Showing papers by "Fumihiko Matsuda published in 1999"

Alymphoplasia is caused by a point mutation in the mouse gene encoding Nf-κb-inducing kinase

Abstract: The alymphoplasia (aly) mutation of mouse is autosomal recessive and characterized by the systemic absence of lymph nodes (LN) and Peyer's patches (PP) and disorganized splenic and thymic structures with immunodeficiency. Although recent reports have shown that the interaction between lymphotoxin (LT) and the LT beta-receptor (Ltbeta r, encoded by Ltbr) provides a critical signal for LN genesis in mice, the aly locus on chromosome 11 is distinct from those for LT and its receptor. We found that the aly allele carries a point mutation causing an amino acid substitution in the carboxy-terminal interaction domain of Nf-kappa b-inducing kinase (Nik, encoded by the gene Nik). Transgenic complementation with wild-type Nik restored the normal structures of LN, PP, spleen and thymus, and the normal immune response in aly/aly mice. In addition, the aly mutation in a kinase domain-truncated Nik abolished its dominant-negative effect on Nf-kappa b activation induced by an excess of Ltbeta r. Our observations agree with previous reports that Ltbeta r-deficient mice showed defects in LN genesis and that Nik is a common mediator of Nf-kappa b activation by the tumour necrosis factor (TNF) receptor family. Nik is able to interact with members of the TRAF family (Traf1, 2, 3, 5 and 6), suggesting it acts downstream of TRAF-associating receptor signalling pathways, including Tnfr, Cd40, Cd30 and Ltbeta r. The phenotypes of aly/aly mice are more severe than those of Ltbr-/- mice, however, indicating involvement of Nik in signal transduction mediated by other receptors.

Fine-mapping of an ancestral recombination breakpoint in DCP1.

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Characterization of recombinant monoclonal antithyrotropin receptor antibodies (TSHRAbs) derived from lymphocytes of patients with Graves' disease: epitope and binding study of two stimulatory TSHRAbs.

Abstract: Anti-TSH receptor autoantibodies (TSHRAbs) are known to be involved in Graves' disease. To elucidate the molecular mechanism of the pathogenesis of Graves' disease, we previously isolated and reconstituted the Ig genes of two B cell clones (101-2 and B6B7) producing a monoclonal thyroid-stimulating antibody (TSAb), a stimulating type of TSHRAb, obtained from patients with Graves' disease. In the present study, we produced a large amount of recombinant monoclonal TSAbs in eukariotic cells using these genes and characterized them. First, we tried to identify their epitopes in the TSHR, by using a panel of mutants of the extracellular domain of the TSH receptor (TSHR). Substantial cell surface expression level of each mutant was confirmed by fluorescence-activated cell sorter analysis using a TSHRAb. Mutations in the N-terminal (but not C-terminal) region of the extracellular domain of TSHR abrogated or reduced TSAb activities of both antibodies, whereas they had opposite effects on TSH activity; cAMP generation by 101-2 significantly decreased in the receptors mutated in amino acids 52-56 and 58-61, and that by B6B7 decreased in amino acids 34-37 and 58-61. Secondly, purified antibodies were radiolabeled and tested for binding to cells expressing high levels of TSHR. Although their affinities were lower than that of TSH, their binding was not displaced by TSH. The antibody binding was not mutually competitive. These findings suggest that these antibodies interact with the N-terminal region of the receptor and transduce a signal through binding sites different from TSH. We believe that this is the first report of the characterization of human monoclonal TSHRAbs on their epitopes and bindings, confirming previous reports using patient sera or murine monoclonal antibodies.