Biomedical subjects

C Morimoto

Publications and source records attributed to C Morimoto.

At least 109 records · Page 6Linked to original sources

PubMed1995

A novel form of dipeptidylpeptidase IV found in human serum. Isolation, characterization, and comparison with T lymphocyte membrane dipeptidylpeptidase IV (CD26).

Human CD26, a Type II membrane glycoprotein with intrinsic dipeptidylpeptidase IV (DPPIV) activity and ability to bind adenosine deaminase type I (ADA-1), is expressed on epithelial cells constitutively, but on T lymphocytes its expression is regulated. A soluble form of CD26/DPPIV has been described in plasma and related to immunological status, but it has been defined by the presence of DPPIV activity rather than by isolation. Using nondenaturing chromatographic techniques followed by nondenaturing native preparative electrophoresis, we obtained a homogeneous preparation of soluble serum DPPIV and compared it with a recombinant soluble CD26/DPPIV (rsCD26). We show that serum DPPIV is a monomer of 175 kDa in contrast to rsCD26 of 105-110 kDa, that it exists as a trimer, and that it is probably a serine proteinase. Deglycosylation removed N-linked sugar from both serum DPPIV and rsCD26; no O-linked glycosylation was observed, revealing a protein core of 130 kDa for serum DPPIV. The large serum form expresses functional DPPIV activity with substrate and inhibitor specificities and pH activity profile similar to those of rsCD26. Epitope analysis showed that monoclonal antibodies against five epitopes expressed by rsCD26 also bound, but more weakly, with serum DPPIV. Analysis of peptides after limiting proteolysis and N-terminal sequences reveals no homology with rsCD26 but some identity with other peptidases. Unlike rsCD26, the serum form does not bind ADA-1 and has no ADA-1 already associated with it. Similarly to rsCD26, serum DPPIV is a potent T cell costimulator. We conclude that the serum form of DPPIV is unique and is not a breakdown product of membrane CD26. The conservation of DPPIV activity and five epitopes specific to rsCD26 suggest, however, a significant structural similarity.

Adenosine Deaminase↗

PubMed1995

Direct cellular communications between CD45R0 and CD45RA T cell subsets via CD27/CD70.

The engagement of CD27 with its ligand CD70 is considered to play an important role in T cell costimulation. In the present study, we investigated both the kinetics of CD70 expression and the contribution of its interaction with CD27 in T cell immune responses. CD70 was found to be expressed almost equally on both activated CD4 and CD8 T cells. On subsets of CD4 T cells, however, CD70 expression was induced preferentially on the CD45R0 T cell population after activation, whereas its expression was not noted on CD45RA T cells for almost 2 wk following activation. In long-term culture with media containing T cell growth factor (TCGF) and rIL-2, the expression of CD70 was increased markedly on CD45R0 T cells and minimally expressed on CD45RA T cells. In addition, strong surface expression of CD70 was observed on T cell clones originally derived from CD45R0+ CD4 T cells, whereas T cell clones originally derived from CD45RA+ CD4 T cells showed lower levels of expression. The addition of irradiated, activated CD45R0 T cells to CD45RA T cells caused a down-regulation of CD27 expression and an up-regulation of CD25 expression. These changes were blocked by addition of the anti-CD70 mAb, suggesting that direct contact between CD45R0 T cells and CD45RA T cells via CD27/CD70 occurred, leading to the activation of CD45RA T cells as measured by CD25 expression. These observations strongly support the notion that the engagement of CD27 plays an important regulatory role in the communication of subsets of CD45R0 and CD45RA T cells.

Antigens, CD↗

PubMed1995

Differential CD26-mediated activation of the CD3 and CD2 pathways after CD6-depleted allogeneic bone marrow transplantation.

Patients who have undergone allogeneic bone marrow transplantation (allo-BMT) are susceptible to a variety of opportunistic infectious complications in the months to years after engraftment. Impaired in vitro T-cell functions have been documented in these patients, and these T-cell dysfunctions contribute to the prolonged immune deficiency after allo-BMT. In the present study, we examined the expression of CD26 as well as the reconstitution of CD26-mediated T-cell costimulation via the CD3 and CD2 pathways at various times in patients aged greater than 18 years after CD6-positive, T-cell depleted allo-BMT. We found that the percentage of CD26- and CD3-positive cells, as well as the levels of expression of both antigens, was lower than in normal controls during the first 4 months after CD6-depleted allo-BMT. Subsequently, the amount of lymphocytes expressing CD3 and CD26 and the quantitative surface expression of CD3 and CD26 were not significantly different in patients and normal controls. Functional studies showed that CD26-mediated T-cell proliferation via the CD3 pathway was considerably improved and almost reached normal levels by 1 year, whereas recovery of CD26-mediated T-cell proliferation via the CD2 pathway was delayed for at least 2 years after CD6-depleted allo-BMT. As CD26 involvement in the regulation of human thymocyte activation is restricted preferentially to the CD3 pathway--unlike its involvement with both CD3 and CD2 pathways of peripheral T cells--our results suggest that the different effects of CD26-mediated costimulation via the CD3 and CD2 pathways after CD6-depleted allo-BMT may be a reflection of peripheral T-cell immaturity in those individuals, similar to that seen in mature medullary thymocytes or cord T lymphocytes.

Adolescent↗

PubMed1995

Comparison of lymphokine secretion and mRNA expression in the CD45RA+ and CD45RO+ subsets of human peripheral blood CD4+ and CD8+ lymphocytes.

Flow cytometric analysis of human peripheral blood T lymphocytes demonstrated that the majority of the CD4+ cells were CD29+ or CD45RO+ "mature" cells while the CD8+ cells were primarily CD45RA+ "native" cells. After an initial separation into CD4+ and CD8+ cells and a secondary separation into CD45 subsets, lymphokine secretion was assessed after phorbol 12-myristate 13-acetate and ionomycin or fixed anti-CD3 stimulation. Within the respective CD45 subsets, CD4+ cells produced more interleukin (IL)-2, IL-4, and IL-6; but the CD8+ cells secreted more interferon-gamma and granulocyte/macrophage-colony-stimulating factor. Tumor necrosis factor-alpha secretion was similar in the matched CD45 subsets. Northern analysis revealed a parallel pattern of lymphokine mRNA expression in the four lymphocyte subsets. These results suggest that human CD8+ peripheral blood lymphocytes have a significant capacity to secrete lymphokines, and that the low lymphokine production observed in unseparated CD8+ cells reflects the higher percentage of less functional CD45RA+ cells.

CD3 Complex↗

PubMed1995

CD8+ and CD45RA+ human peripheral blood lymphocytes are potent sources of macrophage inflammatory protein 1 alpha, interleukin-8 and RANTES.

The chemokines macrophage inflammatory protein 1 alpha (MIP 1 alpha), interleukin-8 (IL-8) and RANTES are potent regulators of leukocyte trafficking. Examination of chemokine secretion by human peripheral blood lymphocytes after stimulation with anti-CD3 or phorbol 12, 13 myristate acetate and ionomycin showed CD8+ cells were the dominant source of MIP 1 alpha and RANTES. Although production of MIP 1 alpha and IL-8 were similar in pharmacologically stimulated CD4+ CD45RA+, CD4+ CD45RO+, and CD8+ CD45RA+ cells, the largest amounts of MIP 1 alpha and RANTES were secreted by CD8+ CD45RO+ lymphocytes. A parallel pattern of prolonged chemokine mRNA expression for at least 18 h after activation was observed in the T cells subsets. These results confirm that human T lymphocytes have a unique capacity for secretion of these three chemokines. In addition, CD8+ cells have an unrecognized role in recruiting cells to sites of inflammation, and adult human CD45RA+ cells have a physiologically significant secretory capacity.

Blotting, Northern↗

PubMed1995

CD27/CD70 interaction directly drives B cell IgG and IgM synthesis.

CD27 is a T cell activation antigen expressed on a majority of peripheral blood T cells. CD27 is also expressed on a subpopulation of human B cells, and it is reported that CD27+ B cells secrete both IgG and IgM. CD70, a ligand for CD27, is expressed on activated T and B cells, suggesting an interaction between T and B cells via CD27/CD70 ligation. Here, we analyze B cell immunoglobulin synthesis using a CD70 transfectant and present functional data showing that B cells secrete large amounts of IgG and IgM as a result of the CD27/CD70 interaction. A flow cytometric analysis showed that CD27 expression was increased and CD70 was expressed on tonsillar and peripheral blood B cells after activation with Staphylococcus aureus Cowan strain (SAC) plus interleukin (IL-2). In addition, the proliferation of B cells was enhanced mildly by the addition of CD70 transfectant, and its proliferation was blocked by anti-CD70 mAb. More importantly, the CD70 transfectant enhanced IgG and IgM production by purified B cells greatly in the presence of SAC plus IL-2. The enhancement was completely blocked by the addition of either anti-CD70 mAb or anti-CD27 mAb. Strongly suggesting that the interaction of CD27 with its ligand, CD70, on B cells plays an important role in B cell growth and differentiation to produce IgG and IgM.

Adult↗

PubMed1995

Mechanism of increase in basal lipolysis of enlarged adipocytes in obese animals.

Sonication of rat fat cells caused an increase in lipolysis in the absence of lipolytic hormones (basal lipolysis) and loss of epinephrine responsiveness. Sonication of endogenous lipid droplets from fat cells also induced an increase in lipolysis in the presence of HSL. Addition of phosphatidylcholine to the sonicated lipid droplets reduced the hydrolysis of triglyceride by HSL. These results suggest that the active HSL is already present in the fat cell even in the absence of lipolytic hormone, and phosphatidylcholine on the surface of endogenous lipid droplets causes inhibition toward lipolytic action of HSL. The decrease in the surface phosphatidylcholine concentration in endogenous lipid droplets was proved to cause the increase in basal lipolysis. It is demonstrated that basal lipolysis was elevated in the enlarged fat cells of obese rats by reduction of surface phosphatidylcholine concentration of the endogenous lipid droplets.

Adipocytes↗

PubMed1995

Focal adhesion kinase (pp125FAK) is tyrosine phosphorylated after engagement of alpha 4 beta 1 and alpha 5 beta 1 integrins on human T-lymphoblastic cells.

pp125FAK is a novel protein tyrosine kinase associated with focal adhesions. It has been shown that ligation of VLA beta 1 integrins on a number of cell types enhanced tyrosine phosphorylation and kinase activity of pp125FAK. Cellular transformation by retroviral oncogene products or mitogenic neuropeptides also result in the activation of this kinase. On the basis of these observations, pp125FAK has been proposed to be a key regulatory molecule connecting cell adhesion, transformation, and growth. We have previously shown that ligation of VLA beta 1 integrins induced CD3-dependent T cell proliferation and stimulated tyrosine phosphorylation of a molecular mass with a 105-kDa protein (pp105). Here we report that engagement of alpha 4 beta 1 and alpha 5 beta 1 integrins by adherence to their respective ligands stimulated tyrosine phosphorylation of 105- to 120-kDa proteins (pp105 and pp120, respectively) in human H9 T-lymphoblastic cells. At least one component of the 105- to 120-kDa proteins was found to be tyrosine-phosphorylated pp125FAK. While kinetics of adherence-dependent tyrosine phosphorylation of pp120/pp125FAK and pp105 are closely similar, pp105 appeared to be distinct from pp125FAK. Given T cell costimulation induced by VLA beta 1 integrins and the putative functional role of pp125FAK in cell growth, tyrosine phosphorylation of these two distinct proteins may be involved in T cell activation and proliferation.

Cell Adhesion↗

PubMed1994

CD27 is a signal-transducing molecule involved in CD45RA+ naive T cell costimulation.

CD27 is a 120-kDa transmembrane homodimeric molecule expressed on the majority of T cells, B cells, and NK cells that belongs to the TNFR/nerve growth factor receptor family. The interaction between CD27 and its ligand, CD70, is thought to play an important role in T cell activation. In this paper we have examined the signal-transducing potential of CD27 in T cell costimulation. Anti-CD27 mAb, anti-1A4, induced substantial proliferation of peripheral blood T cells in the presence of a suboptimal dose of PMA, phytohemagglutinin, anti-CD2, or anti-CD3 together with a second Ab to cross-link the CD27 molecule. This T cell proliferation was also observed by using CD70 transfectant cells. CD27 cross-linking maximally induced proliferation of CD45RA+CD4 T cells but only slightly induced proliferation of CD45RO+CD4 T cells. CD27-mediated T cell proliferation did not seem to be dependent on the IL-2/IL-2R system because no detectable level of IL-2 was secreted, and only a partial inhibition was observed with anti-IL-2 and anti-IL-2R Abs. Furthermore, an increase in intracellular Ca2+ was observed in PMA-treated T cells when the CD27 molecule was cross-linked. More importantly, CD27 ligation induced protein tyrosine phosphorylation, especially 70 kDa of cellular substrate, including ZAP-70, in T cells. Herbimycin A, a protein tyrosine kinase inhibitor, and staurosporine, a protein kinase C inhibitor, blocked T cell proliferation induced by CD27 ligation, suggesting the possibility that the activation of protein tyrosine kinase and protein kinase C is required for CD27-mediated T cell costimulation. These results clearly demonstrate that the CD27/CD70 interaction induces costimulatory signals in T cells, especially CD45RA+ naive T cells, indicating that CD27 serves as a T cell signal-transducing molecule.

Base Sequence↗

PubMed1994

Differential regulation of CD27 expression on subsets of CD4 T cells.

Our earlier studies showed that although CD27 was stably expressed on the CD45RA(+)-CD45RO-CD29low subset of CD4 T cells, its expression on the CD45RA-CD45RO+CD29high subset of CD4 T cells was gradually lost within 3 weeks after PHA activation. In the present study, we further determined the mechanisms by which the CD27 expression was differentially regulated on the subsets of CD4 T cells. We showed that disappearance of CD27 from the surface of the CD45RA-CD45RO+ subset of CD4 T cells was not solely due to the shedding of the CD27 molecule from the cell surface since the release of a soluble form of the CD27 molecule from the CD45RO+ CD4 T cells was consistently less than that from CD45RA+ CD4 T cells. Although the surface CD27 expression was undetectable on long-term cultured T cell lines originally derived from CD45RO+ CD4 T cells, some of these cells still expressed intracellular CD27 and CD27 mRNA. Moreover, restimulation could not induce CD27 expression on such cells. Further analysis of CD27 protein and mRNA expression at a clonal level showed that cloned cells derived from CD45RO+ CD4 T cells having lost cell surface expression of CD27 were of two types: one expressed intracellular CD27 mRNA and protein whereas the second lacked both intracellular CD27 mRNA and protein.

Blotting, Northern↗

PubMed1994

Role of CD26/dipeptidyl peptidase IV in human immunodeficiency virus type 1 infection and apoptosis.

To examine the role of CD26/dipeptidyl peptidase IV (DPPIV; EC 3.4.14.5) in infection by human immunodeficiency virus type 1 (HIV-1), we utilized CD26 cDNA-transfected Jurkat T-cell lines. Both CD26- parental Jurkat cells and mutant CD26+ (DPPIV-) transfected Jurkat cells were readily infected with HIV-1, whereas wild-type CD26+ (DPPIV+) transfected Jurkat cells were more resistant to HIV-1 infection. Our results suggest that CD26 is not essential for HIV-1 infectivity as suggested by others but that DPPIV enzyme activity may decrease the efficiency of HIV-1 infection. Of great interest, we found that mutant CD26+ (DPPIV-) transfectants and CD26- parental Jurkat cells strongly expressed CD95 (Fas/Apo-1) and were more sensitive than wild-type CD26+ (DPPIV+) transfectants to the induction of apoptosis by anti-CD95 monoclonal antibody. These results suggest that CD26 may play a role in HIV-1-associated loss of -CD4+ cells through the process of programmed cell death.

Antigens, CD↗

PubMed1994

Role of CD27 in T cell immune response. Analysis by recombinant soluble CD27.

CD27 is a disulfide-linked 120-kDa transmembrane glycoprotein expressed on the majority of T cells, B cells, and NK cells; it has homology to a family of molecules that includes the receptors for nerve growth factor and TNF. Previous studies strongly suggest that the CD27 molecule plays a key role in the process of T cell activation. To further determine its role in T cell activation, a recombinant soluble molecule composing only the extracellular domain of CD27 was produced by transfection of Chinese hamster ovary cells. We have defined the binding properties of recombinant soluble CD27 (rsCD27) to CD27 ligand (CD27L) cDNA transfected NIH 3T3 cells and have determined its functional effects on in vitro T cell activation as well as on PWM-driven B cell IgG synthesis. rsCD27 bound specifically to CD27L and the binding was inhibited by one of our anti-CD27 mAbs, anti-1A4, suggesting that the 1A4 epitope of CD27 plays a role in the binding to CD27L. Functionally, rsCD27 inhibited T cell proliferation induced by various stimuli, such as PHA, tetanus toxoid, and anti-CD2, as well as PWM-driven B cell IgG synthesis, similar to the effects of adding anti-1A4. Determination of CD27L expression showed that CD27L mRNA is induced rapidly on activated T and B cells. Taken together, these results provide direct evidence that CD27-CD27L interaction plays a critical role in T cell activation as well as in T cell-dependent B cell IgG synthesis, suggesting that the CD27-CD27L interaction may constitute a component of the T cell-T cell or T cell-B cell interaction seen after activation with Ag or mitogen.

Antibody Formation↗

PubMed1994

The phenotype and reconstitution of immunoregulatory T cell subsets after T cell-depleted allogeneic and autologous bone marrow transplantation.

In the present study, we examined changes in the expression of CD45RA, CD31, and CD29 on total CD4 and CD8 lymphocytes in patients who had received CD6 T cell-depleted allogeneic marrow and received no immune suppressive drugs after engraftment in order to identify defects in reconstitution of immunoregulatory T cells after allogeneic BMT. Results following allo-BMT were compared with normal controls and patients following autologous BMT. We showed that CD4+CD45RA+, CD4+CD29+ (CD29high), and CD4+CD31+ cells were markedly decreased during the first 24 months after allo- and auto-BMT. CD8+CD45RA+ cells recovered to normal levels within the first month after auto-BMT, while after allo-BMT, the CD8+CD45RA+ cells were at slightly low levels during the first month, but gradually increased to normal levels by 12 months post-BMT. CD8+CD29+ cells were increased during the first 12 months both after allo- and auto-BMT although during the first month, a decreased percentage of CD8+CD29+ cells was observed in allo-BMT patients. More important, CD4+CD29+, CD8+CD29+, and CD8+S6F1+ cells were significantly increased in patients with moderate-to-severe acute GVHD (grades II-IV) compared with those with or without mild acute GVHD (grade I), suggesting that CD4 helper-inducer (CD4+CD29high) and CD8 killer-effector (CD8+CD29highS6F1+) cells play an important role in the pathophysiology of acute GVHD.

Adult↗

PubMed1994

Enhancement of antigen-induced T-cell proliferation by soluble CD26/dipeptidyl peptidase IV.

The addition of a soluble recombinant CD26 (sCD26) enhanced proliferation of peripheral blood lymphocytes induced by the recall antigen tetanus toxoid. sCD26 itself did not provide a mitogenic signal and did not augment the proliferative response of T cells to other mitogenic stimuli such as phytohemagglutinin and anti-CD3. Dipeptidyl peptidase IV-negative sCD26 did not have this enhancement effect, implying a requirement for enzyme activity. It was found that there exists a large variation in the levels of human plasma sCD26/dipeptidyl peptidase IV in vivo which may regulate T-cell activity. Peripheral blood lymphocytes from individuals whose plasma sCD26 was high and responded strongly to tetanus toxoid stimulation were insensitive to the enhancing effects of exogenously added sCD26. This suggests that plasma sCD26 had modulated the responsiveness of T cells of these individuals in vivo and that the endogenous plasma sCD26 regulates immune responses by allowing antigen-specific T cells to exert a maximal response to their specific antigen.

Adjuvants, Immunologic↗

PubMed1994

CD antigens 1993.

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Antibodies, Monoclonal↗

PubMed1994

CD antigens 1993.

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Antigens, CD↗

PubMed1994

CD antigens 1993.

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Antigens, CD↗

PubMed1994

3H11, a unique cell surface molecule involved in the function of the CD45RA+ subset of CD4+ cells.

We have developed a mAb anti-3H11 by immunizing mice with a T cell line derived from the Callithrix jacchus (common marmoset). Anti-3H11 is reactive with approximately 48% of unfractionated T cells, 62% of CD4+ cells and 39% of CD8+ cells. Among CD4 cells, anti-3H11 preferentially reacts with the CD45RA+ T cell subset. The majority of helper activity for pokeweed mitogen (PWM)-driven B cell IgG synthesis and T cell response to recall antigen such as tetanus toxoid was found within the 3H11-CD4 cell population, whereas anti-3H11+CD4+ cells provided poor helper function for PWM-driven B cell IgG synthesis and were more responsive to concanavalin A and autologous mixed lymphocyte reaction. Biochemical characterization showed that anti-3H11 precipitated a single protein band with a relative molecular weight of 32,000 from 125I-surface labeled cell lysate. Biochemical, phenotypic and functional studies revealed that the 3H11 molecule appeared to be different from previously established molecules on the T cell surface. Interestingly, addition of anti-3H11 to the combination of CD4 and B cells in the presence of CD8 cells but not to the combination of CD4 and B cells resulted in enhancement of the suppression of PWM-driven B cell IgG synthesis. Moreover, anti-3H11 had a co-mitogenic effect on T cells via the CD2 and CD3 pathways, and this co-mitogenic activity is restricted to the CD45RA+ T cells. Taken together, our results show that the 3H11 molecule is a novel antigen which may play an important role in the activation and function of the CD45RA+ subset of T cells.

Animals↗