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Biomedical subjects

T Takai

Publications and source records attributed to T Takai.

At least 55 records · Page 3Linked to original sources
PubMed1999

Deletion of fcgamma receptor IIB renders H-2(b) mice susceptible to collagen-induced arthritis.

Autoimmune diseases, like rheumatoid arthritis, result from a dysregulation of the immune response culminating in hyperactivation of effector cells leading to immune-mediated injury. To maintain an appropriate immune response and prevent the emergence of autoimmune disease, activation signals must be regulated by inhibitory pathways. Biochemical and genetic studies indicate that the type IIB low-affinity receptor for immunoglobulin (Ig)G (FcgammaRIIB) inhibits cellular activation triggered through antibody or immune complexes and may be an important component in preventing the emergence of autoimmunity. To investigate the role of FcgammaRIIB in the development of type II collagen (CII)-induced arthritis (CIA), a model for rheumatoid arthritis in humans, we have examined its contribution in determining the susceptibility to CIA in the nonpermissive H-2(b) haplotype. H-2(b) mice immunized with bovine CII do not develop appreciable disease. In contrast, immunization of the FcgammaRIIB-deficient, H-2(b) mice with bovine CII induced CIA at an incidence of 42.2%. The maximal arthritis index of the FcgammaRIIB-deficient mice developing CIA (6.9 +/- 3.6) was comparable to that of DBA/1 mice (8.6 +/- 1.9), an H-2(q) strain susceptible for CIA induction. IgG1, IgG2a, and IgG2b antibody responses against CII were elevated in the FcgammaRIIB-deficient animals, especially in those mice showing arthritis, but less pronounced than DBA/1 mice. Histological examinations of the arthritic paws from FcgammaRIIB-deficient mice revealed that cartilage was destroyed and bone was focally eroded in association with marked lymphocyte and monocyte/macrophage infiltration, very similar to the pathologic findings observed in DBA/1 mice. These results indicate that a nonpermissive H-2(b) haplotype can be rendered permissive to CIA induction through deletion of FcgammaRIIB, suggesting that FcgammaRIIB plays a critical role in suppressing the induction of CIA.

Animals↗
PubMed1998

Inhibitory and stimulatory functions of paired Ig-like receptor (PIR) family in RBL-2H3 cells.

In this study, we demonstrate potent regulatory function of the murine killer cell inhibitory receptor-like molecules, paired Ig-like receptors (PIRs) or p91, using chimeric receptors expressed on the rat basophilic leukemia cell line RBL-2H3. One of the chimeras, which has the transmembrane and cytoplasmic domain of PIR-B fused to the extracellular portion of type IIB receptor for IgG, was able to inhibit the type I receptor for IgE-mediated degranulation response upon coaggregation. This chimera also suppressed cytoplasmic Ca2+ mobilization in the presence and absence of calcium ion in the extracellular medium. Tyrosine to phenylalanine point mutations at the third and fourth immunoreceptor tyrosine-based inhibitory motif-like sequences of PIR-B attenuated the inhibitory effects on degranulation and on cytoplasmic Ca2+ mobilization, indicating the important role of these tyrosines for the delivery of negative signal. In contrast, the cross-linking of another chimeric receptor composed of the type IIB receptor for IgG extracellular portion and the transmembrane and short cytoplasmic sequence of PIR-A elicited Ca2+ mobilization and degranulation. These results indicate that PIR molecules may regulate cellular functions both positively and negatively.

Animals↗
PubMed1998

Requirement of SH2-containing protein tyrosine phosphatases SHP-1 and SHP-2 for paired immunoglobulin-like receptor B (PIR-B)-mediated inhibitory signal.

Paired immunoglobulin-like receptor B (PIR-B) (p91) molecule has been proposed to function as an inhibitory receptor in B cells and myeloid lineage cells. We demonstrate here that the cytoplasmic region of PIR-B is capable of inhibiting B cell activation. Mutational analysis of five cytoplasmic tyrosines indicate that tyrosine 771 in the motif VxYxxL plays the most crucial role in mediating the inhibitory signal. PIR-B-mediated inhibition was markedly reduced in the SH2-containing protein tyrosine phosphatases SHP-1 and SHP-2 double-deficient DT40 B cells, whereas this inhibition was unaffected in the inositol polyphosphate 5'-phosphatase SHIP-deficient cells. These data demonstrate that PIR-B can negatively regulate B cell receptor activation and that this PIR-B-mediated inhibition requires redundant functions of SHP-1 and SHP-2.

Antigens, CD↗
PubMed1998

Severe motor-dominant neuropathy with IgM M-protein binding to the NeuAcalpha2-3Galbeta- moiety.

We report the occurrence of a relapsing, severe predominantly motor neuropathy in a 75-year-old man with an IGM-K M-protein binding to gangliosides GM2, GM3, GM4, GD1a, GT1b and LM1. Motor nerve conduction velocities were slowed with conduction block. A superficial peroneal nerve biopsy specimen revealed segmental demyelination and remyelination. The patient improved after repeated plasma exchanges, and the antibody titer decreased in association with clinical recovery. This IgM M-protein has a unique, previously unreported binding specificity for terminal NeuAcalpha2-3Galbeta- moiety in common to all gangliosides bound by the antibody except GM2. M-proteins with this affinity may be involved in the pathogenesis of this and other cases of motor-dominant demyelinating neuropathy.

Aged↗
PubMed1998

Association of tyrosine phosphatases SHP-1 and SHP-2, inositol 5-phosphatase SHIP with gp49B1, and chromosomal assignment of the gene.

We have analyzed the molecules participating in the inhibitory function of gp49B1, a murine type I transmembrane glycoprotein expressed on mast cells and natural killer cells, as well as the chromosomal location of its gene. As assessed by SDS-polyacrylamide gel electrophoresis and immunoblot analysis, tyrosine-phosphorylated, but not nonphosphorylated, synthetic peptides matching each of the two immunoreceptor tyrosine-based inhibitory motif (ITIM)-like sequences found in the cytoplasmic portion of gp49B1 associated with the approximately 65-kDa tyrosine phosphatase SHP-1 and approximately 70-kDa SHP-2 derived from RBL-2H3 cells. In addition, the phosphotyrosyl peptide matching the second ITIM-like sequence also bound the approximately 145-kDa inositol polyphosphate 5-phosphatase SHIP. Thus, it has been strongly suggested that the inhibitory nature of gp49B involves the recruitment of SHP-1, SHP-2, and SHIP for the delivery of inhibitory signal to the cell interior upon phosphorylation of tyrosine residues in their ITIMs. The gp49B gene has been found to be in the juxtaposition of its cognate gene, gp49A. The gene pair was shown to locate in the B4 band of mouse chromosome 10. In this region, no conserved linkage homology to human chromosome 19, where the genes for killer cell inhibitory receptors are found, has been identified.

Animals↗
PubMed1998

Radioimmunoassay for TA-0910, a new stable thyrotropin releasing hormone analogue and its metabolite, TA-0910 acid-type, in human plasma and urine.

Radioimmunoassay (RIA) was investigated for the determination of TA-0910 and its main metabolite, TA-0910 acid-type, in human plasma and urine. TA-0910 is a new metabolically stable analogue of thyrotropin releasing hormone (TRH). Antiserum was raised in the rabbit against the 1-fluoro-2,4-dinitrophenyl derivative of TA-0910 or TA-0910 acid-type conjugated to keyhole limpet hemocyanin (KLH). The radioligand was prepared by iodination with 125I of the histidine imidazole ring of TA-0910 or TA-0910 acid-type. Cross-reactivities of anti-TA-0910 or TA-0910 acid-type antiserum for TA-0910, its metabolite and related compounds were low. The calibration range was 0.02-5 ng ml-1 using 100 microliters human plasma or urine. Inter-day variations of TA-0910 and TA-0910 acid-type assay in plasma were 3.5-15.5 and 1.8-9.4%, respectively. The variations of the assay in urine were the same as those in plasma. The recovery of TA-0910 and TA-0910 acid-type spiked in plasma or urine samples was approximately 100%. Furthermore, this method was applied to the determination of TA-0910 and TA-0910 acid-type in human plasma and urine samples, for the evaluation of the pharmacokinetics of TA-0910 in humans. From the results it was demonstrated that he developed RIA was useful for the determination of TA-0910 and TA-0910 acid-type in human plasma and urine, and was applicable to pharmacokinetic studies in humans.

Administration, Oral↗
PubMed1998

Hyposensitization to allergic reaction in rDer f 2-sensitized mice by the intranasal administration of a mutant of rDer f 2, C8/119S.

C8/119S is a mutant of recombinant Der f 2 (rDer f 2), and lacks a disulphide bond possessed by wild-type rDer f 2. In humans and mice, C8/119S has a very weak IgE-binding capacity compared with the wild-type, but possesses a T cell reactivity comparable to that of the wild-type. C8/119S may thus be a safe immunotherapeutic agent for house dust mite allergy. The aim of the present study was to evaluate whether the intranasal administration of C8/119S could suppress an immediate allergic reaction in mice sensitized with wild-type rDer f 2, possessing an allergic activity comparable to native counterparts purified from mite extract. Seven-week-old male A/J mice were immunized with wild-type rDer f 2 four times, and then intranasally administered 0.2-2 microg of wild-type, 0.2-20 microg of C8/119S, or PBS alone, three times a week for 4 weeks. Seven days after the last administration, the mice were examined for an immediate allergic reaction. The animals administered 2 microg of C8/119S (C2.0 group) showed significantly reduced immediate bronchoconstriction provoked by the i.v. injection of 1 and 10 microg of wild-type rDer f 2, compared with the PBS-treated mice. Similar results were obtained when we examined mice 10 weeks after the last administration. The reactions in the other groups given wild-type or C8/119S also tended to decrease in severity in comparison with the animals of the PBS group. The allergic phenotypes of the T cells, B cells, and basophils in the C2.0 group were shifted to that of naive mice without immunization. We conclude that C8/119S has hyposensitizing activities in mice sensitized with wild-type rDer f 2. C8/119S may be useful for immunotherapy of house dust mite allergy.

Administration, Intranasal↗
PubMed1998

Antigen receptor cross-linking by anti-immunoglobulin antibodies coupled to cell surface membrane induces rapid apoptosis of normal spleen B cells.

Cross-linking of surface immunoglobulin (sIg) has been shown to induce either activation or apoptosis of mature B cells presumably depending on the nature of antigens. However, the nature of antigens for induction of mature B-cell apoptosis is not yet fully understood. We cross-linked sIg of mature B cells with various amounts of either anti-Ig antibodies in the soluble form or anti-Ig coupled to erythrocytes or myeloma cells as surrogate membrane-bound antigens. Anti-Ig antibodies coupled to cell surface membrane induced rapid and extensive apoptosis of normal spleen B cells even in the absence of signalling via the Fc receptor. In contrast, soluble anti-Ig induced proliferation or apoptosis of mature B cells depending on the concentration of anti-Ig. The extent of apoptosis induced by soluble anti-Ig was limited compared to that induced by membrane-bound anti-Ig. These results suggest that mature B cells undergo apoptosis or proliferation depending on whether antigens are soluble or membrane-bound and on antigen doses.

Animals↗
PubMed1998

Distinct contribution of Fc receptors and angiotensin II-dependent pathways in anti-GBM glomerulonephritis.

BACKGROUND: The contribution of antibody and/or immune-complex to the pathogenesis of immunologically-mediated glomerulonephritis is not fully understood, although it has been recently clarified that Fc receptors (FcRs) play critical roles in the inflammatory cascade. We therefore re-evaluated the classical model of glomerulonephritis, anti-glomerular basement membrane antibody-induced glomerulonephritis (Anti-GBM GN), from the standpoint of FcRs and also investigated the residual FcR-independent mechanisms. METHODS: We adopted an Anti-GBM GN mouse model that has two strains deficient in the FcR gamma chain [gamma(-/-)] or Fc gammaRIIB [RII(-/-)], and analyzed functional (urinary protein, serum creatinine, BUN) and pathological changes of the glomeruli. For the analyses of FcR-independent mechanisms, several doses of nephrotoxic serum were applied, and then mice were treated either with cobra venom factor or an angiotensin II type 1 receptor antagonist in gamma(-/-) mice. RESULTS: In gamma(-/-) mice, renal injuries were dramatically attenuated with an absence of polymorphonuclear cell (PMN) influx, while RII(-/-) mice suffered accelerated glomerular injuries in spite of a normal PMN influx. In the absence of FcR-dependent effects in gamma(-/-) mice, the FcR-independent pathway lead to chronic renal damage characterized by mesangial proliferation and progressive expansion of mesangial area, with monocyte/macrophage accumulation and with the expression of alpha smooth muscle actin in the mesangial cells and interstitium. Those injuries in gamma(-/-) mice were not attenuated by the decomplementation, but completely abolished by using an angiotensin II type 1 receptor antagonist. CONCLUSIONS: Our results clearly demonstrate that FcRs play a pivotal role in Anti-GBM GN, especially in its acute phase. We further clarified the existence of FcR and complement-independent but antibody-dependent pathway. Furthermore, we found that those pathological changes were strongly related to the renin-angiotensin system.

Actins↗
PubMed1998

Genomic structures and chromosomal location of p91, a novel murine regulatory receptor family.

Recently, we found a novel murine cell-surface glycoprotein, designated as p91, expressed mainly in myeloid cells such as macrophages and mast cells. The molecule has six immunoglobulin-like extracellular domains, a transmembrane segment, and a cytoplasmic tail containing four immunoreceptor tyrosine-based inhibition motif (ITIM) or ITIM-like sequences, resembling the structural features of human killer-cell inhibitory receptors (KIR). Here we show that p91 comprises a polymorphic gene family, harboring one potent inhibitory-type p91 and at least two other p91 genes. Tyrosine-phosphorylated, but not nonphosphorylated, synthetic peptides matching the third ITIM and the fourth ITIM-like sequences, respectively, found in the cytoplasmic portion of p91A, the sole inhibitory-type p91, were associated with the tyrosine phosphatases, SHP-1 and SHP-2. In addition, the phosphotyrosyl peptide matching the third ITIM sequence also bound the inositol 5-phosphatase, SHIP. These results support the notion that p91A may function as an inhibitory cell-surface molecule against cell activation. The p91 genes were shown to be clustered in the proximal region of mouse chromosome 7, a syntenic position of human chromosome 19 where the genes for the KIR family are found. A human cDNA clone cross-hybridizing to a murine p91 probe was isolated from a human spleen cDNA library, and was found to code for a molecule quite similar to members of the immunoglobulin-like transcript (or ILT) family. The gene was found to be located on human chromosome 19q13.3-13.4. These results establish the existence of a novel set of potent regulatory receptors in mouse and man, similar but different from the KIR family.

Amino Acid Sequence↗
PubMed1998

[Development of NIHS Information and Computing Infrastructure (NICI)].

We describe the development of NICI, which we extended during June 1996 to May 1998. The direct lines between our Experimental Stations for Medicinal Plants at Tsukuba and Tsukuba Node for Inter Ministry Network, and newly opened Pharmaceuticals and Medical Devices Evaluation Center at Minato-ku and NIHS at Setagaya-ku in Tokyo, were constructed. Although the main frame in NIHS at Setagaya is not different since May 1996, we provided many databases and useful information on Drugs, Foods and Chemicals, constructing the interface between World Wide Web and databases. Our Home Page was timely updated.

Databases, Factual↗
PubMed1997

Characterization of B cells expressing recombination activating genes in germinal centers of immunized mouse lymph nodes.

Products of recombination activating genes (RAG-1 and RAG-2) involved in the rearrangement of Ig genes have been shown to be expressed only in immature stages of B cells. However, we have recently found that RAG genes were re-expressed in mature mouse B cells activated in vitro and in germinal centers (GCs) of immunized mouse lymph nodes (LNs). Here, we report that RAG transcripts and their proteins were expressed in parallel with the formation of GCs in popliteal LNs from mice immunized in the hind footpads. Immunocytochemical analysis revealed that RAG+ B cells were localized within GCs and were present as apoptotic tingible body cells. RAG expression is not considered a nonspecific result of apoptosis, since apoptotic B cells generated by surface Ig-engagement did not express RAG genes. These results suggest a novel role of RAG products in the differentiation of B cells in GCs.

Animals↗
PubMed1997

Molecular cloning of a novel murine cell-surface glycoprotein homologous to killer cell inhibitory receptors.

We have isolated a cDNA clone encoding a novel murine cell-surface glycoprotein. This polypeptide is predicted to be composed of a signal peptide of 23 amino acids, an extracellular region of 620 amino acids that contains six immunoglobulin-like domains with five potential N-glycosylation sites, a transmembrane sequence of 20 amino acids, and a cytoplasmic tail of 178 amino acids with four sets of sequences similar to the immunoreceptor tyrosine-based inhibition motif. The relative molecular mass of the mature polypeptide is calculated to be 90,520 Da. The polypeptide, designated as p91, shows striking homologies to human killer cell inhibitory receptors, a murine gp49B1 protein, a bovine Fcgamma2 receptor, and a human Fcalpha receptor. The mRNA of p91 was especially abundant in murine macrophages. Western blot analysis using p91-specific anti-peptide sera detected a 130-kDa polypeptide in macrophages. Surface biotinylation and immunoprecipitation analysis verified the surface expression of the translation products on COS-1 cells transfected with the p91 cDNA, but the cells failed to show any Fc binding activity.

Amino Acid Sequence↗
PubMed1997

Determination of the N- and C-terminal sequences required to bind human IgE of the major house dust mite allergen Der f 2 and epitope mapping for monoclonal antibodies.

B cell epitopes of the major house dust mite allergen Der f 2 from Dermatophagoides farinae were analysed using deletion mutants of Der f 2 expressed as fusion proteins in Escherichia coli. The reactivities of these partial Der f 2 molecules to human anti-mite IgE antibodies in atopic patients and to murine anti-Der f2 monoclonal antibodies (mAbs) were examined by immunoblotting. A C-terminal deletion mutant of Der f 2, 1-123, had almost the same reactivity to human IgE as the whole Der f 2 (1-129) and an N-terminal deletion mutant of Der f 2 (25-129) still had weak reactivity. On the other hand, in two deleted Der f 2 molecules, 1-120 and 30-129, reactivity was lost in spite of long overlapping sequences. These results suggest that the human IgE antibodies to Der f 2 in atopic patient sera recognize the conformational structures dependent on the tertiary structure of Der f 2, including disulfide bond formations, rather than the contiguous sequences of amino acids. The sequences 1-24, 25-29 and 121-123 were revealed as the minimum N- and C- terminal amino acid sequences required for IgE binding. Contrastingly, all three murine mAbs bound to the smaller deletion mutants, 1-90 and 67-129, suggesting that the cores of the epitopes for these mAbs exist in the 24 amino acid sequence of Der f 2, 67-90 overlapping the sequential human IgE epitope on Der p 2, the equivalent allergen from Dermatophagoides pteronyssinus. These findings are important for the understanding of the antigenic structure of Der f 2 and for the manipulation of the allergen for immunotherapy.

Allergens↗
PubMed1997

Engineering of the major house dust mite allergen Der f 2 for allergen-specific immunotherapy.

A major problem with allergen-specific immunotherapy involving repeated injection of allergens is the risk of an anaphylactic reaction. We engineered the major house dust mite allergen, Der f 2, to reduce its capacity to induce skin test reactivity and histamine release from peripheral blood basophils in allergic patients. The engineered allergen, in which the disulfide bond that linked the N- and C-terminal sequences of Der f 2 was disrupted, retained T-cell epitopes essential for immunotherapy and ability to stimulate T-cell proliferation. Such engineered allergens are potentially useful for safer and more effective immunotherapy for allergies.

Allergens↗