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T Mizuochi

Publications and source records attributed to T Mizuochi.

At least 55 records · Page 3Linked to original sources
PubMed1996

A novel human serum lectin with collagen- and fibrinogen-like domains that functions as an opsonin.

Collectins are C-type animal lectins with both collagenous and carbohydrate recognition domains and are involved in the first line host defense against pathogens. We report here a novel Ca(2+)-dependent and GlcNAc-binding lectin consisting of subunits of 35 kDa (P35) with a collagen-like sequence. When P35 is isolated from human serum, it forms a homopolymer by means of intermolecular disulfide bonding, as is the case with collectins. P35 cDNA was cloned from a human liver cDNA library, and the deduced amino acid sequence of 313 residues revealed that the mature form of P35 consists mainly of collagen- and fibrinogen-like domains. The latter contained two potential Ca(2+)-binding sites that may be involved in carbohydrate binding. The overall sequence of P35 was highly homologous to porcine ficolins alpha and beta. Northern blots of various human tissues showed that the major product of the 1.3-kilobase-long P35 transcript is expressed in liver. P35 enhanced phagocytosis of Salmonella typhimurium by neutrophils, suggesting an opsonic effect via the collagen region. P35 was found to bind to GlcNAc-conjugated bovine serum albumin, a neoglycoprotein, as well as to neoglycolipids containing complex-type oligosaccharides derived from glycoproteins, suggesting that P35 recognizes GlcNAc residues such as those found in microbial glycoconjugates and complex-type oligosaccharides. Therefore, P35 represents a new type of GlcNAc-binding lectin with structural and functional similarities to collectins involved in innate immunity.

Acetylglucosamine↗
PubMed1996

Difference in antigen presentation pathways between cortical and medullary thymic epithelial cells.

Antigen presentation by thymic epithelial cells (TEC) to T cells that undergo maturation is one of the major events in the selection of the T cell repertoire. We have already reported that medullary TEC lines (mTEC) established from newborn C57BL/6 (H-2b) mice are able to present a soluble antigen, ovalbumin (OVA), to OVA-specific, I-Ab restricted helper T cell lines but cortical TEC (cTEC) lines are not (Mizuochi, T. et al., J. Exp. Med. 1992. 175: 1601). In this report, to clarify the cause of this difference, we analyzed the biochemical nature as well as the distribution of both major histocompatibility complex (MHC) class II molecules and invariant chains (Ii) in both TEC by immunoprecipitation and laser confocal scanning microscopic analysis, as well as the expression of mRNA encoding H-2Ma or H-2Mb. Our results demonstrate that cTEC and mTEC are both able to present peptide antigens to peptide-specific, I-Ab-restricted helper T cell hybridoma and are able to present class II MHC alloantigens to an I-Ab-specific T cell line, that mRNA for H-2Ma and H-2Mb are expressed in both TEC, that cTEC and mTEC apparently incorporate tetramethylrhodamine isothiocyanate-labeled OVA in the same manner, and that the SDS-stable MHC class II molecules, onto which peptides were loaded, are formed in both cTEC and mTEC. However, these molecules were more rapidly degraded in mTEC than in cTEC. In addition, two Ii-derived polypeptides of approximately 21 kDa and 10 kDa were precipitated by the anti-class II monoclonal antibody Y3P; 10-kDa polypeptides were detected in the both TEC, while 21-kDa polypeptides were detected only in cTEC. Finally, beta chains of MHC class II with less sialylated oligosaccharides were precipitated from the cell surface of cTEC. Taken together, these results suggest that there are substantial differences in the antigen-presenting pathways of cTEC and mTEC, and these difference might be responsible for T cell selection events in the thymus.

Animals↗
PubMed1996

[Allo-cytotoxic T lymphocyte responses in corneal allografted mice treated with monoclonal antibodies to adhesion molecules].

Corneal transplantation was performed by grafting C3H/He donor corneas into BALB/c corneal beds. The allografted mice were injected either with 0.5 mg/day of anti-very late antigen (VLA)-4 antibody, anti-leukocyte function-associated antigen (LFA)-1 antibody, or 0.25 mg/day each of both antibodies on days -2, 0, 1, 3, 5, and 7. After 3 weeks, cytotoxic T lymphocyte (CTL) responses to donor alloantigens were assessed. Splenocytes in the allografted mice without treatment demonstrated greater CTL responses that those in naive mice. CTL responses were depressed in mice treated with either anti-LFA-1 alone or a combination of anti-LFA-1 and anti-VLA-4 antibodies as compared with splenocytes from allografted mice without treatment. These data suggest that CTLs play significant roles in eliciting immune response to corneal allografts.

Animals↗
PubMed1995

[New anti-HIV drug which binds the oligosaccharides of HIV envelope glycoprotein].

The virion surface of the human immunodeficiency virus (HIV-1) is covered with an envelope glycoprotein gp120. Study of the oligosaccharide structures of gp120 suggests that the high mannose type of oligosaccharides are essential for HIV-1 infection. Pradimicin A, an antifungal antibiotic isolated from Actinomadura hibisca, and the derivative BMY-28864 have the ability to inhibit HIV-1 infection in vitro. The inhibitory effect was suppressed by addition of high mannose type oligosaccharides of gp120. BMY-28864 bound directly to gp120, mannose-BSA, and neoglycolipids containing high mannose type oligosaccharides but not to natural mammalian glycoproteins. The binding was Ca2+ dependent and was inhibited by mannose. BMY-28864 is a unique carbohydrate-binding antibiotic which has never been reported. It is possible to block HIV-1 infection by targeting oligosaccharide chains of the envelope glycoprotein.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Structural analysis of N-linked oligosaccharides of equine chorionic gonadotropin and lutropin beta-subunits.

Equine chorionic gonadotropin (eCG) and lutropin (eLH) are composed of alpha- and beta-subunits with an identical amino acid sequence but show different biological activities. To elucidate the molecular difference between these gonadotropins, the structure of the N-linked oligosaccharides of each beta-subunit was determined. N-linked sugar chains, liberated as tritum-labeled oligosaccharides by hydrazinolysis followed by N-acetylation and reduction with NaB3H4, were neutralized by sialidase digestion and/or methanolytic desulfation. Neutralized oligosaccharides were fractionated by sequential chromatography on serial lectin affinity columns and on a Bio-Gel P-4 column. Each oligosaccharide structure was determined by sequential exoglycosidase digestion in conjunction with elution profiles on lectin columns and methylation analysis. Each beta-subunit contained a single N-glycosylation site, but a high degree of microheterogeneity was observed in the structure of its N-linked oligosaccharides. eCG beta contained mono-, bi-, tri-, and tetraantennary complex-type oligosaccharides in a ratio of 3:63:13:1. eCG beta oligosaccharides contained about 16% of the bisecting GlcNAc and about 20% of poly-N-acetyllactosamine structures. Elongation of N-acetyllactosamine units showed a preference to the Man alpha 1-->6 side rather than the Man alpha 1-->3 side. Triantennary chains had only a C-2, 4-branched structure. eLH beta contained only mono- and biantennary complex-type and hybrid-type oligosaccharides in a ratio of approximately 18:67:10. eLH beta also contained bisected structures in about 18%. Oligosaccharides derived from the sulfated fraction of eLH beta contained GalNAc residues at nonreducing termini. Oligosaccharides from the sialylated/sulfated fraction of eLH beta contained both Gal and GalNAc residues at nonreducing termini, and those GalNAc residues were preferentially distributed to the Man alpha 1-->3 side of the trimannosyl core. These results clearly indicate that eCG beta and eLH beta possess structurally distinct N-linked oligosaccharides in addition to different charge groups even though they have a protein moiety identical to each other. Our results suggest that the biological activity of these hormones might be modulated by its terminal charge groups and stem structures of carbohydrate moiety synthesized in different organs.

Amino Sugars↗
PubMed1994

Gene transfer using purified retroviral integrase.

We present a new method of gene transfer into cultured cells using a purified retroviral integrase protein with liposomes. The acceleration rate of transfection by the integrase was increased by a few to ten times. The integrase target sequence containing the 3' end of LTR on the introduced plasmid was necessary for the acceleration, and the orientation of this sequence determined the level of acceleration activity. The analyses of the chromosomal DNAs of each transfectant demonstrated the integration of the introduced plasmid DNA within the integrase-target sequence.

Animals↗
PubMed1994

Influence of H-2 class II antigens on the development of murine AIDS.

Inbred strains of mice differ markedly in their relative susceptibility to the development of lymphoproliferation and immunodeficiency, a syndrome termed mouse AIDS (MAIDS), after infection with the LP-BM5 mixture of murine leukemia viruses (MuLV). The etiologic virus in this mixture is replication defective (BM5def) and encodes only a variant gag protein. Genetic determinants of resistance and susceptibility to induction of MAIDS reside both within and outside the MHC. In strains with C57BL background genes, the MHC haplotypes associated with resistance to disease include d and a, whereas haplotypes b, s, and q are associated with sensitivity. Previous studies showed that MHC class I genes (H-2Dd, H-2Ld) mapping in the D end of H-2 and other genes mapping proximal to the D end determine resistance to MAIDS. This paper examines the nature of these non-D end MHC genes using assays of MHC recombinant and transgenic mice. We demonstrate that expression of E alpha d confers significant resistance to MAIDS, even in mice that do not express H-2Dd/H-2Ld. Unexpectedly, we found that E alpha polymorphisms can significantly influence resistance, with H-2b mice bearing E alpha d as a transgene having greater resistance to MAIDS than mice bearing an E alpha k transgene. E alpha d-mediated resistance to MAIDS was associated with decreased levels of the BM5def genome in splenic DNA, suggesting that E alpha genes exert their effect by enhancing antiviral activity.

Animals↗
PubMed1994

Increased Fas antigen expression in murine retrovirus-induced immunodeficiency syndrome, MAIDS.

The Fas antigen (Fas), which is a cell surface protein belonging to the tumor necrosis factor receptor family, mediates apoptosis. To assess the contribution of Fas to the pathogenesis of retrovirus-induced immunodeficiency, we examined the kinetics of Fas expression on the lymphocytes during the course of murine acquired immunodeficiency syndrome (MAIDS) induced by a defective LP-BM5 murine leukemia virus. The Fas-positive cells were increased in proportion both in alpha beta T cells and B cells with the progression of MAIDS. The appearance of Fas-positive cells in alpha beta T cells preceded those in B cells during the course of MAIDS. Among alpha beta T cells, about half of the Thy1.2+ alpha beta T cells were positive for Fas, while almost all of Thy1.2- CD4+ alpha beta T cells were of the Fas-positive phenotype. The Fas-positive cells in MAIDS mice, especially unique Thy1.2-CD4+ alpha beta T cells, were easily rendered apoptotic by stimulation via Fas, indicating that Fas expressed on the lymphocytes is functional. Furthermore, concomitant infection with Mycobacterium avium in MAIDS mice caused a marked increase in Fas-positive cells accompanied by a severely impaired T cell reactivity to polyclonal stimuli. Taken together, these results suggest that possible participation of the Fas system in the pathogenesis of retrovirus-induced immunodeficiency.

Animals↗
PubMed1994

The cytotoxicity of macrocyclic trichothecenes, roridin A and verrucarin A, on murine T-cells is reduced by Ia-negative splenic adherent cells.

The in vitro effect of macrocyclic trichothecenes, roridin A and verrucarin A, and a non-macrocyclic trichothecene, T-2 toxin, on the concanavalin A-induced murine T-cell blastogenesis was investigated. The macrocyclic trichothecenes inhibited the blastogenesis of both thymocytes and splenocytes, splenocytes being more resistant than thymocytes. Such resistance to macrocyclic trichothecenes was not observed in splenic T-cells separated from the other cell population, nor in splenocytes depleted of adherent cells. In order to find the cell population responsible for resistance, the toxins were incubated with fractionated splenic cells and then cytotoxicity of the supernatants of the incubation mixtures was examined by using T-cell blastogenesis assay. The results showed that the splenocytes depleted of Ia-negative cells had the ability to reduce the cytotoxicity of the macrocyclic trichothecenes, but not that of T-2.

Animals↗
PubMed1994

Analysis of function of a human antigen-presenting cell by xenogeneic interaction with mouse T cells.

A human B cell line, ARH, was transfected with a murine major histocompatibility complex class II gene (I-A(k)). One of the transfectants, ARH5.5, which strongly expresses I-A(k) molecules was found to be capable of presenting soluble antigens to I-A(k)-restricted, antigen-specific murine helper T cell (Th) clones. When ARH5.5 was treated with either chloroquine or paraformaldehyde prior to the antigen pulse, it failed to present a protein antigen, ovalbumin, but retained the ability to present a peptide, indicating that the presentation was dependent on processing. The xenogeneic interaction of co-stimulatory molecules on the human antigen presenting cell (APC) and the murine Th cell was assessed by using antibodies against adhesion molecules. We found that the xenogeneic interaction of LFA-1/ICAM-1 acted as a strong co-stimulator of the antigen presentation by ARH5.5, while that of CD2/LFA-3 had only little stimulatory effect. These results suggest that the interaction between some of the adhesion molecules on APC and Th can cross the species barrier. The experimental system presented here is simple and useful for analyzing human APC function, separately from T cell function, especially when the dysfunction of APC associated with viral infection with human tropism is considered.

Amino Acid Sequence↗
PubMed1994

Both cathepsin B and cathepsin D are necessary for processing of ovalbumin as well as for degradation of class II MHC invariant chain.

The effect of highly selective inhibitors of cathepsins on the processing of ovalbumin (OVA) and the presentation of an OVA-derived antigenic peptide (OVA323-339) by antigen presenting cells (APC) was investigated. Both CA-074 (a specific inhibitor of cathepsin B) and pepstatin A (a specific inhibitor of cathepsin D) showed an inhibitory effect on the IL-2 production from an OVA-specific, I-Ad-restricted helper T (Th) cell clone upon stimulation with OVA presented by the I-Ad-positive APC. In contrast, the presentation of the antigenic epitope, OVA323-339, to the same Th clone was not inhibited by either CA-074 or pepstatin A alone, nor even by the mixture of both inhibitors. When APC were treated with cathepsin inhibitor for 24 h, and then antigen and Th were added to the culture, the presentation of not only OVA but also an OVA-derived antigenic peptide was inhibited by either cathepsin inhibitor alone. In addition, the expression of invariant chain on APC was significantly augmented by the pretreatment of APC with either cathepsin inhibitor. Two main conclusions are drawn from these results. First, not only aspartyl protease, such as cathepsin D, but also thiol protease, such as cathepsin B, is involved in antigen processing by APC. Second, both cathepsin B and cathepsin D are necessary for degradation of the invariant chain (Ii) from the MHC class II alpha beta heterodimer in endosomes in order to express functional MHC class II molecules for binding antigenic peptides.

Animals↗
PubMed1994

An IFN-gamma-dependent pathway plays a critical role in the pathogenesis of murine immunodeficiency syndrome induced by LP-BM5 murine leukemia virus.

The murine acquired immunodeficiency syndrome (MAIDS) caused by a defective murine leukemia virus produces severe immunodeficiency with abnormal lymphoproliferation and hypergammaglobulinemia. The presence of both CD4+ T cells and B cells is critical for the development of this disease. Remarkably elevated mRNA expression for IFN-gamma and IL-10 was observed in spleen cells of C57BL/6 mice starting from the early phase of viral infection. IFN-gamma production was induced by spleen cells from virus-infected mice upon stimulation with concanavalin A or lipopolysaccharide in both the early and late phases of MAIDS progression. When mice that had been passively administered anti-IFN-gamma mAb were infected with the virus, the development and progression of lymphadenopathy, immunodeficiency and elevated levels of serum IgG2a associated with MAIDS were delayed. Treatment with anti-IL-4 or anti-IL-10 mAb in place of anti-IFN-gamma mAb did not induce the delayed progression of MAIDS. These data support the concept that IFN-gamma-dependent pathway may be involved in the development of MAIDS.

Animals↗
PubMed1993

Delayed progression of a murine retrovirus-induced acquired immunodeficiency syndrome in X-linked immunodeficient mice.

The murine acquired immunodeficiency syndrome (MAIDS) caused by defective LP-BM5 murine leukemia virus (MuLV) is a disease that shows severe immunodeficiency with abnormal lymphoproliferation, and hypergammaglobulinemia in susceptible C57BL/6 (B6) mice. To examine the cellular mechanisms of development of MAIDS, we injected LP-BM5 MuLV intraperitoneally into B6 mice bearing the X chromosome-linked immunodeficiency (xid). xid mice lack functionally mature B cells including Ly-1 B cells (also known as B-1 cells). All B6 mice died by 20 wk after LP-BM5 MuLV inoculation. In marked contrast, xid mice have continued to survive without any sign of MAIDS-related symptoms till at least 20 wk after the inoculation. The delayed progression of MAIDS in xid mice appears to depend on xid mutation, according to our experiments using both sexes of (B6.xid x B6)F1 and (B6 x B6.xid)F1 mice. Furthermore, Ly-1 B cells, enriched by a FACS, were shown to integrate the defective genome and appeared to be a major virus-infected B cell population. Our data corroborate that Ly-1 B cells play an important role in the induction and progression of MAIDS.

Animals↗
PubMed1993

Tolerance induction by clonal deletion of CD4+8+ thymocytes in vitro does not require dedicated antigen-presenting cells.

The cellular requirements of T cell tolerance induction in the thymus by clonal deletion was investigated by using an in vitro assay: thymocytes from mice expressing a transgenic TcR specific for lymphocytic choriomeningitis virus (LCMV) and H-2Db were co-cultured with various H-2b cell types as antigen-presenting cells in the presence of the antigenic LCMV peptide. The results revealed that all cell lines examined including embryonic and transformed fibroblasts, melanoma cells, cortical thymic epithelial cells, lymphomas and neuronal cells induced an antigen dose-dependent deletion of CD4+8+ thymocytes. Similarly, highly enriched accessory cell populations from thymus and spleen (macrophages, dendritic and cortical epithelial cells, i.e. thymic nurse cells) could induce antigen-specific depletion of immature CD4+8+ thymocytes. Depending on the cell type examined micromolar to picomolar concentration of LCMV peptide were required to induce deletion. The effectiveness of deletion by the different cell types did not correlate with their major histocompatibility class I expression level; it was, however, influenced by the presence of ICAM-1 adhesion molecules.

Animals↗
PubMed1993

Comparative studies of asparagine-linked sugar chains of immunoglobulin G from eleven mammalian species.

1. Asparagine-linked sugar chains released by hydrazinolysis from IgGs of porcine, equine, bovine, goat, ovine, canine, rabbit, guinea-pig and rat were comparatively analyzed by microsequencing and lectin affinity chromatography. 2. Sugar chains of all IgGs basically consisted of biantennary complex-type oligosaccharides containing 0-2 sialic acid residue(s). More than 70% of the oligosaccharides were neutral, except for guinea-pig IgG, and fucosylated trimannosyl core structures were dominant except for rabbit IgG. Bisecting N-acetylglucosamine residue was absent in porcine and equine IgGs. 3. A large quantity of galactose-less oligosaccharides were present in IgGs of porcine, equine, canine and rat.

Animals↗
PubMed1993

Exocrinopathy resembling Sjögren's syndrome induced by a murine retrovirus.

BACKGROUND: Sjögren's syndrome (SS) is characterized by lymphocytic infiltration into, and destruction of exocrine glands, resulting in dryness of the mouth and eyes. The disease is considered to have an autoimmune etiology, however, its etiopathogenesis remains largely unknown. Recently, retrovirus is suggested to participate in the pathogenesis of SS, because SS-like lesions are reported in HIV infection or in human T cell leukemia virus type I infection. Moreover, human intracisternal A-type retroviral particles are reported to be detected in SS patients. During the course of our study on the histopathology of mice infected with a murine retrovirus, we happened to find SS-like exocrinopathy in those mice. EXPERIMENTAL DESIGN: Four-week-old C57BL/6 (B6) mice were injected intraperitoneally with LP-BM5 murine leukemia virus. This virus is known to induce splenomegaly, lymphadenopathy followed by lymphoid malignancy, and profound immunodeficiency in sensitive strains of mice. From 4 to 16 weeks after the virus inoculation, the infected mice were sacrificed and their submandibular and lacrimal glands were analyzed light and electron microscopically and immunohistochemically. The existence of the virus in the lesion in situ was also analyzed by the same method, and additionally by a polymerase chain reaction method. RESULTS: Periductal lymphocytic infiltration into the submandibular and lacrimal glands was observed in all the virus-infected mice at 4 weeks after the infection and progressed with time. Extraglandular lymphocytic infiltration was also observed in liver, kidney, lung, and pancreas. Immunohistochemical examination revealed that most infiltrating cells into the glands were composed of CD3+ T cells (CD4-dominant), Mac-1+ cells, and B220+ cells. The virus genome was detected in submandibular glands by immunohistochemistry or by polymerase chain reaction. In addition, retroviral particles were secreted into the lumen of exocrine ducts of submandibular glands. CONCLUSIONS: This might be an SS animal model that is induced by a certain defined retrovirus. This experimental system might provide us with valuable information for analyzing the mechanisms of how a retrovirus could induce SS.

Animals↗
PubMed1992

Medullary but not cortical thymic epithelial cells present soluble antigens to helper T cells.

Thymic epithelial cell lines (TECs) were established from newborn C57BL/6 mice. They were classified into two types (medullary and cortical TECs) by using the monoclonal antibody (Th-3) that recognizes the meshwork structure of thymic cortical epithelial cells. Antigen-presenting activity of each TEC was determined by using ovalbumin-specific, I-Ab-restricted helper T cell lines. It was demonstrated that the medullary but not the cortical TECs functioned as antigen-presenting cells. This is the first evidence for the functional difference between the cortical and the medullary TEC.

Animals↗