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T Honjo

Publications and source records attributed to T Honjo.

At least 325 records · Page 18Linked to original sources
PubMed1986

Molecular basis for two different affinity states of the interleukin 2 receptor: affinity conversion model.

Two affinity species of the interleukin 2 (IL-2) receptor are different states of a single receptor molecule. We assumed that a binary complex between the IL-2 receptor and another lymphocyte-specific protein would constitute the high-affinity receptor. To test this assumption, we counted the numbers of IL-2 receptors with high and low affinity in a murine T-cell line CT/hR-1 that expresses not only murine but also human receptors by cDNA transfection. We found that human high-affinity receptors disappeared when the murine high-affinity receptors were already occupied by the ligand. The results were incompatible with a fixed number of human and murine receptors with high affinity in CT/hR-1 cells. We suggest that the high-affinity state of the IL-2 receptor is a ternary complex of IL-2, the IL-2 receptor, and a postulated "converter" protein, which is fewer in number than the receptors. The converter would be unable to form a complex with the IL-2 receptor unless IL-2 was already bound to it. The ligand binding to the receptor would cause a conformational change in the receptor, increasing its affinity to the converter. Ternary complex formation would, in turn, change the apparent affinity of the receptor to the ligand from low to high by reduction of the dissociation constant.

Allosteric Regulation↗
PubMed1986

Structure and function of the interleukin 2 receptor: affinity conversion model.

We cloned cDNAs of the human and mouse IL-2 receptors. Comparison of their structures allowed us to identify several conserved regions localized to exons 2 and 4, the cytoplasmic portion and the transmembrane portion. These regions might be important for the functions of the IL-2 receptor. The human IL-2 receptor, which was expressed on an IL-2-dependent murine T-cell line, CTLL-2, by cDNA transfection, was shown to be functionally active by blocking the endogenous mouse IL-2 receptor with monoclonal antibodies. On the other hand, the human IL-2 receptors expressed on non-lymphoid cells were functionally inactive. They were unable to mediate the growth signal, were of low affinity species and aberrant in internalization. We postulated that the dysfunction of the IL-2 receptors in non-lymphoid cells would be due to the absence of the putative converter protein which is expressed specifically in lymphoid cells. Since the human IL-2 receptor is active in the murine T cell, the converter may interact with the receptor at the portions conserved between man and mouse. We proposed the affinity conversion model that explained the high affinity state of the receptor by the ternary complex formation between IL-2, the IL-2 receptor and the converter.

Allosteric Regulation↗
PubMed1986

Cytochemical, immunologic, chromosomal, and molecular genetic analysis of a novel cell line derived from Hodgkin's disease.

A novel cell line, KM-H2, was established from the pleural effusion of a patient with Hodgkin's disease of mixed cellular type. Multiple phenotypic studies were carried out with this cell line. Acid phosphatase and nonspecific esterase activities were detected. Rosette formation with T lymphocytes and the receptors for C3b and Fc portion of IgG were positive. Among the antigens tested with a total of 22 monoclonal antibodies defining hematopoietic cell subsets or lineages, Ki-1, Leu-M1, MCS1, HLA-DR, and OKT9 antigens were found to be positive. The other antigens reportedly specific for T cells, B cells, natural killer (NK) cells, monocytes, interdigitating reticulum (IR) cells and dendritic reticulum cells were negative. These phenotypic features were identical to those of the Sternberg-Reed (SR) and Hodgkin (H) cells in the fresh materials reported by other researchers. Moreover, the KM-H2 cells and the parental pleural effusion cells shared several structural chromosome anomalies. These findings indicated that the KM-H2 cells are derived from the SR and H cells. Molecular genetic analysis of the KM-H2 cells disclosed that the human immunoglobulin JH gene was rearranged but not the JK gene, and that the human T cell receptor beta chain gene was of the germline type. Based on these properties of the KM-H2 cells, Hodgkin's disease may be derived from a cell lineage other than T cell or B cell.

Adult↗
PubMed1986

[Molecular genetic studies on the immune system: an approach to a clinical application].

It is the function of the immune system to recognize and neutralize numerous antigens invading animals. The more diverse the antigen recognition of the organism, the more efficient is its defense system. There are two types of antigen recognition molecules in the immune system; the immunoglobulin produced by B cells and the T cell antigen receptor. These molecules have variable (V) regions which recognize antigens and constant (C) regions which mediate physiological functions. The latter provide additional diversity to the immune system. For example, the same heavy chain (H) V regions recognizing influenza hemagglutinin are expressed as the mu, gamma, epsilon, and a chains, each of which constitutes a different class of the immunoglobulin. Since the V and C regions are encoded by separate sets of DNA segments, it is the genetic variability of the V gene that determines the antigen recognition diversity. Recent molecular genetic studies on the immunoglobulin gene and the T cell antigen receptor gene indicate that the V region genes of both molecules produce somatic as well as evolutionary variations. Somatic variations include joining of two or three germ-line segments by site-specific recombinations and somatic base replacements. Evolutionary variations include gene duplication, segment transfer (gene conversion), mutational drifts, and so on. Since genetic events, be it somatic or evolutionary, tend to be random, not only useful but also harmful immunoglobulins are produced. Therefore, appropriate selection, be it positive or negative, is a prerequisite for the proper function of the genetic diversity of the immune system as the defense mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Production and characterization of the extracytoplasmic portion of the human interleukin-2 receptor.

We made a mutant cDNA clone of the human interleukin-2 (IL-2) receptor by introducing a termination codon at the eighth amino acid residue upstream from the putative transmembrane region. Ltk- cells were transfected by this mutant cDNA and cell-lines secreting the extracytoplasmic portion of the IL-2 receptor were established. The artificial secretory molecule of the IL-2 receptor named "bottom-less" receptor was able to react with anti-Tac antibody and to bind IL-2. We purified the bottom-less receptor to homogeneity by affinity chromatography using an IL-2-Sepharose column. The affinity (Kd value) of the 125I-labeled bottom-less receptor to IL-2 coupled to Sepharose beads was estimated to be 4.5 microM. All these results confirm the putative membrane topology of the IL-2 receptor based on the primary structure, and suggest that the bottom-less receptor may maintain the basic structure and function of the extracytoplasmic portion of the IL-2 receptor.

Cell Line↗
PubMed1985

Origin of human T-lymphotrophic virus I-positive T cell lines in adult T cell leukemia. Analysis of T cell receptor gene rearrangement.

Using the clone-specific rearrangement of the T cell receptor gene as the genetic marker of the clonotype, we analyzed the clonal origin of the interleukin 2 (IL-2)-dependent human T-lymphotrophic virus I (HTLV-I)-positive T cell lines established from various adult T cell leukemia (ATL) patients. From a patient with chronic ATL, whose leukemic cells proliferated in vitro in response to IL-2, we repeatedly established leukemic T cell clones having the same rearrangement profile of the T beta chain gene as the leukemic cells. By contrast, established cell lines from acute ATL patients had different beta chain gene rearrangements from those of the leukemic cells. These HTLV-I+ T cell lines might not be the direct progeny of the leukemic cells, but that of T cells infected either in vivo or in vitro. These IL-2-reactive nonleukemic T cells might have been selected in vitro, because their leukemic cells failed to respond to IL-2, despite the expression of IL-2 receptor. The analysis of the T cell receptor gene rearrangement may give a new approach for the elucidation of the mechanism of leukemogenesis and the origin of the HTLV-I+ T cell lines in ATL.

Acute Disease↗
PubMed1985

Molecular cloning and structure of the human interleukin 2 receptor gene.

We have cloned the IL-2 receptor gene from human genomic DNA libraries using IL-2 receptor cDNA as probe. The genomic DNA segments that hybridized with cDNA were subcloned in M13 phages and their sequences were determined. The nucleotide sequences showed that the IL-2 receptor gene was encoded by eight exons and that the coding region sequences agreed completely with that of the IL-2 receptor cDNA cloned from a cell line derived from adult T cell leukemia (ATL), in which IL-2 receptors are expressed abnormally. The nucleotide sequence of the 5'-flanking region had a putative promotor region, which had some homology with the human IL-2 gene. Transcription initiation sites were clustered about 25 bp 3' to the TATA box as assessed by primer extension analysis. These sites for normal and ATL T cells were the same. Exons 2 and 4 encoding the extracytoplasmic portion had significant homology, suggesting that the two exons are derived by duplication of an ancestral exon. Exon 2 contained six cysteine residues, four of which are conserved at the corresponding positions in exon 4.

Amino Acid Sequence↗
PubMed1985

Rat lymphoid cell lines producing human T cell leukemia virus. II. Constitutive expression of rat interleukin 2 receptor.

Three rat lymphoid cell lines (TARS-1, TARL-2, and TART-1) (12) transformed by human T cell leukemia/lymphoma virus I (HTLV-I) had rearrangement of the beta chain gene of the T cell antigen receptor, and had integrated proviral DNA from HTLV-I in their genomes. As is the case with adult T cell leukemia (ATL)-derived human T cell lines transformed by HTLV-I, these rat cell lines unequivocally expressed interleukin 2 (IL-2) receptor, as determined by radiolabeled IL-2 binding. By Scatchard plot analysis, one of the cell lines, TART-1, proved to have high affinity receptors (Ka = 1.3 X 10(11)/M and 8.8 X 10(9)/M). Rat IL-2 receptor, not human IL-2 receptor, was expressed on HTLV+ rat cell lines, as demonstrated by the fact that they expressed antigens reactive with monoclonal antibodies (ART-18) against rat IL-2 receptor, but not with anti-Tac antibodies. The collective evidence indicates that the endogenous IL-2 receptor gene is activated in human and rat lymphoid cell lines with HTLV-I production. The mechanism of abnormal IL-2 receptor expression in HTLV infection is discussed.

Animals↗
PubMed1985

Nucleotide sequence of mouse IL-2 receptor cDNA and its comparison with the human IL-2 receptor sequence.

We have cloned cDNA encoding the mouse interleukin-2 (IL-2) receptor from a murine T cell line, CTLL using human IL-2 receptor cDNA as probe. COS 7 cells transfected with the cDNA expressed the antigen recognized by the monoclonal antibody against the murine IL-2 receptor. The cDNA identified 4 species of mRNA (4.5, 3.5, 2.2 and 1.5 kb) of the mouse IL-2 receptor in CTLL cells. Difference in the length of mRNA seems to be ascribed to the variable length of the 3' untranslated sequence. Total nucleotide sequence (approximately 1400 bp) of this cDNA was determined and compared with the human receptor. The nucleotide and amino acid sequences of the IL-2 receptor are 70% and 60%, respectively, homologous in average between the two species. The comparison has revealed several conserved regions localized to particular exons such as transmembrane and cytoplasmic portions, suggesting that these regions are important for receptor function and its regulation.

Amino Acid Sequence↗
PubMed1985

IgE heavy chain constant region genes in atopic dermatitis and senile erythroderma patients.

By Southern hybridization using a genomic DNA fragment carrying a human IgE heavy chain constant region gene (C epsilon) as a probe, we analyzed the organization of human C epsilon genes and their flanking regions in 23 atopic dermatitis and 6 senile erythroderma patients with elevated serum IgE levels, and 6 atopic dermatitis patients with normal IgE levels. On Bam HI, Hind III, and Eco RI digestions, we detected three hybridizable fragments containing three human C epsilon genes, C epsilon 1, C epsilon 2, and C epsilon 3, respectively, in all leukocyte DNAs. These fragments were almost identical in size among patients and healthy donors. Pst I digestion generated a genetic polymorphism. We, however, could find no correlation between this polymorphism and the disorders. It was concluded that among the patients and healthy donors, there was no marked difference in the organization of the functional C epsilon gene and its flanking region containing a class switch region. Our conclusion cannot rule out the presence of genetic abnormalities of this region in some atopic dermatitis patients which are not resolvable by our method. In the course of this study, we found a novel C epsilon-like gene in placenta DNA which differs from the three C epsilon genes commonly present in normal human DNA.

Adult↗
PubMed1985

Absence of gross change in primary DNA sequence during aging process of mice.

The possibility of age-associated changes in DNA sequence in terms of amplification and rearrangement was examined in mouse spleen, liver and brain using the method of Southern transfer and filter hybridization. The DNA regions studied were at and around nine cloned sequences, most of which are known to move or amplify in certain situations. No detectable age-associated change, however, was observed in all DNA regions studied. These results suggest that widespread DNA sequence rearrangements or amplifications do not occur during the ageing process in mice.

Aging↗
PubMed1985

A truncated immunoglobulin epsilon pseudogene is found in gorilla and man but not in chimpanzee.

Molecular genetic analyses of the young pseudogenes of the immunoglobulin C epsilon genes were carried out to obtain qualitative evidence for the phylogenetic branching pattern of hominoid primates. We found that Old World monkeys had two C epsilon genes, one of which was processed. Among the hominoids examined only the gorilla and human genomes contained three C epsilon genes: an active, a truncated, and a processed gene. Other hominoids so far examined, including chimpanzee, contained two C epsilon genes: one active and the other processed. These results suggest that the processed C epsilon pseudogene was generated before the divergence between Old World monkeys and hominoids and that the gorilla is more closely related to man than the chimpanzee is, unless the chimpanzee has lost the C epsilon 2 gene after the divergence of this species.

Animals↗
PubMed1985

Structures of defective P transposable elements prevalent in natural Q and Q-derived M strains of Drosophila melanogaster.

Several DNA sequences with homology to the complete 2.9-kilobase (kb) P element from a P strain in the United States were isolated and characterized from two Drosophila melanogaster strains collected on Chichi Jima, an island 1000 km south of Tokyo. Except for a missing central region and trivial unsequenced regions of 38 base pairs, the 2.1-kb element isolated from a Q strain had the same DNA sequence as that of the complete P element. Seven other elements cloned from genomic DNAs of the Q strain and a Q-derived M strain all possessed the same restriction sites as those of the 2.9-kb P element except for one deleted region in each element. The finding of sequence conservation in P elements have had a common ancestor relatively recently. Thus, it is suggested that the P element family was a recent invader of the species. By contrast, no complete P element was found in these Japanese strains so far as surveyed, indicating the possibility that P elements in the Chichi Jima population are almost all defective. The implication of this possibility is discussed in relation to the uniqueness of the population on Chichi Jima where Q strains predominate and no P strains have yet been found.

Journal Article↗