD4+ and CD8+ T cells into recombinase activating gene 1 (RAG1-/-) recipients, suggested that T cell function was not altered by maturation in a B cell-deficient environment. Taken together, these data suggest an inhibitory role for B lymphocytes in resistance to L. donovani unrelated to the presence or absence of Ig. However, Ig protects muMT mice from the exaggerated pathology that occurs during infection.

Adoptive Transfer↗

PubMed2000

Leishmania donovani infection of bone marrow stromal macrophages selectively enhances myelopoiesis, by a mechanism involving GM-CSF and TNF-alpha.

Alterations in hematopoiesis are common in experimental infectious disease. However, few studies have addressed the mechanisms underlying changes in hematopoietic function or assessed the direct impact of infectious agents on the cells that regulate these processes. In experimental visceral leishmaniasis, caused by infection with the protozoan parasite Leishmania donovani, parasites persist in the spleen and bone marrow, and their expansion in these sites is associated with increases in local hematopoietic activity. The results of this study show that L donovani targets bone marrow stromal macrophages in vivo and can infect and multiply in stromal cell lines of macrophage, but not other lineages in vitro. Infection of stromal macrophages increases their capacity to support myelopoiesis in vitro, an effect mediated mainly through the induction of granulocyte macrophage-colony stimulating factor and tumor necrosis factor-alpha. These data are the first to directly demonstrate that intracellular parasitism of a stromal cell population may modify its capacity to regulate hematopoiesis during infectious disease. (Blood. 2000;95:1642-1651)

Animals↗

PubMed2000

Organ-specific immune responses associated with infectious disease.

The immune response to infection can vary markedly in different organs of the same animal. In some organs, the infection can resolve with subsequent immunity to re-infection, whereas in other organs, pathogens can persist. Here, Christian Engwerda and Paul Kaye highlight the importance of defining organ-specific immune mechanisms for developing strategies that deal effectively with infectious diseases and their associated pathologies.

Animals↗

PubMed2000

Enhanced hematopoietic activity accompanies parasite expansion in the spleen and bone marrow of mice infected with Leishmania donovani.

In this study, we have analyzed hematopoietic activity in the spleen, bone marrow, and blood of BALB/c and scid mice infected with Leishmania donovani. Our analysis demonstrates that infection induces a rapid but transient mobilization of progenitor cells into the circulation, associated with elevated levels of granulocyte/macrophage colony-stimulating factor (GM-CSF) and MIP-1alpha. From 14 to 28 days postinfection, when parasite expansion begins in the spleen and bone marrow, both the frequency and cell cycle activity of hematopoietic progenitors, particulary CFU-granulocyte, monocyte, are dramatically increased in these organs. This is associated with increased accumulation of mRNA for GM-CSF, M-CSF, and G-CSF, but not interleukin-3. Our data also illustrate that hematopoietic activity, as assessed by changes in the frequency of progenitor cell populations and their levels of cell cycle activity, can be regulated in both a T-cell-independent and T-cell-dependent, as well as in an organ-specific, manner. Collectively, these data add to our knowledge of the long-term changes which occur in organs in which L. donovani is able to persist.

Animals↗

PubMed1999

Bromelain, from pineapple stems, proteolytically blocks activation of extracellular regulated kinase-2 in T cells.

Recently, it has emerged that extracellular proteases have specific regulatory roles in modulating immune responses. Proteases may act as signaling molecules to activate the Raf-1/extracellular regulated kinase (ERK)-2 pathway to participate in mitogenesis, apoptosis, and cytokine production. Most reports on the role of protease-mediated cell signaling, however, focus on their stimulatory effects. In this study, we show for the first time that extracellular proteases may also block signal transduction. We show that bromelain, a mixture of cysteine proteases from pineapple stems, blocks activation of ERK-2 in Th0 cells stimulated via the TCR with anti-CD3epsilon mAb, or stimulated with combined PMA and calcium ionophore. The inhibitory activity of bromelain was dependent on its proteolytic activity, as ERK-2 inhibition was abrogated by E-64, a selective cysteine protease inhibitor. However, inhibitory effects were not caused by nonspecific proteolysis, as the protease trypsin had no effect on ERK activation. Bromelain also inhibited PMA-induced IL-2, IFN-gamma, and IL-4 mRNA accumulation, but had no effect on TCR-induced cytokine mRNA production. This data suggests a critical requirement for ERK-2 in PMA-induced cytokine production, but not TCR-induced cytokine production. Bromelain did not act on ERK-2 directly, as it also inhibited p21ras activation, an effector molecule upstream from ERK-2 in the Raf-1/MEK/ERK-2 kinase signaling cascade. The results indicate that bromelain is a novel inhibitor of T cell signal transduction and suggests a novel role for extracellular proteases as inhibitors of intracellular signal transduction pathways.

Animals↗

PubMed1999

Leishmania donovani infection initiates T cell-independent chemokine responses, which are subsequently amplified in a T cell-dependent manner.

Control of Leishmania donovani infection in immunocompetent mice is associated with hepatic inflammation and granuloma formation, both of which are absent in severe combined immunodeficient (scid) mice. In both BALB/c and scid mice, L. donovani infection induced a rapid hepatic accumulation of mRNA encoding macrophage inflammatory protein-1alpha (MIP-(1alpha), monocyte chemoattractant protein-1 (MCP-1) and interferon-gamma inducible protein-10 (gammaIP-10). This response was not preceded by increased IL-4 production in either strain, unlike that reported in other infectious disease models. Interestingly, only gammaIP-10 mRNA was maintained at elevated levels throughout the first 7 days of infection, by mechanisms involving CD4+ and CD8+ T cells, and CD4+CD8+ cells not activated in scid mice. By in vivo depletion and reconstitution of scid mice it was demonstrated that T cells regulate the expression of all three chemokines studied, while they themselves only produce gammaIP-10 in appreciable quantities.

Animals↗

PubMed1998

Blockade of CTLA-4 enhances host resistance to the intracellular pathogen, Leishmania donovani.

CTLA-4 has recently been shown to act as a negative regulator of T cell activation. Here we provide evidence that blockade of CTLA-4 can result in enhanced host resistance to an intracellular pathogen. The administration of anti-CTLA-4 mAb 4F10 to BALB/c mice, 1 day following infection with Leishmania donovani, enhanced the frequency of IFN-gamma and IL-4 producing cells in both spleen and liver, and dramatically accelerated the development of a hepatic granulomatous response. The expression of mRNA for the CXC chemokine gammaIP-10 was also elevated above that seen in control Ab treated mice, and was directly correlated with the frequency of IFN-gamma producing cells. In contrast, macrophage inflammatory protein-1alpha (MIP-1alpha) and monocyte chemotactic protein-1 (MCP-1) mRNA levels were unaffected by anti-CTLA-4 treatment, suggesting that CTLA-4 blockade may exert selective effects on chemokine expression. These changes in tissue response and cytokine/chemokine production were accompanied by a 50 to 75% reduction of parasite load in the spleen and liver of anti-CTLA-4-treated animals compared to controls. Furthermore, administration of anti-CTLA-4 mAb 15 days after L. donovani infection, when parasite burden is increasing in both organs, also resulted in enhanced resistance. Thus, these studies indicate a potent immunomodulatory and potentially therapeutic role for interventions targeted at CTLA-4.

Abatacept↗

PubMed1998

Neutralization of IL-12 demonstrates the existence of discrete organ-specific phases in the control of Leishmania donovani.

IL-12 plays a key role in stimulating both innate and antigen-specific immune responses against a number of intracellular pathogens. A neutralizing anti-IL-12 monoclonal antibody (mAb) was used to define and compare the role of endogenous IL-12 in the liver and spleen of mice infected with Leishmania donovani. IL-12 neutralization both early and late in infection caused delayed resolution of parasite load, a transient decrease in IFN-gamma, IL-4, TNF-alpha and inducible nitric oxide synthase (NOS-2) production, and suppressed tissue granuloma formation in the liver of genetically susceptible BALB/c mice. In contrast to the liver of BALB/c mice, neutralization of IL-12 had no effect on parasite burden in the spleen over the first 28 days of infection. However, IL-12 appeared to be critical for the development of mechanisms which subsequently contain the growth of persistent parasites in this organ in that neutralization of IL-12 dramatically enhanced parasite growth after day 28 of infection. Following IL-12 neutralization, the later unchecked growth of parasites in the spleen was coincident with an extensive breakdown of the tissue microarchitecture. Immunohistochemical studies revealed that IL-12 was largely produced by uninfected cells in L. donovani-infected BALB/c mice. In contrast, the course of infection in the liver and spleen of genetically resistant CBA/n mice was unaffected by the administration of anti-IL-12 mAb. These results suggest that the liver and spleen in susceptible BALB/c mice have different temporal requirements for IL-12 in controlling L. donovani infection, whereas IL-12 plays little role in either organ in resistant CBA/n mice. In addition, IL-12 appears to be involved in the generation of both Th1 and Th2 responses during L. donovani infection in BALB/c mice.

Animals↗

PubMed1998

Dendritic cells, but not macrophages, produce IL-12 immediately following Leishmania donovani infection.

Infection with Leishmania, an obligate intracellular parasite of mononuclear phagocytes, stimulates the production of IFN-gamma from NK cells, via a pathway which is dependent upon IL-12 and IL-2. IL-12 is also essential for the development of host protective T cell responses to this parasite. However, previous in vitro studies have indicated that macrophages fail to make IL-12 following infection with Leishmania, and that subsequent to infection, macrophages become refractory to normal IL-12-inducing stimuli. We have used an in situ approach to attempt to resolve this apparent paradox, and by immunostaining for IL-12 p40 protein, we now demonstrate for the first time, that dendritic cells (DC) are the critical source of early IL-12 production following Leishmania infection. IL-12 production by DC is transient, peaking at 1 day post infection and returning to the levels seen in uninfected mice by day 3. Although resident tissue macrophages fail to produce IL-12 after Leishmania infection, these cells are not totally refractory to cytokine inducing stimuli, as TNF-alpha production is induced by day 3 post infection. Not only do these data satisfactorily explain the differences between in vivo and in vitro data by identifying the cellular source of IL-12, but they also suggest a novel model for NK cell activation; namely that in response to pathogens which fail to trigger IL-12 production by macrophages, DC-T cell clusters provide the microenvironment for initial NK cell activation.

Animals↗

PubMed1997

B7-2 blockade enhances T cell responses to Leishmania donovani.

Infection with Leishmania donovani has been reported to induce a dominant Th1-type response in all strains of mice examined, providing a model for examining the regulation of Th1 responses in the relative absence of Th2 cross-regulation. Here we demonstrate that blockade of the costimulatory molecule B7-2, but not B7-1, has significant effects on disease progression, measured as day 28 parasite burden in the liver. The effects of B7-2 blockade were associated with increased IFN-gamma production, as determined 1) following restimulation with specific Ag, 2) by enumeration of IFN-gamma-secreting cells using ELISPOT assays, and 3) by analysis of IFN-gamma mRNA by reverse transcription-PCR. Surprisingly, IL-4-producing cells were also readily detected in infected mice by ELISPOT analysis. The frequency of these IL-4-producing cells and of IL-4 mRNA levels was also enhanced in the liver of infected mice treated with anti-B7-2 mAb. Administration of anti-B7-2 from the day of infection or delaying its administration until day 3 after infection had similar effects. Parasite-specific IgG1 and IgG2a responses were either unaffected or marginally increased following anti-B7-2 administration, contrary to the inhibitory effect of this treatment on responses to the T-dependent Ag DNP-BSA. These data support a model of T cell activation whereby B7-2/CD28 interactions play a relatively redundant role in initial T cell activation, but in which interference with later B7-2/CTLA4 interaction potentiates established cytokine responses.

Animals↗

PubMed1997

Destruction of follicular dendritic cells during chronic visceral leishmaniasis.

Follicular dendritic cells (FDCs) play a pivotal role in the germinal center (GC) response and in the development and regulation of B lymphocytes. Pathologic changes in GCs and a loss of FDCs have previously been noted in various viral infections, notably HIV-1. However, such changes have not been formally described in a chronic parasitic infection. In BALB/c mice infected with Leishmania donovani, parasites persist in the spleen for long periods, with associated splenomegaly. To examine the fate of FDC during the course of this chronic infection, we used 1) immunohistology, with FDC-specific mAbs; and 2) passive immunization with immune complexes, followed by light and electron microscopy. This study demonstrates that destruction of FDCs and a concomitant loss of GCs are associated with chronic visceral leishmaniasis. These pathologic effects are notable from 4 wk postinfection. At 8 wk postinfection and beyond, FDC are almost undetectable by both immunohistology and functional immune complex trapping. The loss of FDCs is associated with the infiltration of heavily parasitized macrophages into the GC, and reduction in parasite burden by chemotherapy is able to retard the process of FDC destruction. These data directly demonstrate for the first time the loss of FDCs during a chronic parasite infection and suggest a mechanism underlying the aberrant regulation of B cell function in murine visceral leishmaniasis.

Animals↗

PubMed1996

An age-related decrease in rescue from T cell death following costimulation mediated by CD28.

We previously reported that T cell proliferation in response to a primary signal through the T cell receptor (TCR) and a costimulatory signal via the CD28 molecule is impaired in healthy, aged mice. Here we extend these studies to examine factors which may be involved in this defect in T cells from aged mice. To determine if age-related changes in cytokine production might be responsible, splenic T cells from young (2-4 months) and aged (20-26 months) mice were stimulated with immobilized anti-CD3 epsilon and soluble anti-CD28 mAbs in the presence of exogenous IL-2, IL-4, IFN-gamma, IL-1 alpha, or IL-6. No improvement in the proliferative response of T cells from aged mice was found following the addition of any cytokine. In addition, the decreased proliferative response of T cells from aged mice was not caused by the enhanced production of IFN-gamma or other inhibitory factors. Interestingly, despite the age-related reduction in proliferation, no significant difference was found in the percentage of live cells entering the S, G2, or AM phase of the cell cycle in stimulated T cells from young and aged mice. Instead, anti-CD28-mediated costimulation was found to rescue T cells from young mice from anti-CD3epsilon-induced cell death, but did not rescue T cells from aged mice. This failure of T cells from aged mice to respond to costimulatory signals appears to contribute to the decreased proliferation observed from cultures containing these cells, and may be involved in many other age-related alterations in immunological responsiveness.

Aging↗

PubMed1996

Cytokine production by T lymphocytes from young and aged mice.

We previously have shown that T cell proliferation in response to a primary signal through the CD3 epsilon chain and a costimulatory signal via the CD28 molecule is impaired in healthy, aged mice. To determine whether age-related alterations in cytokine production might explain the reduced proliferative responses of T cells from aged mice, we examined the secretion of the major T cell immunoregulatory cytokines, IFN-gamma, IL-4, and IL-2. Splenic T cells from young (2 to 4 mo) and aged (20 to 26 mo) mice were studied. T cells were stimulated with immobilized anti-CD3 epsilon chain mAb and soluble anti-CD28 mAb for 24 h. T cells from aged mice, when compared with young controls, showed increased IFN-gamma production, no difference in IL-4 production, and decreased IL-2 production. Most IFN-gamma was produced by CD8+ T cells, whereas most IL-2 and IL-4 was produced by CD4+ T cells. Both CD4+ and CD8+ T cells from aged mice produced significantly more IFN-gamma than corresponding cells from young mice. This increased production could be accounted for by increased numbers of CD4+CD44high and CD8+CD44high T cells in aged animals. CD4+CD44high and CD8+CD44high T cells from young mice produced comparable amounts of IFN-gamma as corresponding cells from aged mice. In contrast to unseparated splenic T cells, no age-related difference in IL-2 or IL-4 production by purified CD4+ T cells was observed. Similarly, when CD4+ T cells were further separated into CD44low and CD44high subpopulations, no age-related difference in IL-2 production was found. Therefore, we found no consistent evidence that diminished production of the major T cell growth factors, IL-2 and IL-4, is responsible for the age-related decrease in the proliferation of T cell subpopulations that were stimulated in vitro through the CD3 epsilon chain and costimulated via the CD28 molecule. The physiologic relevance of increased IFN-gamma production by T cells from aged mice is unknown.

Aging↗

PubMed1996

An in vivo analysis of cytokine production during Leishmania donovani infection in scid mice.

Leishmania donovani, the causative agent of visceral leishmaniasis, fails to induce NK cell activation in scid mice. In order to further our understanding of the host response to L. donovani, we analysed cytokine mRNA accumulation and TNF alpha protein synthesis in the liver of scid and BALB/c mice infected with this parasite. scid mice infected with L. donovani exhibited very little proinflammatory response, as measured by cytokine mRNA accumulation and TNF alpha protein expression, supporting the notion of a relatively "quiet" interaction between L. donovani and macrophages in these animals. In contrast, immunocompetent BALB/c mice were found to generate an early IFN gamma response, coincident with a rise in IL-2 mRNA levels and elaboration of a tissue response involving TNF alpha production by infected Kupffer cells. These results extend our understanding of the response of BALB/c and scid mice to L. donovani infection and highlight the value of cytokine analysis at both the tissue and cellular levels.

Animals↗

PubMed1996

IgE, TNF alpha, IL1 beta, IL4 and IFN gamma gene polymorphisms in sheep selected for resistance to fleece rot and flystrike.

Investigation of restriction fragment length polymorphisms (RFLPs) associated with immunoglobulin E (IgE) and cytokine genes in the sheep genome revealed polymorphisms in the IgE constant heavy chain, interferon gamma and interleukin 4 genes. No polymorphisms were found in interleukin 1 beta or tumour necrosis factor alpha. PstI and BamHI RFLPs in the IgE gene showed differences in frequency between animals selected for resistance or susceptibility to fleece rot and blowfly strike.

Animals↗

PubMed1994

Aged T cells are hyporesponsive to costimulation mediated by CD28.

The ability of T cells to proliferate in response to a number of stimuli is impaired in healthy, aged individuals. T cells from young (2 to 4 mo) and aged (20 to 26 mo) mice were stimulated with immobilized anti-CD3 epsilon-chain mAb and soluble anti-CD28 mAb. T cells from young and aged mice proliferated comparably in response to anti-CD3 epsilon mAb alone. However, aged T cells were significantly less responsive to costimulation by anti-CD28 mAb. This decreased response of aged T cells was seen at all dosages tested of anti-CD3 epsilon and anti-CD28 mAbs and in the presence and absence of APC. Similar results were observed when costimulation was provided by B7-transfected L cell fibroblasts. T cells from young and aged mice had comparable expression of CD28 by flow cytometry, both before and after stimulation. The defect in response to CD28 was seen both in CD4+ and CD8+ T cells and in CD44lo (naive) and CD44hi (memory) T cells. The impaired response to costimulation mediated by CD28 on T cells from aged mice may be an important factor in reduced T cell responses associated with aging.

Aging↗

PubMed1992

Isolation and sequence of sheep immunoglobulin E heavy-chain complementary DNA.

A complementary DNA (cDNA) corresponding to sheep immunoglobulin E heavy (IgE H) chain messenger RNA (mRNA) was isolated and sequenced. A fragment of sheep IgE constant H (epsilon)-chain was initially synthesized using the polymerase chain reaction (PCR) and single-stranded cDNA prepared from the mRNA of parasite-stimulated sheep lymph nodes. This fragment was then used to probe a cDNA library, again prepared from a parasite-stimulated lymph node. A recombinant clone containing cDNA encoding a sheep IgE H-chain of 1802 base pairs was isolated and the H-chain cDNA-sequenced. The nucleotide sequence was found to code for a complete sheep IgE H-chain, consisting of both variable (V) and constant (C) regions. When the amino acid sequence derived from the nucleotide sequence was compared to other species epsilon-chains, interesting homologies and differences between corresponding domains were found, including conservation in cysteine and tryptophan residues and variable glycosylation sites.

Amino Acid Sequence↗

PubMed1992

The isolation and sequence of sheep interleukin 4.

A cDNA corresponding to sheep IL-4 has been isolated and sequenced. The cDNA was synthesized using PCR and oligonucleotides designed from conserved regions of IL-4 cDNA published sequences. The nucleotide and amino acid sequences of a sheep IL-4 cDNA are presented and compared with sequences from other species. At the nucleic acid level, the sheep cDNA shared 73 and 62% homology with human and mouse cDNA homologues, respectively, while comparisons at the amino acid level revealed 50% homology with human IL-4 and 33% with the mouse homologue. Total amino acid homology between these species was 27%.

Amino Acid Sequence↗