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Biomedical subjects

H Kiyono

Publications and source records attributed to H Kiyono.

At least 37 records · Page 2Linked to original sources
PubMed2001

Genetically manipulated bacterial toxin as a new generation mucosal adjuvant.

Cholera toxin (CT) and heat-labile toxin (LT) of Escherichia coli act as adjuvants for the enhancement of mucosal and serum antibody (Ab) responses to mucosally co-administered protein antigen (Ag). Both LT and CT induce B7-2 expression on antigen-presenting cells (APCs) for subsequent co-stimulatory signalling to CD4+ T cells. CT directly affects CD4+ T cells activated via the TCR-CD3 complex with selective inhibition of Th1 responses whereas LT maintains Th1 cytokine responses with inhibition of interleukin (IL)-4 production. Interestingly, while CT failed to induce mucosal adjuvant activity in the absence of IL-4, LT did so. Nontoxic mutant (m)CTs (S61F and E112K) retain adjuvant properties by inducing CD4+ Th2 cells, which provided effective help for the Ag-specific mucosal immunoglobulin (Ig)A, as well as serum IgG1, IgE and IgA Ab responses. The mCT E112K has been shown to exhibit two distinct mechanisms for its adjuvanticity. Firstly, mCT enhanced the B7-2 expression of APCs. Secondly, this nontoxic CT derivative directly affected CD4+ T cells and selectively inhibited Th1 cytokine responses. Thus, several lines of evidence indicate that enzyme activity can be separated from adjuvant properties of CT and this offers promise for the development of safe delivery of vaccines for mucosal IgA responses.

Adjuvants, Immunologic↗
PubMed2001

The mucosal immune system: from specialized immune defense to inflammation and allergy.

The mucosal immune system is a first line of defense against foreign antigens, including microbial and dietary antigens. Under normal circumstances, the mucosal immune system employs tightly regulated dynamic mucosal intra- and internets consisting of inductive and effector sites for the induction of an appropriate immunological homeostasis between the host and mucosal environments. The common mucosal immune system (CMIS), which interconnects between inductive (e.g. Peyer patch) and effector (e.g. intestinal lamina propria) tissues for the induction of the IgA response, is well characterized. Recent results provide strong evidence for the presence of a CMIS-independent IgA induction pathway. Two distinct subsets of mucosal IgA-committed B cells termed B-1 and B-2, are associated with CMIS-independence and CMIS-dependent cascades respectively. In some cases, the breakdown of this tightly regulated mucosal immune system leads to pathological responses to different gut environmental antigens. As a result, disorders such as inflammatory bowel disease (e.g. IBD) and allergic gastroenteropathy can be evoked in the gastrointestinal tissues. Recently, many studies have described possible molecular and cellular mechanisms for this dysfunction in the gastrointestinal tissues by using murine models with specific gene manipulation. In this review we summarize recent findings from our group concerning the CMIS-dependent and CMIS-independent IgA induction pathways and gastrointestinal diseases (IBD and intestinal allergic diseases). These observations may provide useful information for the development of new mucosal immune therapy.

Animals↗
PubMed2001

A revisit of mucosal IgA immunity and oral tolerance.

Induction of mucosal immunity by oral immunization with protein antigen alone is difficult: potent mucosal adjuvants, vectors, or other special delivery systems are required. Cholera toxin (CT) has been shown to be an effective adjuvant for the development of mucosal vaccines and, when given with vaccine, induces both mucosal and systemic immune responses via a Th2 cell-dependent pathway. However, and in addition to potential type-I hypersensitivity, a major concern for use of mucosal adjuvants such as CT is that this molecule is not suitable for use in humans because of its inherent toxicity. When we examined the potential toxicity of CT for the central nervous system, both CT and CT-B accumulated in the olfactory nerves/epithelium and olfactory bulbs of mice when given by the nasal route. The development of effective mucosal vaccines for the elderly is also an important issue; however, only limited information is available. When mucosal adjuvanticity of CT was evaluated in aged mice, an early immune dysregulation was evident in the mucosal immune system. The present review discusses these potential problems for effective mucosal vaccine development. Tolerance represents the most common and important response of the host to environmental antigens, including food and commensal bacterial components, for the maintenance of an appropriate immunological homeostasis. We have examined whether Peyer patches could play a more important role for the maintenance of oral tolerance. Using Peyer patch-null mice, we found that mice lacking this gut-associated lymphoid tissue retained their capability to produce secretory IgA antibodies but did not develop normal oral tolerance to protein antigens.

Administration, Inhalation↗
PubMed2001

Ventilator-induced lung injury is associated with neutrophil infiltration, macrophage activation, and TGF-beta 1 mRNA upregulation in rat lungs.

Activated neutrophils contribute to the development of ventilator-induced lung injury (VILI) caused by high-pressure mechanical ventilation. However, exact cellular and molecular mechanisms have not been conclusively studied. Our investigation aimed to examine expression of adhesion molecules by both neutrophils and macrophages in lung lavage fluids of rats with VILI. Further, involvement of proinflammatory (tumor necrosis factor-alpha) and profibrogenetic (transforming growth factor-beta 1) mediators was analyzed at mRNA level in lung tissue. Wistar rats were ventilated by high pressure (45 cm H(2)O of peak inspiratory pressure, n = 23) or low pressure (7 cm H(2)O, n = 13) with 0 positive end-expiratory pressure. After 40 min of comparative ventilation, lung lavage was performed in 20 rats from the experimental group and 10 from the control for immunofluorescence analysis with anti-Mac-1 and anti-ICAM-1 monoclonal antibodies. The lung tissues from remaining rats were subjected to pathological and reverse transcription-polymerase chain reaction examinations. Although there was no significant change of PaO(2) in the low-pressure group, PaO(2) was decreased in the high-pressure group. The high-pressure group also had greater neutrophil infiltration into alveolar spaces, upregulation of CD54 and CD11b on alveolar macrophages, and more transforming growth factor-beta 1 mRNA in lung tissues. Tumor necrosis factor-alpha was not involved in the pathogenesis of the severe VILI observed. Histologic findings also demonstrated more infiltrating neutrophils, destructive change of the alveolar wall, and deposition of matrix in the high-pressure group. These results suggest that a series of proinflammatory reactions and profibrogenetic process may be involved in the course of VILI.

Animals↗
PubMed2001

Glucocorticoid suppresses neutrophil activation in ventilator-induced lung injury.

OBJECTIVE: To investigate, in a rat model, the role of the Mac-1/ICAM-1 pathway and the anti-inflammatory activity of steroid in ventilator-induced lung injury. DESIGN: Prospective, randomized controlled study. SETTING: Animal investigation using Wistar rats. INTERVENTION: Rats in three randomly assigned groups of 18, a total of 54 animals, were subject to the following: Two groups received high peak inspiratory pressure (35 cm H2O) ventilation after pretreatment with methylprednisolone (high-methylprednisolone group) or pretreatment with methylprednisolone vehicle (high-vehicle group). The third group of animals received low peak inspiratory pressure (7 cm H2O) ventilation after pretreatment with methylprednisolone vehicle (low-vehicle group). Except for animals previously killed to establish baseline values, after 40 mins of mechanical ventilation, the animals in each group were killed. Some animals provided histological samples, and the rest received total lung lavage. MEASUREMENT: We measured flow cytometry of lavage fluid, cell counts of tissue samples, and pressure-volume curves before and after mechanical ventilation. RESULTS: In the groups that received high peak inspiratory pressure ventilation, both the number of neutrophils that infiltrated the lungs and the expression of Mac-1 and ICAM-1 on neutrophils and macrophages increased significantly more than in the low-vehicle group. Static lung compliance was reduced in the high peak inspiratory pressure groups. In the high peak inspiratory pressure groups, there were significantly fewer neutrophils in samples from the high-methylprednisolone group (0.412 +/- 0.1 x 10(5)) than from the high-vehicle group (1.10 +/- 0.1 x 10(5); p < .05). The high-vehicle group showed greater expression of CD11b on neutrophils, but this was significantly decreased by methylprednisolone (mean fluorescence intensity: high-vehicle, 118.4 +/- 34.3; high-methylprednisolone, 25.8 +/- 4.2; p < .05). The lung mechanics measured by pressure-volume curve analysis were deteriorated less in the high-methylprednisolone group. CONCLUSION: Our study suggests that a neutrophil-endothelium interaction via the Mac-1/ICAM-1 pathway is involved in the activation and recruitment of neutrophils in ventilator-induced lung injury. Activation and recruitment of neutrophils were lessened by pretreatment with methylprednisolone, which might have contributed to the improvement of lung dysfunction after mechanical ventilation.

Animals↗
PubMed2001

Immunoglobulin A (IgA) responses and IgE-associated inflammation along the respiratory tract after mucosal but not systemic immunization.

The purpose of the present study was to determine the extent of immunologic responses, particularly immunopathologic responses, within the upper and lower respiratory tracts after intranasal immunization using the mucosal adjuvant cholera toxin (CT). BALB/c mice were nasally immunized with influenza virus vaccine combined with CT. The inclusion of the mucosal adjuvant CT clearly enhanced generation of antibody responses in both the nasal passages and lungs. After nasal immunization, antigen-specific immunoglobulin A (IgA) antibody-forming cells dominated antibody responses throughout the respiratory tract. However, IgG responses were significant in lungs but not in nasal passages. Furthermore, parenteral immunization did not enhance humoral immunity in the upper respiratory tract even after a nasal challenge, whereas extrapulmonary lymphoid responses enhanced responses in the lung. After nasal immunization, inflammatory reactions, characterized by mononuclear cell infiltration, developed within the lungs of mice but not in nasal passages. Lowering dosages of CT reduced, but did not eliminate, these adverse reactions without compromising adjuvancy. Serum IgE responses were also enhanced in a dose-dependent manner by inclusion of CT. In summary, there are differences in the generation of humoral immunity between the upper respiratory tract and the lung. As the upper respiratory tract is in a separate compartment of the immune system from that stimulated by parenteral immunization, nasal immunization is an optimal approach to generate immunity throughout the respiratory tract. Despite the promise of nasal immunization, there is also the potential to develop adverse immunopathologic reactions characterized by pulmonary airway inflammation and IgE production.

Administration, Intranasal↗
PubMed2001

New insights into mechanism of inflammatory and allergic diseases in mucosal tissues.

The gastrointestinal immune system is a major component of the mucosal barrier to foreign antigens including microbial and dietary antigens. Under normal circumstances, the mucosal immune system employs tightly regulated dynamic mucosal intra- and internets for the maintenance of an appropriate immunological balance between the host and gut environments. For example, mucosally induced tolerance is usually induced against enteric commensal bacterial and/or dietary antigens. However, in some cases, the break down of these tightly regulated mucosal immune responses led to hyper-responsiveness against these gut environmental antigens. To this end, numerous disorders could evoke in the gastrointestinal tissues, such as inflammatory bowel disease (IBD) and allergic gastroenteropathy. Recently, many studies have described possible molecular and cellular mechanisms of those dysfunctions in the gastrointestinal tissues. In this review, we have briefly summarized some of the current interesting and exciting findings for gastrointestinal diseases, especially IBD and intestinal allergic diseases from our group, which can be applied for the development of new mucosal immune therapy.

Animals↗
PubMed2000

Alteration of V beta usage and cytokine production of CD4+ TCR beta beta homodimer T cells by elimination of Bacteroides vulgatus prevents colitis in TCR alpha-chain-deficient mice.

A major pathogenic factor for the development of inflammatory bowel disease (IBD) is the breakdown of the intestinal homeostasis between the host immune system and the luminal microenvironment. To assess the potential influence of luminal Ags on the development of IBD, we fed TCR alpha(-/-) mice an elemental diet (ED). ED-fed TCR alpha(-/-) mice showed no pathologic features of IBD, and their aberrant mucosal B cell responses were suppressed. Similar numbers of CD4(+), TCR betabeta homodimer T cells (betabeta T cells) were developed in the colonic mucosa of ED-fed mice; however, Th2-type cytokine productions were lower than those seen in diseased regular diet (RD)-fed mice. The higher cytokine production in diseased RD-fed mice could be attributed to the high incidence of Bacteroides vulgatus (recovered in 80% of these mice), which can induce Th2-type responses of colonic CD4(+), betabeta T cells. In contrast, ED-fed TCR alpha(-/-) mice exhibited a diversification of Vbeta usage of betabetaT cell populations from the dominant Vbeta8 one associated with B. vulgatus in cecal flora to Vbeta6, Vbeta11, and Vbeta14. Rectal administration of disease-free ED-fed mice with B. vulgatus resulted in the development of Th2-type CD4(+), betabeta T cell-induced colitis. These findings suggest that the ED-induced alteration of intestinal microenvironments such as the enteric flora prevented the development of IBD in TCR alpha(-/-) mice via the immunologic quiescence of CD4(+), betabeta T cells.

Administration, Rectal↗
PubMed2000

Evidence for early aging in the mucosal immune system.

Despite recent advances in the cellular and molecular analysis of induction and regulation of mucosal immune responses, little is yet known about differences which occur in aging. To address this important issue, we have compared the mucosal and systemic immune responses of aged (12- to 14-mo- or 2-year-old) and young adult (6- to 8-wk-old) C57BL/6 mice. Both aged and young mice were immunized weekly with three oral doses of 1 mg of OVA and 10 microg of cholera toxin (CT) as mucosal adjuvant. Both groups of mice over 1 or 2 years of age showed reduced levels of Ag-specific mucosal or systemic immune responses at day 21. An Ag-specific B cell enzyme-linked immunospot assay confirmed these results at the cellular level. When the Ag-induced cytokine responses were examined at both protein and mRNA levels, CD4(+) T cells from spleen and Peyer's patches of young adult mice revealed elevated levels of IL-4 production; however, these cytokine responses were significantly diminished in aged mice. In contrast to mucosal immunization, mice s. c. immunized with OVA plus CT resulted in impaired OVA-specific but intact CT B subunit-specific immune responses in 12- to 14-mo-old mice although the responses to both Ags were depressed in 2-year-old mice. These results provide the first evidence that the development of age-associated alterations possibly occurs earlier in the mucosal immune system than in the systemic immune compartment.

Adjuvants, Immunologic↗
PubMed2000

Characterization of mucoadhesive microspheres for the induction of mucosal and systemic immune responses.

In the present study, mucoadhesive polymer-dispersed microspheres (MS) were examined as a potential mucosal vaccine carrier. A major focus of the study was aimed at directly assessing the influence of antigen release and persistence in the mouse small intestine for the induction of mucosal and systemic immune responses. BALB/c mice were immunized with various forms of MS containing chicken egg ovalbumin (OVA) by administration into the duodenum. No detectable anti-OVA immune responses were observed following the administration of OVA alone or that of MS without mucoadhesive polymer (MS-0). MS-10 containing 10% mucoadhesive polymer rapidly released OVA and hardly induced anti-OVA antibody responses in either serum or fecal extracts. In contrast, MS-8 and MS-6 (with 8 and 6% mucoadhesive polymer) showed controlled release of OVA, which elicited strong OVA-specific IgG and IgA responses in serum and fecal extracts, respectively. Additionally, the strongest immune responses were induced in mice immunized with MS-8, which had both the optimal release-profile of OVA and the longest persistence in the small intestine. These findings indicate that antigen movement in the small intestine is an important factor and that appropriate microsphere forms with mucoadhesive polymers might be useful candidates as mucosal vaccine carriers.

Adhesives↗
PubMed2000

IL-15 and IL-15 receptor selectively regulate differentiation of common mucosal immune system-independent B-1 cells for IgA responses.

We show in this report a new regulatory role for IL-15 and IL-15R in the development of B-1 cells and their differentiation into IgA-producing cells. Mucosal IgA levels were found to be inhibited by anti-IL-15 mAb treatment in vivo, but enhanced by administration of rIL-15, while serum IgA levels remained unaffected. Mucosal B-1 cells preferentially proliferated in response to IL-15 in vitro. When mucosal B-1 and B-2 cells were separated into surface (s)IgM(+)sIgA(-) and sIgM(-)sIgA(+) fractions, IL-15R-specific mRNA was found to be predominant in both sIgM(+)sIgA(-) and sIgM(-)sIgA(+) B-1 cells at a much higher level than B-2 cells. Further, incubation of these different subsets of B-1 and B-2 cells with IL-15 resulted in greater enhancement of the corresponding receptor expression by B-1 subset when compared with B-2 fraction. Interestingly, de novo isolated sIgM(+)sIgA(-) B-1, but not sIgM(+)sIgA(-) B-2, cells were already class-switched cells because the germline Calpha transcript was detected and was then further enhanced by IL-15. IL-15 also supported differentiation of both sIgM(+)sIgA(-) and sIgM(-)sIgA(+) B-1 cells into IgA-producing cells. Taken together, these findings suggest that IL-15 is a critically important cytokine for the differentiation of both sIgM(+),IgA(-) and sIgM(-)sIgA(+) B-1 cells expressing IL-15R into IgA-producing cells in mucosal tissues.

Animals↗
PubMed2000

Enterotoxin adjuvants have direct effects on T cells and antigen-presenting cells that result in either interleukin-4-dependent or -independent immune responses.

In an in vitro study, Escherichia coli heat-labile toxin (LT) was shown to directly affect activated CD4(+) T cells and support interleukin (IL)-5 production in IL-4-deficient (IL-4(-/-)) mice, whereas cholera toxin (CT) did not. Both LT and CT enhanced B7-2 expression on B cells and macrophages. These effects were not influenced by CD40-CD40 ligand cosignaling. Addition of LT- or CT-treated antigen-presenting cells to anti-CD3-triggered CD4(+) T cells resulted in the induction of T cell proliferative responses. Further, these responses were inhibited by anti-B7-2 monoclonal antibody. Cocultivation of CD4(+) T cells with LT- or CT-treated antigen-presenting cells and anti-CD3 enhanced Th1- and IL-4-mediated Th2-type cytokine production. The results from in vitro studies were supported by in vivo studies in IL-4(-/-) mice, in which LT induced mucosal IgA responses but CT did not. Thus, although both LT and CT induce mucosal adjuvant responses via IL-4-dependent Th2-type responses, LT also elicits Th1- and IL-4-independent Th2-type responses.

Animals↗
PubMed2000

Alternate mucosal immune system: organized Peyer's patches are not required for IgA responses in the gastrointestinal tract.

The progeny of mice treated with lymphotoxin (LT)-beta receptor (LTbetaR) and Ig (LTbetaR-Ig) lack Peyer's patches but not mesenteric lymph nodes (MLN). In this study, we used this approach to determine the importance of Peyer's patches for induction of mucosal IgA Ab responses in the murine gastrointestinal tract. Immunohistochemical analysis revealed that LTbetaR-Ig-treated, Peyer's patch null (PP null) mice possessed significant numbers of IgA-positive (IgA+) plasma cells in the intestinal lamina propria. Further, oral immunization of PP null mice with OVA plus cholera toxin as mucosal adjuvant resulted in Ag-specific mucosal IgA and serum IgG Ab responses. OVA-specific CD4+ T cells of the Th2 type were induced in MLN and spleen of PP null mice. In contrast, when TNF and LT-alpha double knockout (TNF/LT-alpha-/-) mice, which lack both Peyer's patches and MLN, were orally immunized with OVA plus cholera toxin, neither mucosal IgA nor serum IgG anti-OVA Abs were induced. On the other hand, LTbetaR-Ig- and TNF receptor 55-Ig-treated normal adult mice elicited OVA- and cholera toxin B subunit-specific mucosal IgA responses, indicating that both LT-alphabeta and TNF/LT-alpha pathways do not contribute for class switching for IgA Ab responses. These results show that the MLN plays a more important role than had been appreciated until now for the induction of both mucosal and systemic Ab responses after oral immunization. Further, organized Peyer's patches are not a strict requirement for induction of mucosal IgA Ab responses in the gastrointestinal tract.

Animals↗