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Biomedical subjects

H Kikutani

Publications and source records attributed to H Kikutani.

At least 19 recordsLinked to original sources
PubMed2004

Biological functions and signaling of a transmembrane semaphorin, CD100/Sema4D.

The semaphorin proteins were identified originally as axonal guidance factors functioning during neuronal development. In addition to this function, several semaphorins play diverse roles outside the nervous system. The class 4 semaphorin CD100/Sema4D, which utilizes plexin-B1 and CD72 as receptors, exerts important biological effects on a variety of cells, including the neuronal, epithelial and immune cells. Here, we review recent advances exploring the molecular mechanisms governing the biological functions of CD100/Sema4D.

Animals↗
PubMed2003

Increased susceptibility to airway responses in CD40-deficient mice.

The interaction between CD40 and its ligand (CD154) is crucial for IL-12 production and effective humoral immunity such as IgE production. Although the interaction seems to play a crucial role in asthmatic inflammation, previous studies investigating the role of the CD40 and CD154 interaction in experimental animal models of asthma are complicated due to multistep reactions in developing asthma. Here, in order to investigate the role of CD40 in the effector phase in the development of airway responses, we used CD40-deficient mice backcrossed with mice transgenic for an ovalbumin (OVA)-specific TCR (TCRtg). Using intranasal OVA administration followed by aerosol inhalation of OVA, greater airway hyperreactivity and eosinophilia in bronchoalveolar lavage fluid (BALF) were observed in CD40-deficient mice backcrossed with TCRtg mice (CD40-/-/ TCRtg mice), compared with control littermates (CD40+/+/ TCRtg mice). CD4+ helper T cell subset analysis of lung draining lymph nodes revealed that the Th1 component was significantly decreased in CD40-/-/ TCRtg mice. Airway hyperreactivity and airway eosinophilia significantly correlated with the predomination of Th2 cells. Cytokine measurements in BALF also showed decreased IL-12 and the predominance of Th2 cells in CD40-/-/ TCRtg mice. These results suggest that CD40 may play a protective role in developing asthma in the phase after establishing specific memory T cells through the regulation of the balance between Th1 and Th2 cells presumably via induction of IL-12.

Animals↗
PubMed2001

Enhanced immune responses in transgenic mice expressing a truncated form of the lymphocyte semaphorin CD100.

CD100/Sema4D is a 150-kDa transmembrane protein that belongs to the semaphorin family. Binding of CD100 to CD72 enhances the immune response by turning off the negative signaling effects of CD72. To investigate the physiological functions of CD100 in vivo, we generated transgenic mice expressing a truncated form of CD100. A large amount of the soluble form of CD100 was detected in the sera of mice expressing a truncated form of CD100, although the amount of CD100 was only slightly elevated on the surface of B cells. In the mutant mice the development of conventional B and T cells appeared normal in terms of the surface marker phenotypes, while the number of CD5(+) B-1 cells in the peritoneal cavity increased in comparison with wild-type mice. In vitro proliferation and Ig production of B cells in response to CD40 stimulation were considerably enhanced in mice expressing a truncated form of CD100. Additionally, in vivo both Ab responses against T cell-dependent Ags and generation of Ag-specific T cells were enhanced. Furthermore, introduction of the CD100-transgene could restore in vitro B cell responses as well as in vivo Ab production against T cell-dependent Ag in CD100-deficient mice. Collectively, these results not only indicate that CD100 has an important role in the immune system, but also that the soluble form of CD100 released from the cell surface can exert functions in vivo.

Animals↗
PubMed2001

Functional soluble CD100/Sema4D released from activated lymphocytes: possible role in normal and pathologic immune responses.

CD100/Sema4D is a 150-kd transmembrane protein that belongs to the semaphorin family. The interaction of CD100 with CD72 is critical for the immune system. In CD100-deficient mice, the production of specific antibodies against T-cell-dependent antigens is severely impaired, but not against T-cell-independent antigens. Here, a functional soluble CD100 protein (sCD100) released from activated lymphocytes is reported. sCD100 was detected in culture supernatants of activated lymphocytes. Either affinity-purified from supernatants of activated T-cells, or produced as a recombinant sCD100 protein consisting of the extracellular region of the mouse CD100 fused to the human IgG1 Fc (CD100-Fc), sCD100 significantly enhanced CD40-induced B-cell responses. Furthermore, sCD100 was detected either in sera of mice immunized with T-cell-dependent antigens, or in sera of MRL/lpr mice, but not in sera of mice immunized with T-cell-independent antigens. A significant correlation was observed between the level of sCD100 and the titer of autoantibodies in the serum of MRL/lpr mice. This study's findings suggest a potential role for sCD100 in immune responses, including production of antibody, and autoimmune diseases. (Blood. 2001;97:3498-3504)

Animals↗
PubMed2001

Increased T cell autoreactivity in the absence of CD40-CD40 ligand interactions: a role of CD40 in regulatory T cell development.

Mutations in the CD40 ligand (CD40L) gene lead to X-linked immunodeficiency with hyper-IgM, which is often associated with autoimmune diseases. To determine the contribution of defective CD40-CD40L interactions to T cell autoreactivity, we reconstituted CD40-CD40L interactions by transferring T cells from CD40-deficient mice to syngenic athymic nude mice and assessed autoimmunity. T cells from CD40-deficient mice triggered autoimmune diseases accompanied with elevations of various autoantibodies, while those from wild-type mice did not. In CD40-deficient mice, the CD25(+) CD45RB(low) CD4(+) subpopulation which regulates T cell autoreactivity was markedly reduced. CD40-deficient APCs failed to induce T regulatory cells 1 producing high levels of an inhibitory cytokine, IL-10 in vitro. Furthermore, autoimmune development was inhibited when T cells from CD40-deficient mice were cotransferred with CD45RB(low) CD4(+) T cells from wild-type mice or with T regulatory cells 1 induced on CD40-expressing APCs. Collectively, our results indicate that CD40-CD40L interactions contribute to negative regulation of T cell autoreactivity and that defective interactions can lead to autoimmunity.

Animals↗
PubMed2001

Dendritic cell longevity and T cell persistence is controlled by CD154-CD40 interactions.

Inflammatory mediators facilitate the maturation of dendritic cells (DC), enabling them to induce the activation, proliferation and differentiation of cognate T cells. The role of CD40 on DC and CD154 on T cells has been studied by the co-adoptive transfer of antigen-pulsed DC and TCR-transgenic (Tg) T cells in vivo. It is shown that in the absence of CD40-CD154 interactions, initial Tg T cell expansion occurs in vivo, but over time, T cell expansion cannot be sustained. The basis for the demise of the T cell population is likely due to the disappearance of the antigen-pulsed DC in the draining lymph nodes when CD154-CD40 interactions are interrupted. These findings show that both T cell and DC persistence in vivo is dependent on CD40-CD154 interactions. In addition to the physical persistence of the DC, CD40 triggering of DC also greatly increases the period for which they can productively present antigen to Tg T cells. Hence DC persistence and antigen-presenting cell capacity are both dependent on CD40 signaling. While TNF-alpha can mature DC as measured by a variety of criteria, the unique capacity of CD40 signaling to sustain T cell responses and induce DC maturation is underscored by the inability of TNF-alpha to rescue the immune deficiency of CD40(-/-) DC. Hence, the profound impact of CD154 deficiency on cell-mediated immunity may be due to its ability to limit the duration of antigen presentation in vivo and cause the premature demise of antigen-specific T cells.

Adoptive Transfer↗
PubMed2001

The CD100-CD72 interaction: a novel mechanism of immune regulation.

CD100 is a 150 kDa transmembrane protein that belongs to the semaphorin family. Many members of the semaphorin family are known to play crucial roles in axon guidance, acting as chemorepulsive factors during neuronal development. CD100 is the first member of the semaphorin family for which crucial roles in the immune system have been identified. Although plexin-B1 has been shown to be the receptor for CD100 in nonlymphoid tissues, CD72 functions as its receptor in lymphoid tissues. CD100 plays a nonredundant role in the immune response by a unique mechanism that involves switching off the negative signals mediated by CD72.

Animals↗
PubMed2000

Abolition of anti-glomerular basement membrane antibody-mediated glomerulonephritis in FcRgamma-deficient mice.

Several recent studies have demonstrated the central role of Fc receptors (FcR) rather than the complement system in triggering hypersensitivity reactions. We investigated the role of FcR for IgG (FcgammaR) using a murine model of accelerated anti-glomerular basement membrane (GBM) antibody-mediated glomerulonephritis as a representative of type II hypersensitivity diseases. Intravenous injection of rabbit anti-GBM antibody after preimmunization with normal rabbit IgG induced proteinuria and azotemia in wild-type C57BL/6 and CD40(+/-) mice but not in FcR gamma chain (FcRgamma)(-/-) mice or CD40(-/-) mice. Light microscopic findings revealed marked tissue damage in the glomeruli of wild-type C57BL/6 and CD40(+/-) mice. However, no tissue damage except polymorphonuclear cell infiltration was observed in the glomeruli of FcRgamma(-/-) mice. The glomeruli of CD40(-/-) mice were almost normal. Immunohistochemistry revealed the binding of rabbit IgG to the GBM in all mice injected with anti-GBM antibody. However, depositions of mouse IgG and complement to the glomeruli were not observed in CD40(-/-) mice, and deposition of fibrin was not observed in FcRgamma(-/-) or CD40(-/-) mice. These findings suggest that FcgammaR may initiate anti-GBM antibody-mediated renal disease. We conclude that FcgammaR rather than the complement system is critically involved in the development of type II hypersensitivity diseases.

Animals↗
PubMed2000

Identification of CD72 as a lymphocyte receptor for the class IV semaphorin CD100: a novel mechanism for regulating B cell signaling.

We have identified the lymphocyte semaphorin CD100/Sema4D as a CD40-inducible molecule by subtractive cDNA cloning. CD100 stimulation significantly enhanced the effects of CD40 on B cell responses. Administration of soluble CD100 markedly accelerated in vivo antigen-specific antibody responses. CD100 receptors with different binding affinities were detected on renal tubular cells (K(d) = approximately 1 x 10(-9)M) and lymphocytes (K(d) = approximately 3 x 10(-7)M). Expression cloning revealed that the CD100 receptor on lymphocytes is CD72, a negative regulator of B cell responsiveness. CD72 thus represents a novel class of semaphorin receptors. CD100 stimulation induced tyrosine dephosphorylation of CD72 and dissociation of SHP-1 from CD72. Our findings indicate that CD100 plays a critical role in immune responses by the novel mechanism of turning off negative signaling by CD72.

Animals↗
PubMed2000

The class IV semaphorin CD100 plays nonredundant roles in the immune system: defective B and T cell activation in CD100-deficient mice.

The class IV semaphorin CD100/Sema4D differentially utilizes two distinct receptors: plexin-B1 in nonlymphoid tissues, such as brain and kidney, and CD72 in lymphoid tissues. We have generated CD100-deficient mice and demonstrated that they have functional defects in their immune system, without apparent abnormalities in other tissues. The number of CD5(+) B-1 cells was considerably decreased in the mutant mice, whereas conventional B cells and T cells appeared to develop normally. In vitro proliferative responses and immunoglobulin production were reduced in CD100-deficient B cells. The humoral immune response against a T cell-dependent antigen and in vivo priming of T cells were also defective in the mutant mice. These results demonstrate nonredundant and essential roles of CD100-CD72 interactions in the immune system.

Animals↗
PubMed2000

CD23 exhibits negative regulatory effects on allergic sensitization and airway hyperresponsiveness.

The effects of an anti-CD23 monoclonal antibody (B3B4) in CD23-deficient and CD23-overexpressing mice were compared in a murine model of allergic sensitization. After sensitization and challenge with OA, mice developed increased serum levels of OA-specific IgE and IgG(1) with airway eosinophilia and AHR when compared with nonsensitized animals. Anti-CD23 treatment was studied under two protocols: 10-d OA aerosol exposure and intraperitoneal sensitization followed by aerosol challenge. In both protocols anti-CD23 significantly reduced IgE and IgG(1) levels, abolished eosinophilia, and normalized AHR in BALB/c and wild-type CD23+/+ mice but not in CD23-/- mice. These changes were associated with increases in IFN-gamma and decreases in IL-4 production, suggesting that CD23 binding may affect not only IgE production but also the Th1/Th2 imbalance during the development of allergic AHR. Absence of CD23 in gene-deficient mice significantly enhanced OA-specific IgE and IgG(1) levels, airway eosinophilia, and AHR when compared with CD23+/+ wild-type littermates after sensitization and airway challenge. Sensitized and challenged CD23 transgenic mice also developed eosinophilic airway inflammation and methacholine hyperresponsiveness. However, the extent of AHR, BAL, and tissue eosinophilia in these animals showed a significant negative correlation with levels of CD23 expression on splenic T and B cells, demonstrating a limiting role of CD23 in the development of allergic AHR.

Animals↗
PubMed2000

Genetic and immunological basis of autoimmune diabetes in the NOD mouse.

The non-obese diabetic (NOD) mouse is an animal model of human insulin-dependent diabetes mellitus (IDDM). Most NOD mice show insulitis at several weeks of age, and 60-90% of the female mice develop overt diabetes after 20-30 weeks of age. NOD mice share many features of human IDDM. As in human IDDM, the disease development in NOD mice is controlled by a number of disease susceptibility or resistant genes (Idds), including the major histocompatibility complex locus. Cumulative evidence suggests that Thl CD4+ T cells play a critical role in the autoimmune process leading to beta cell destruction. In addition to CD4+ T cells, CD8+ cells and B cells also participate in the pathogenesis. There are several candidate antigens recognized by autoreactive T cells such as glutamic acid decarboxylase (GAD), insulin and heat shock protein (HSP) 60. Treatment by these antigens suppresses IDDM development in NOD mice, suggesting that they may initiate the autoimmune process of NOD mice.

Animals↗
PubMed1999

CD4+ T cell responses to CD40-deficient APCs: defects in proliferation and negative selection apply only with B cells as APCs.

During T-APC interactions in vivo, interfering with CD40-CD154 interactions leads to reduced T cell priming, defects in effector function, and, in some cases, T cell tolerance. As shown here, however, presentation of conventional peptide Ags by CD40-deficient spleen APC in vitro leads to normal CD4+ T cell proliferative responses. By contrast, responses to the same peptides presented by purified B cells were markedly reduced in the absence of CD40. Thus, the requirement for CD40-CD154 interactions appears to be strongly influenced by the type of APC involved. Analysis of responses to endogenous superantigens, which are known to be strongly dependent on B cells for presentation, indicated that CD4+ responses to strong Ags are less dependent on CD40 than are responses to weak Ags. Similar findings applied to negative selection in the thymus. Thus, deletion of potentially autoreactive cells depended on CD40 expression when B APC were involved, and this requirement was most pronounced when negative selection was directed to weak Ags.

Animals↗
PubMed1999

Mimicry of CD40 signals by Epstein-Barr virus LMP1 in B lymphocyte responses.

The effect of the Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) on the activation and differentiation of normal B cells was investigated. B cells of transgenic mice expressing LMP1 under the control of immunoglobulin promoter/enhancer displayed enhanced expression of activation antigens and spontaneously proliferated and produced antibody. Humoral immune responses of LMP1 transgenic mice in CD40-deficient or normal backgrounds revealed that LMP1 mimics CD40 signals to induce extrafollicular B cell differentiation but, unlike CD40, blocks germinal center formation. Thus, these specific properties of LMP1 may determine the site of primary B cell infection and the state of infection in the natural course of EBV infection, whereas subsequent loss of LMP1 expression may affect the site of persistent latent infection.

Animals↗
PubMed1999

CD40-deficient mice infected with the defective murine leukemia virus LP-BM5def do not develop murine AIDS but produce IgE and IgG1 in vivo.

CD40-deficient mice, when inoculated with the LP-BM5def murine retorvirus, become infected and show virus expression similar to wild-type mice. However, unlike the wild-type mice, CD40-deficient mice do not develop symptoms of immunodeficiency, lymphoproliferative disease and the typical histological changes in the lymphoid tissue. These results show that the CD40-CD40 ligand (CD40L) interaction in vivo is essential for anergy induction and the subsequent development of immunodeficiency and pathologic expansion of lymphocytes. Infected CD40-deficient mice and their littermates express a similar pattern of cytokine mRNA, which is not biased towards a Th2 phenotype. Nevertheless, hypergammaglobulinemia is induced in infected wild-type and CD40-deficient mice. Surprisingly, murine AIDS infection even induces IgE production in CD40-deficient mice in vivo. Our data demonstrate that antibody class switch to IgE and IgG1 can be induced by a retroviral infection in vivo even in the absence of CD40-CD40L interaction and an apparent switch to a Th2 cytokine production.

Animals↗
PubMed1999

From systemic T cell self-reactivity to organ-specific autoimmune disease via immunoglobulins.

Rheumatoid arthritis is a common and debilitating autoimmune disease whose cause and mechanism remain a mystery. We recently described a T cell receptor transgenic mouse model that spontaneously develops a disease with most of the clinical, histological, and immunological features of rheumatoid arthritis in humans. Disease development in K/BxN mice is initiated by systemic T cell self-reactivity; it requires T cells, as expected, but B cells are also needed, more surprisingly. Here, we have identified the role of B cells as the secretion of arthritogenic immunoglobulins. We suggest that a similar scenario may unfold in some other arthritis models and in human patients, beginning with pervasive T cell autoreactivity and ending in immunoglobulin-provoked joint destruction.

Adoptive Transfer↗