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T Honjo

Publications and source records attributed to T Honjo.

At least 145 records · Page 8Linked to original sources
PubMed1996

High frequency class switching of an IgM+ B lymphoma clone CH12F3 to IgA+ cells.

We have developed an efficient in vitro class switching system using a subclone (CH12F3) of the IgM+ CH12.LX lymphoma cell line. CH12F3 cells switched from surface IgM+ cells to surface IgA+ cells at a high frequency (50%) after 72 h stimulation with IL-4, transforming growth factor (TGF)-beta and CD40L. No other class isotype-producing cells were detected, indicating that the CH12F3 clone is exclusively committed to IgA isotype switching. To understand the molecular basis of the isotype commitment, we studied the methylation profiles of I region promoters and I region transcription of CH12F3 cells. No germline transcripts other than those from the I alpha region were detected and only the I alpha promoter was demethylated in uninduced CH12F3 cells. TGF-beta, CD40L and IL-4 synergistically induced efficient switch recombination in CH12F3 cells, suggesting that the three stimulations up-regulate different steps of switch recombination in isotype-committed B cells such as CH12F3 cells. Stimulation of CH12F3 cells by IL-4 or TGF-beta, but not by CD40L, induced transient but complete methylation of the I alpha region. TGF-beta and CD40L, but not IL-4, increased the amounts of germline alpha transcripts. We found that the extents of methylation and the amounts of germline transcripts do not necessarily correlate with the efficiency of recombination in induced CH12F3 cells. These results led to the proposal that switch recombination can be separated into at least two phases, i.e. commitment and recombination. The roles of IL-4, TGF-beta and CD40L in the two phases are discussed.

Animals↗
PubMed1996

Expression of the PD-1 antigen on the surface of stimulated mouse T and B lymphocytes.

A mAb J43 has been produced against the product of the mouse PD-1 gene, a member of the Ig gene superfamily, which was previously isolated from an apoptosis-induced T cell hybridoma (2B4.11) by using subtractive hybridization. Analyses by flow cytometry and immunoprecipitation using the J43 mAb revealed that the PD-1 gene product is a 50-55 kDa membrane protein expressed on the cell surface of several PD-1 cDNA transfectants and 2B4.11 cells. Since the molecular weight calculated from the amino acid sequence is 29, 310, the PD-1 protein appears to be heavily glycosylated. Normal murine lymphoid tissues such as thymus, spleen, lymph node and bone marrow contained very small numbers of PD-1(+) cells. However, a significant PD-1(+) population appeared in the thymocytes as well as T cells in spleen and lymph nodes by the in vivo anti-CD3 mAb treatment. Furthermore, the PD-1 antigen expression was strongly induced in distinct subsets of thymocytes and spleen T cells by in vitro stimulation with either anti-CD3 mAb or concanavalin A (Con A) which could lead T cells to both activation and cell death. Similarly, PD-1 expression was induced on spleen B cells by in vitro stimulation with anti-IgM antibody. By contrast, PD-1 was not significantly expressed on lymphocytes by treatment with growth factor deprivation, dexamethasone or lipopolysaccharide. These results suggest that the expression of the PD-1 antigen is tightly regulated and induced by signal transduction through the antigen receptor and do not exclude the possibility that the PD-1 antigen may play a role in clonal selection of lymphocytes although PD-1 expression is not required for the common pathway of apoptosis.

Animals↗
PubMed1996

Developmentally regulated expression of the PD-1 protein on the surface of double-negative (CD4-CD8-) thymocytes.

PD-1, a member of the Ig superfamily, was previously isolated from an apoptosis-induced T cell hybridoma 2B4.11 by subtractive hybridization. Expresson of the PD-1 mRNA is restricted to thymus in adult mice. Using an anti-PD-1 mAb (J43), we examined expression of the PD-1 protein during differentiation of thymocytes in normal adult, fetal and RAG-2(-/-) mice with or without anti-CD3 mAb stimulation. While PD-1 was expressed only on 3-5% of total normal thymocytes, approximately 34% of the CD4(-)CD8(-) double-negative (DN) fraction are PD-1(+) cells with two distinct expression levels (low and high). PD-1(high) thymocytes belonged to TCR gammadelta lineage cells. In the DN compartment of the TCR alphabeta lineage, PD-1 expression started at the low level from the CD44(+)CD25(+) stage and the majority of thymocytes expressed PD-1 at the CD44(-)CD25(-) stage in which the thymocytes express TCR beta chains. The anti-CD3epsilon antibody administration augmented the PD-1 expression as well as the differentiation of the CD44(-)CD25(+) DN cells into the CD44(-)CD25(-) DN stage, not only in normal mice but also in RAG-2-deficient mice. The fraction of the PD-1(low) cells in the CD4(+)CD8(+) double-positive (DP) compartment was very small (<5%) but increased by stimulation with the anti-CD3 antibody, although the total number of DP cells was drastically reduced. The results show that PD-1 expression is specifically induced at the stages preceding clonal selection.

Aging↗
PubMed1996

Antigen receptor-mediated B cell death is blocked by signaling via CD72 or treatment with dextran sulfate and is defective in autoimmunity-prone mice.

Mature B cells undergo programmed cell death when surface (s) Ig is extensively multimerized. A signal that blocks death of B cells is thus required for activation of B cells in response to antigen stimulation. Here we show that only a few diverse transmembrane signals capable of inducing activation and proliferation of B cells blocked sig-mediated death of normal mature B cells, and that there is no correlation between mitogenic activity and the ability to rescue B cells from death. The results suggest that a specific signal is required for abrogating B cell death induced by sig cross-linking. Signaling via IL-4 receptor and CD40, both of which are derived from activated T cells, blocked sig-mediated death, as described previously. Signaling through a B cell antigen CD72, a counter-receptor of the pan-T antigen CD5, also blocked death of anti-Ig-treated mouse spleen B cells. CD72 signal may play a role in survival of B cells at the initial step of T-B interaction, where resting T cells recognize antigens presented by B cells. Moreover, B cell death by anti-Ig was blocked by T cell-independent antigens such as lipopolysaccharide and dextran sulfate, and spleen B cells from New Zealand mice, which are prone to autoantibody-dependent autoimmune diseases, were resistant to sig-mediated death. Mechanisms for blocking sig-mediated death may therefore be required in antibody response to foreign antigens regardless of T independence or T dependence and in autoantibody production.

Animals↗
PubMed1996

Rescue of the hairless phenotype in nude mice by transgenic insertion of the wild-type Hfh11 genomic locus.

Mice and rats homozygous for mutations at the nude (nu) locus exhibit the pleiotropic phenotypes of hairlessness and athymia. A recent positional cloning study identified, as a nude gene, a novel fork head transcription factor, Hfh11 (also called whn), that is expressed in skin and thymus, and is mutated in nude rodents. To obtain the direct biological proof that this gene is responsible for nude phenotype, we microinjected a cosmid clone containing the wild-type Hfh11 genomic locus into fertilized nude eggs. Two independent founder lines of transgenic mice were generated that corrected the hairless phenotype, but not the thymic defect. This partial rescue demonstrates that Hfh11 is the gene responsible for the hairless defect in the nude mouse. Taken together with previous genetic studies, this complementation result indicates that Hfh11 is indeed the nude gene and the Hfh11 locus is likely to be subject to complicated regulation.

Animals↗
PubMed1996

Defects of somatic hypermutation and class switching in alymphoplasia (aly) mutant mice.

The alymphoplasia (aly) mutation of mice causes the systemic absence of lymph nodes, Peyer's patches and well-defined lymphoid follicles in the spleen. We found that antibody responses are elicited, albeit weakly, to either T cell-dependent or T cell-independent antigen by aly/aly mutants. However, isotype switching was defective. The T cell-dependent immune response was not elicited in splenectomized aly/aly mice. Neither hypermutation nor germinal center formation was observed in aly/aly mice. These results suggest that T-B collaboration requires either lymph nodes or spleen, and that hypermutation and affinity maturation depend on germinal center formation.

Amino Acid Sequence↗
PubMed1995

Isolation of a novel mouse gene MA-3 that is induced upon programmed cell death.

Typical programmed cell death requires de novo macromolecular synthesis and shares common morphological changes referred to as apoptosis. To elucidate the molecular mechanism of apoptosis, we isolated cDNA clones that are induced in various types of apoptosis by the differential display method. Among such clones, the MA-3 mRNA was induced in all apoptosis-inducible cell lines tested so far, including thymocytes, T cells, B cells and pheochromocytoma. The nucleotide sequence of the MA-3 cDNA predicted an amino acid (aa) sequence of 469 aa, which did not reveal significant similarity to any known proteins and functional aa motifs in databases. The MA-3 mRNA was strongly expressed in the thymus although small amounts of the MA-3 mRNA were ubiquitously expressed in mouse adult tissues. The MA-3 gene was highly conserved during evolution and cross-hybridization bands were found not only in vertebrates but also in Drosophila melanogaster.

Amino Acid Sequence↗
PubMed1995

Physical interaction between a novel domain of the receptor Notch and the transcription factor RBP-J kappa/Su(H).

BACKGROUND: The mammalian transcription factor RBP-J kappa binds to the DNA sequence motif CGTGGGAA and is involved in the regulation of gene expression; for example, it plays a part in the transactivation of viral and cellular genes by Epstein-Barr virus nuclear antigen-2. The Drosophila homologue of RBP-J kappa is the product of the Suppressor of Hairless (Su(H)) gene. Su(H) is a neurogenic gene that acts downstream of Notch, which encodes a cell-surface receptor. Furthermore, in the mouse, the phenotypes of homozygous mutant Notch1 embryos are very similar to those of homozygous mutant RBP-J kappa embryos. Recent studies, using the yeast two-hybrid system, have led to the suggestion that the CDC10/ankyrin-like repeats of the Drosophila Notch protein interact with the Su(H) protein. RESULTS: We searched for proteins that interact with mouse RBP-J kappa using the yeast two-hybrid system, and in this way identified a short intracellular region (mRAM23) of the mouse Notch1 protein that lacks any known sequence motif. In vitro interaction studies, using proteins fused to glutathione-S-transferase, showed that RBP-J kappa and Su(H) bind directly to the RAM23 regions of mouse Notch1 and Drosophila Notch, respectively. Immunoprecipitation analysis showed that RBP-J kappa and the mRAM23 region of mouse Notch1 also interact in vivo. Further studies, including site-directed mutagenesis experiments, narrowed down the region of mouse Notch1 that interacts with RBP-J kappa. The results indicate that this region is less than 50 amino-acid residues in length, and lies immediately downstream of the transmembrane region. CONCLUSIONS: We show that the transcription factor RBP-J kappa/Su(H) interacts directly with a novel intracellular domain of the cell-surface receptor Notch. RBP-J kappa/Su(H) does not appear to interact with Notch via the CDC10/ankyrin repeats implicated in previous studies.

Amino Acid Sequence↗
PubMed1995

The murine lymphotoxin-beta receptor cDNA: isolation by the signal sequence trap and chromosomal mapping.

To isolate novel molecules involved in intercellular signaling during mouse embryogenesis, we employed the signal sequence trap (SST) method, a newly developed strategy for cloning secreted proteins and type I membrane proteins. We constructed an SST cDNA library of mouse embryonic heart mRNA, screened 2000 clones, and acquired 1 positive clone that appeared to contain the signal sequence. Homology searches revealed that this clone encodes the mouse lymphotoxin-beta receptor (LT beta-R). The deduced amino acid sequence of the mouse LT beta-R was 66% identical to that of the human LT beta-R. Northern analysis of various organs in adult mice showed that expression levels of LT beta-R mRNA were strong in lung, liver, and kidney, moderate in heart and testis, but weak in brain, thymus, spleen, and lymph nodes. Since the mouse LT beta-R was already expressed in 7-day-postcoitus embryo, the LT beta/LT beta-R system might have some functions in early embryogenesis. We performed chromosomal mapping of the murine LT beta-R gene by linkage analysis with recombinant inbred mouse strains and found that its locus is very close to the tumor necrosis factor receptor 1 gene on chromosome 6.

Amino Acid Sequence↗
PubMed1995

Structure and chromosomal localization of the human stromal cell-derived factor 1 (SDF1) gene.

Stromal cell-derived factors 1 alpha and 1 beta are small cytokines belonging to the intercrine CXC subfamily and originally isolated from a murine bone-marrow stroma cell line by the signal sequence trap method. cDNA and genomic clones of human SDF1 alpha and SDF1 beta (SDF1A and SDF1B) were isolated and characterized. cDNAs of SDF1 alpha and SDF1 beta encode proteins of 89 and 93 amino acids, respectively. SDF1 alpha and SDF1 beta sequences are more than 92% identical to those of the human counterparts. The genomic structure of the SDF1 gene revealed that human SDF1 alpha and SDF1 beta are encoded by a single gene and arise by alternative splicing. SDF1 alpha and SDF1 beta are encoded by 3 and 4 exons, respectively. Ubiquitous expression of the SDF1 gene, except in blood cells, was consistent with the presence of the GC-rich sequence in the 5'-flanking region of the SDF1 gene, as is often the case in the "housekeeping" genes. Although genes encoding other members of the intercrine family are localized on chromosome 4q or 17q, the human SDF1 gene was mapped to chromosome 10q by fluorescence in situ hybridization. Strong evolutionary conservation and unique chromosomal localization of the SDF1 gene suggest that SDF1 alpha and SDF1 beta may have important functions distinct from those of other members of the intercrine family.

Amino Acid Sequence↗
PubMed1995

Administration of interleukin-5 or -10 activates peritoneal B-1 cells and induces autoimmune hemolytic anemia in anti-erythrocyte autoantibody-transgenic mice.

Activation mechanisms of B-1 (Ly-1 B) cells have been suggested to be different from those of conventional B cells. To assess the role of various interleukins (IL) in the activation of B-1 cells, we injected IL-4, IL-5 or IL-10 into nonanemic anti-red blood cells (RBC) autoantibody-transgenic mice, in which conventional B cells are clonally deleted but peritoneal B-1 cells persist without secreting Ig. Intraperitoneal or intramuscular injection of IL-5 or IL-10, but not IL-4, increased the number of antibody-producing peritoneal B-1 cells by four- to five-fold, resulting in increased anti-RBC serum autoantibody and induction of hemolytic anemia. These results suggest that IL-5 or IL-10 may play an important role in the terminal differentiation of B-1 cells into antibody-producing cells in vivo.

Anemia, Hemolytic, Autoimmune↗
PubMed1995

Involvement of B-1 cells in mucosal immunity and autoimmunity.

B-1 cells are distinguished from conventional B cells by their anatomical localization, surface phenotypes and functional characteristics. The physiological functions and pathological roles of these cells remain controversial. In this review, Masao Murakami and Tasuku Honjo summarize recent evidence for the involvement of B-1 cells in mucosal immunity and autoimmunity, and discuss the relationship between these phenomena.

Animals↗
PubMed1995

Prevention of autoimmune symptoms in autoimmune-prone mice by elimination of B-1 cells.

Our recent studies on an autoantibody-transgenic mouse line demonstrated that peritoneal B-1 cells are responsible for autoimmune symptoms. However, whether B-1 cells in the peritoneum are generally involved in the pathogenesis of autoimmune disease remains controversial. To test the possible involvement of peritoneal B-1 cells in autoimmune symptoms of autoimmune-prone NZB mice, we eliminated the peritoneal cells by hypotonic shock with repeated i.p. injection of distilled water every 7 days into neonatal or 8-week-old NZB mice. By this treatment, B-1 cells, which self-renew within the peritoneal cavity, are expected to be preferentially eliminated, while other peritoneal cells can be easily supplied from bone marrows after this treatment. Indeed, in distilled water-treated old NZB mice, the number of B-1 cells decreased in spleen as well as in lamina propria of the gut but the numbers of conventional B cells and T cells did not change. Moreover, the production of autoantibodies against erythrocytes significantly decreased and the occurrence of autoimmune hemolytic anemia was reduced in 12-month-old treated NZB mice. Similarly, the elimination of peritoneal cells of NZB/NZW (NZB/W) F1 mice by water injection decreased anti-DNA IgG antibodies in the sera and reduced the pathological changes of the kidney. These results suggest that peritoneal B-1 cells may be a source of autoantibody-producing cells in autoimmune diseases of NZB and NZB/W F1 mice.

Anemia, Hemolytic, Autoimmune↗
PubMed1995

Loss of immunostaining of the RBP-J kappa transcription factor upon F9 cell differentiation induced by retinoic acid.

RBP-Jkappa is a novel type of transcriptional regulatory protein that does not contain any known DNA-binding motif. We raised anti-RBP-Jkappa monoclonal antibodies (K0043 and T6709) to investigate the roles of RBP-Jkappa in cell differentiation. These antibodies stained nuclei of undifferentiated embryonic stem cells and F9 cells but not those of the other differentiated cell lines tested so far although the RBP-Jkappa protein is expressed at similar levels. Interestingly, differentiated F9 cells lost the immunostaining reaction with the anti-RBP-Jkappa monoclonal antibodies. Biochemical subcellular fractionation study showed that the majority of RBP-Jkappa was localized in nuclei of F9 cells and that there are at least two forms of the RBP-Jkapppa protein in the nuclei of undifferentiated F9 cells, a free form and a chromatin-bound form. Upon induction of F9 cell differentiation, free nuclear RBP-Jkappa disappeared concomitantly with the loss of immunostaining, suggesting that the anti-RBP-Jkapppa antibodies cannot recognize chromatin-bound RBP-Jkappa. Since there is no evidence to indicate covalent modification of RBP-Jkappa, we assume that chromatin-bound RBP-Jkappa interacts with a large number of proteins which block the exposure of RBP-Jkappa epitopes to the monoclonal antibodies.

3T3 Cells↗
PubMed1995

Disruption of the mouse RBP-J kappa gene results in early embryonic death.

The RBP-J kappa protein is a transcription factor that recognizes the sequence C(T)GTGGGGA. The RBP-J kappa gene is highly conserved in a wide variety of species and the Drosophila homologue has been shown to be identical to Suppressor of Hairless [Su(H)] which plays important roles in the development of the peripheral nervous system. To explore the function of the RBP-J kappa gene in mouse embryogenesis, a mutation was introduced into the functional RBP-J kappa gene in embryonic stem (ES) cells by homologous recombination. Null mutant ES cells survived but null mutant mice showed embryonic lethality before 10.5 days of gestation. The mutant mice showed severe growth retardation as early as 8.5 days of gestation. Developmental abnormalities, including incomplete turning of the body axis, microencephaly, abnormal placental development, anterior neuropore opening and defective somitogenesis, were observed in the mutant mice at 9.5 days of gestation. RBP-J kappa mutant embryos expressed a posterior mesodermal marker FGFR1. Their irregularly shaped somites expressed a somite marker gene Mox 1 but failed to express myogenin. The RBP-J kappa gene was revealed to be essential for postimplantation development of mice.

Animals↗
PubMed1995

Suppressor of hairless, the Drosophila homologue of RBP-J kappa, transactivates the neurogenic gene E(spl)m8.

Suppressor of Hairless[Su(H)], the Drosophila homologue of RBP-J kappa is a novel type of sequence-specific DNA binding protein without known motifs, and highly conserved in various organisms. Su(H) regulates peripheral nervous system (PNS) development. Recently Su(H) was suggested to participate in the Notch-mediated signal transduction pathway. We show here that the Su(H) protein binds to TGTGGGAA sequence located 616 base-pairs upstream of the transcription initiation site of the Enhancer of split [E(spl)]m8 gene which is mapped to the terminus of the genetic cascade of the neurogenic genes. Su(H) transactivates the E(spl)m8 promoter not only in cultured Drosophila cells but also in vivo. The present study bridges the biochemical gap between Notch and E(spl) in the neurogenic gene cascade including Delta, Notch, deltex, Su(H), Hairless and E(spl).

Alleles↗