Biomedical subjects

G Kraal

Publications and source records attributed to G Kraal.

At least 19 recordsLinked to original sources

PubMed2005

New cohorts of naive T cells exacerbate ongoing allergy but can be suppressed by regulatory T cells.

Although as pretreatment oral tolerance is a potent means to achieve systemic suppression, its application in ongoing disease is controversial. Here we propose that availability of naive T cells may critically determine whether immunological tolerance is achieved during ongoing antigenic reactivity. Infusion of naive antigen-specific T cells into mice directly prior to eliciting a secondary Th2 response induces these naive cells to actively engage in the antigenic response despite presence of established memory. Naive antigen-specific T-cells divided faster, produced more interleukin (IL)-2, IL-4 and IL-5 and enhanced immunoglobulin E (IgE) release during a secondary Th2 response, compared with naive T cells that were infused prior to a primary response. Despite such contribution by new cohorts of naive T cells co-infusion of mucosal Tr together with naive T cells could suppress enhanced IgE release during a secondary Th2 response. We conclude that naive T cells contribute to a secondary Th2 response and although they can still be suppressed in the presence of sufficient numbers of mucosal Tr, they may interfere with potential therapeutic application of mucosal tolerance.

Animals↗

PubMed2005

A NFKB1 promoter polymorphism is involved in susceptibility to ulcerative colitis.

Nuclear factor kappaB (NF-kappaB) designates a group of critical transcription factors involved in a variety of immunologic and/or inflammatory processes. Conceivably, genes involved in the NF-kappaB pathway make interesting candidate genes for chronic inflammatory disorders, including the inflammatory bowel diseases (IBD), Crohn's disease (CD) and ulcerative colitis (UC). In two mouse models of colitis, strong linkage has been observed with a locus on chromosome 3 that harbours the Nfkb1 gene. In addition, a polymorphism in the promoter region of the human NFKB1 gene was found to be associated with susceptibility to UC. In this study, we searched to confirm this previously found association in IBD in a different population. Allele and genotype frequencies of the -94 ins/delATTG polymorphism were determined in 266 unrelated Dutch Caucasian IBD patients (127 UC, 139 CD), and 155 matched healthy controls. The allele frequency of the deletion was significantly higher in UC patients (P = 0.019), but not in CD patients, compared to healthy controls, and the UC patients homozygous for the -94 ATTG deletion had a younger age of onset. Our findings confirm the previously found association between this polymorphism and susceptibility to UC in an independent study population and adds further evidence for the role of this gene in disease susceptibility.

Adult↗

PubMed2004

Preferential expression of IgG2b in nose draining cervical lymph nodes and its putative role in mucosal tolerance induction.

Induction of intranasal tolerance prevents the body from eliciting unwanted immune responses against harmless antigens that enter the body through the nasal mucosa. To study the intrinsic capacities of the cervical, nose draining lymph nodes (CLN), which are essential for tolerance induction, genes that are differentially expressed in CLN and not in peripheral lymph nodes (PLN) were characterized. The gene that is predominantly overexpressed in CLN codes for IgG2b. This is confirmed by a higher percentage of IgG2b+ B220+ cells in CLN compared with any PLN. However, this predominance of IgG2b-positive B cells in the CLN is not specific for the lymph node itself but rather determined by the region drained by lymph nodes at the cervical site, as transplanted PLN at these locations show a comparable predominance. It was demonstrated that IgG2b, when compared with IgG1, led to differential activation of dendritic cells (DC) through Fc receptor signalling. The results point to a unique local combination of cells and factors in the nose draining CLN leading to highly specialized immune reactivity. The results point out that predominance of a distinct IgG isotype in a lymphoid environment may lead to highly specialized immune reactivity.

Animals↗

PubMed2002

[Inducing tolerance against antigens through initial contact via the mucous membrane].

Mucosal tolerance arises in response to protein antigens that enter through the mucous membranes. This tolerance is unusual in that it becomes systemic and also arises when these antigens subsequently enter the body through the skin or via the bloodstream. Clinical applications of mucosal tolerance are hampered because induction of tolerance does not appear to be possible once systemic sensitisation has taken place. Research into the immunological mechanisms which underlie tolerance induction indicates marked local differences in antigen presentation and the formation of special classes of T lymphocytes which regulate immune reactions. In the future, this knowledge could lead to the application of tolerance in the selective therapeutic down-regulation of immunological diseases such as allergies and autoimmune diseases.

Antigen Presentation↗

PubMed2001

Alveolar macrophages, surfactant lipids, and surfactant protein B regulate the induction of immune responses via the airways.

The influences of alveolar macrophages (AM) and pulmonary surfactant on the induction of immune responses via the airways were assessed. Mice were depleted of their AM by intratracheal instillation of multilamellar vesicles containing dichloromethylene-diphosphonate followed by intratracheal instillation of a T cell--dependent antigen, trinitrophenyl--keyhole limpet hemocyanin, in vesicles of various compositions. The primary immune response was determined in the spleen of these animals using an ELI-Spot assay. The secondary immune responses in the sera of the mice were assessed using enzyme-linked immunosorbent assays. An immune response was detected in animals depleted of their AM and intratracheally instilled with antigen in small unilamellar vesicles consisting of either phosphatidylcholine cholesterol or surfactant lipids. Incorporation of surfactant protein (SP)-B in the antigen vesicles enhanced the immune response, whereas SP-A or SP-C in the antigen vesicle did not have an effect. Strikingly, intratracheal instillation of SP-B containing antigen vesicles can induce an immunoglobulin M immune response in mice without depletion of AM. These results indicate that SP-B containing vesicles can enhance the induction of immune responses via the airways and further illustrate the important roles of both AM and pulmonary surfactant in the pulmonary immune system.

Animals↗

PubMed2001

Regulation of immunological mucosal tolerance.

Mucosal tolerance is an immunological phenomenon specific to mucosal surfaces as found in the lungs and gastrointestinal tract. It results in the suppression of immune responses to inhaled or ingested antigens and prevents the body from unwanted and unnecessary immunological responses to harmless molecules, such as grass-pollen or food constituents. This imposes the difficult task for the immune system of keeping a balance between reacting and non-reacting, and disturbances of this balance result in allergies and, possibly, autoimmunity, as well as opportunistic infections and even an escape from tumor surveillance. Understanding the mechanisms that underlie mucosal tolerance is, therefore, important from different viewpoints. Maintenance or (re)induction of mucosal tolerance to, e.g., food proteins, airborne allergens or autoantigens is desirable to prevent or cure allergies and autoimmune diseases. However, induction of mucosal tolerance is an unwanted phenomenon in mucosal vaccination and in the case of mucosal tumors.

Animals↗

PubMed2000

T cell reactivity to heat shock protein 60 in diabetes-susceptible and genetically protected nonobese diabetic mice is associated with a protective cytokine profile.

Spontaneous onset of pancreatic beta cell destruction in the nonobese diabetic (NOD) mouse is preceded by the induction of autoreactive T cells, which recognize a variety of autoantigens. The 60-kDa endogenous (murine) heat shock protein 60 (hsp60) has been proposed to be one of the key autoantigens. Here we demonstrate that subcutaneous immunization of normoglycemic NOD mice with highly homologous mycobacterial or murine hsp60 activates T cells in the spleen that produce high levels of IL-10 upon restimulation in vitro with either hsp60 protein. In time, increasing levels of hsp60-induced IL-10 could be detected in NOD mice, but not in age- and MHC class II-matched BiozziABH mice, which lack any sign of pancreatic inflammation. These results suggest that the IL-10 responses in NOD mice are primarily driven by endogenous inflammation. Genetically protected NOD-asp mice, showing a less progressive development of insulitis, demonstrated a similar increase in hsp60-induced IL-10 in time compared with wild-type NOD mice. Taken together, our results suggest that endogenous hsp60 is not a primary autoantigen in diabetes but is possibly associated with regulation of insulitis. Moreover, the capacity to respond to (self) hsp60 is independent of the MHC class II-associated genetic predisposition to diabetes.

Animals↗

PubMed2000

Isolation of the intact white pulp. Quantitative and qualitative analysis of the cellular composition of the splenic compartments.

The spleen is anatomically and functionally divided into two compartments: the red pulp, where particles are effectively removed from the blood, and the white pulp, where specific immune responses are generated. Here the isolation of white pulp from red pulp is described, allowing a detailed analysis of the cellular components of both red and white pulp separately. A striking abundance of memory T cells was found in the white and red pulp with an overall ratio of T and B cells in the white pulp being similar to that in lymph nodes. Both NK and gamma delta T cells can be found in white pulp and lymph nodes, but granulocytes are absent. The distribution of dendritic cell subsets showed significant differences between white pulp and lymph nodes. Furthermore, short-term homing experiments showed that migration of lymphocytes into the white pulp greatly exceeded that into lymph nodes, with significant differences in migration of various lymphocytes subsets. This suggests a different migration and retention mechanism in the white pulp. This new isolation technique will allow further analysis of the functional capacities of the splenic compartments.

Animals↗

PubMed2000

The macrophage receptor MARCO.

MARCO (macrophage receptor with collagenous structure) belongs to the class A scavenger receptor molecules. The structure and function of the molecule is described. Although it is expressed on subsets of macrophages, it can be upregulated on other macrophages after bacterial infection. The strategic position of MARCO-expressing cells in lymphoid organs suggests an important role for this bacteria-binding molecule in removal of pathogens.

Animals↗

PubMed1999

Intranasally induced immunological tolerance is determined by characteristics of the draining lymph nodes: studies with OVA and human cartilage gp-39.

Mucosal tolerance is a naturally occurring immunological phenomenon that prevents harmful inflammatory responses to ingested or inhaled environmental, predominantly nondangerous, Ags. The nasal mucosa is an extremely efficient compartment in the induction of immunological tolerance which can be exploited in Ag-specific treatment of autoimmune disease. With the use of a model Ag (OVA) and an Ag implicated in the autoimmune disease rheumatoid arthritis (human cartilage gp-39), we here show in a mouse model that the superficial cervical and internal jugular lymph nodes that drain the nasal mucosa are instrumental in the induction of tolerance. Removal of these lymph nodes abrogates tolerance induction, which can be restored by transplantation of superficial cervical lymph nodes, but not of peripheral lymph nodes. The results indicate that lymph nodes that directly drain the nasal mucosa constitute a unique microenvironment which favors the induction of immunological tolerance.

Adipokines↗

PubMed1999

Regulation and functional involvement of macrophage scavenger receptor MARCO in clearance of bacteria in vivo.

The scavenger receptors expressed by macrophages are thought to play an important role in the immune response against bacteria by mediating binding and phagocytosis. A novel member of the class A scavenger receptor family, macrophage receptor with collagenous structure (MARCO), has recently been identified. In this study we have generated a panel of mAbs with specificities for different domains of this receptor. Two of those reacting with the C-terminal cysteine-rich domain block ligand binding of MARCO. The in vivo expression of this murine receptor is normally restricted to distinct populations of macrophages in the spleen and lymph nodes. During bacillus Calmette-Guérin (BCG) infection, during bacterial sepsis, or after the injection of purified LPS, however, the expression of MARCO is rapidly induced on macrophages in other tissues, including Kupffer cells in the liver. Using the mouse macrophage cell line J774.2, it was shown that LPS stimulation up-regulates surface expression of MARCO in a dose- and time-dependent fashion. The proinflammatory cytokines IL-1, IL-6, TNF-alpha, and IFN-gamma had little or no effect. Using inhibitory mAbs, the relevance of MARCO for the clearance of circulating bacteria in vivo was determined. Although the overall elimination of live Escherichia coli and Staphylococcus aureus from the blood did not appear to be affected by treatment with these Abs, the capturing of heat-killed bacteria by macrophages in the marginal zone areas of the spleen was clearly inhibited. This study suggests a role for MARCO in the host antibacterial defense.

Animals↗

PubMed1999

Role of macrophage scavenger receptors in hepatic granuloma formation in mice.

In mice homozygous for the gene mutation for type I and type II macrophage scavenger receptors (MSR-A), MSR-A-/-, the formation of hepatic granulomas caused by a single intravenous injection of heat-killed Corynebacterium parvum was delayed significantly for 10 days after injection, compared with granuloma formation in wild-type (MSR-A+/+) mice. In the early stage of granuloma formation, numbers of macrophages and their precursor cells were significantly reduced in MSR-A-/- mice compared with MSR-A+/+ mice. In contrast to MSR-A+/+ mice, no expression of monocyte chemoattractant protein-1, tumor necrosis factor-alpha, and interferon-gamma mRNA was observed in MSR-A-/- mice by 3 days after injection. Also in MSR-A-/- mice, uptake of C. parvum by Kupffer cells and monocyte-derived macrophages in the early stage of granuloma formation was lower and elimination of C. parvum from the liver was slower than in MSR-A+/+ mice. In the livers of MSR-A+/+ mice, macrophages and sinusoidal endothelial cells possessed MSR-A, but this was not seen in the livers of MSR-A-/- mice. In both MSR-A-/- and MSR-A+/+ mice, expression of other scavenger receptors was demonstrated. These data suggest that MSR-A deficiency impairs the uptake and elimination of C. parvum by macrophages and delays hepatic granuloma formation, particularly in the early stage.

Animals↗

PubMed1999

Progression and regression of atherosclerosis in APOE3-Leiden transgenic mice: an immunohistochemical study.

Apolipoprotein E3-Leiden (APOE3-Leiden) transgenic mice develop hyperlipidemia and are highly susceptible to diet-induced atherosclerosis. We have studied the progression and regression of atherosclerosis using immunohistochemistry. Female transgenic mice were fed a moderate fat diet to study atherosclerosis over a longer time period. Fatty streaks arose in the intima and consisted of lipid filled macrophages which differed in origin. All macrophages expressed the macrophage scavenger receptor while two thirds expressed sialoadhesin and were positive for an antibody recognizing marginal zone macrophages (MOMA-1). All macrophages were negative for the scavenger receptor MARCO and 50% were positive for CD4. Small fatty streaks contained CD-3 positive T-lymphocytes which were for more than 70% CD4-positive. ICAM-1 was positive both in atherosclerotic and control mice. In early plaques, fibrosis was observed on the luminal and medial site of the foam cells while smooth muscle cells were only observed in the fibrous cap. To study regression, we used a high fat, high cholesterol diet to rapidly induce atherosclerosis (14 weeks). The animals were then fed normal chow. Subsequently, atherosclerosis was assayed over time (4, 8, 16 weeks). Cholesterol levels dropped in 4 weeks to control levels. The animals did not show a significantly decrease in plaque size over time. but the percentage macrophages was significantly smaller in the animals after 4 weeks. In conclusion, the APOE3-Leiden mouse is a useful model to study the progression and regression of atherosclerosis.

Animals↗

PubMed1999

Glucocorticoids modulate the development of dendritic cells from blood precursors.

Dendritic cells (DC) are professional antigen-presenting cells, capable of priming naive T cell responses. Glucocorticoids (GC) are frequently used in asthmatic patients. In this study we describe the effects of GC on the development and function of monocyte-derived DC (MoDC) in vitro and in vivo. Monocytes from healthy individuals were isolated and incubated with granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL-4 for 6 days, to induce maturation into MoDC. To study the role of GC on DC differentiation in vitro cells were incubated with dexamethasone at different stages of MoDC development. At day 6 cells were characterized phenotypically by flow cytometry and functionally in an allogeneic mixed leucocyte reaction. To study the effect of GC in vivo patients with mild/moderate atopic asthma were selected. In one group no GC were used, whereas the other group used inhalation GC. MoDC from these patients were generated as described above and tested functionally. Incubation of MoDC or its peripheral blood precursors with dexamethasone decreased the accessory potency dose-dependently. The functional differences could not be explained by the changes in the expression of MHC II and the costimulatory molecules CD40 and CD86. The relevance of this mechanism was confirmed for the in vivo situation as well. MoDC from patients using inhalation GC showed a decreased accessory potency. These data suggest a modulatory effect of GC therapy at the level of the peripheral blood monocyte. The results indicate that GC influence DC development and function in vitro as well as in vivo.

Administration, Inhalation↗

PubMed1998

The steroid hormone dehydroepiandrosterone (DHEA) breaks intranasally induced tolerance, when administered at time of systemic immunization.

The induction of intranasal tolerance might be dependent on specific characteristics of mucosal, nose-draining lymph nodes. Such a specific characteristic might lie in the metabolism of the steroid hormone DHEA. Conversion of the prohormone DHEAS into DHEA is dependent on DHEAS-sulphatase activity in lymph nodes. This activity is low in mucosa-draining lymph nodes compared to peripheral lymph nodes, leading to differences in microenvironment. However, administration of DHEA before the induction of intranasal tolerance, could not change tolerance induction. We next determined the effect of DHEA after the induction of intranasally induced tolerance and demonstrated that the steroid hormone and some of its derivatives are able to break tolerance, when administered at time of systemic immunization. These findings might have implications for the regulation of intranasal tolerance and the use of DHEA.

Administration, Intranasal↗

PubMed1998

Lymphocyte triggering via L-selectin leads to enhanced galectin-3-mediated binding to dendritic cells.

For proper immune surveillance, naive lymphocytes are recruited from the blood into secondary lymphoid organs. L-selectin expressed on lymphocytes plays an important role in the initial attachment of these cells to high endothelial venules (HEV) in lymph nodes. Previously, we found that triggering via L-selectin resulted in activation of lymphocytes, followed by an alteration in their adhesion capacity. This suggested that L-selectin triggering might play a role in cell-cell interactions after lymph node entry. Here, we identify a novel adhesion mechanism involving L-selectin-triggered lymphocytes and dendritic cells, and we show that enhanced binding to dendritic cells is mediated by galectin-3 and not by integrins. Furthermore, it was shown that L-selectin-triggered T lymphocytes exhibited enhanced proliferation in an allogeneic mixed lymphocyte reaction. It is concluded that, in addition to a role for L-selectin in tethering and rolling on endothelium, triggering of the molecule on the lymphocyte surface leads to changes that are pertinent for the function of the cell after passing the HEV. We argue that the described adhesion mechanism plays a role in optimizing the initial interaction between dendritic cells and lymphocytes.

Animals↗

PubMed1998

Regulation of fucosyltransferase-VII expression in peripheral lymph node high endothelial venules.

Binding of L-selectin to the highly glycosylated peripheral lymph node addressins (PNAd) plays a central role in the normal recirculation of lymphocytes between the bloodstream and the lymph node. This interaction requires correct fucosylation of the PNAd, mediated by the recently identified fucosyltransferase-VII (Fuc-TVII). Here we show that during ontogeny Fuc-TVII is absent at the day of birth, barely detectable on day 1, and clearly present from day 2 onwards. PNAd expression as detected by the MECA-79 antibody precedes the expression of Fuc-TVII. Furthermore, we demonstrate that in adult mice antigenic stimulation of peripheral lymph nodes leads to a temporary disappearance of Fuc-TVII at days 2 and 3 after stimulation, followed by a complete reappearance by day 4, while expression of MECA-79 is never completely absent during this period. Finally, occlusion of afferent lymphatics to peripheral lymph nodes resulted in a decreased expression of Fuc-TVII in the high endothelial venules by day 5, and complete disappearance within 8 days. We conclude that the activity of Fuc-TVII in cells of high endothelial venules is directly affected by afferent lymph and activation processes that occur in the lymph node after antigenic stimulation. The expression of Fuc-TVII is therefore yet another level at which the function of high endothelial venules, and thus lymphocyte trafficking, can be regulated.

Animals↗

PubMed1998

Functional immaturity of rat alveolar macrophages during postnatal development.

Alveolar macrophages (AM) are important in the regulation of immune responses in the lung, through their role as scavenger cells and through the production of many bioactive factors. Because in early infancy pulmonary infections are a recurrent problem, we studied the postnatal functional maturation of AM in a rat model. AM were isolated from rat lungs by bronchoalveolar lavage at several time intervals after birth and tested for their ability to ingest Escherichia coli in the presence of surfactant protein A (SP-A). Furthermore, their capacity to produce nitric oxide (NO) and interleukin-1 beta (IL-1 beta) after in vitro lipopolysaccharide (LPS) stimulation was analysed, as well as their capacity to downregulate proliferation of T cells from both mature and neonatal rats. SP-A-mediated phagocytosis of E. coli by AM was reduced in 14-day-old neonatal rats, as compared with mature rats (P < or = 0.05). Also the IL-1 beta production by rat AM after LPS stimulation was impaired at 14 days of age, as compared with IL-1 beta production by AM from mature rats (P < or = 0.05). In contrast, the LPS-induced NO production by rat AM as well as the capacity to inhibit T-cell proliferation were well developed at all ages tested. In conclusion, during postnatal development the rat AM is functionally immature, with respect to phagocytosis and secretion of inflammatory mediators. These differences may underly the enhanced susceptibility to pulmonary infections as found in human neonates.

Analysis of Variance↗