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Biomedical subjects

Kayo Inaba

Publications and source records attributed to Kayo Inaba.

33 records · Page 2Linked to original sources
PubMed2004

Codevelopment of dendritic cells along with erythroid differentiation from human CD34(+) cells by tumor necrosis factor-alpha.

OBJECTIVE: Tumor necrosis factor-alpha (TNF-alpha) inhibits erythropoiesis and enhances nonerythroid colony formation. The present study examines the nature of these nonerythroid cells and investigates their physiologic role in relation to erythroid progenitor cells. MATERIALS AND METHODS: Highly purified human CD34(+) cells underwent erythroid differentiation in the presence of multiple cytokines, including stem cell factor (SCF), interleukin-3 (IL-3), and erythropoietin (EPO), with and without TNF-alpha. We enumerate colony-forming unit-erythroid (CFU-E) and glycophorin A (GPA; a specific marker for erythroid lineage) positive cells in semisolid phase as well as in liquid suspension culture. The character and roles of codeveloping nonerythroid cells in the presence of TNF-alpha were analyzed using fluorescent activating cell sorter, enzyme immunohistochemistry, and confocal microscopy. RESULTS: TNF-alpha inhibited the generation of GPA(+) cells and conversely enhanced the generation of GPA(-) cells. The GPA(-) cells were comprised of cells with excentric cell shape and were positive for HLA class I, HLA class II, CD1a, CD4, CD11c, CD14, CD40, CD80, CD83, and CD86, but not for CD3, CD8, CD19, CD20, and CD56, indicating the codevelopment of dendritic cells (DC) along with erythroid differentiation. Developing DC/DC precursors were detected within 3 days of culture. Only in the presence of TNF-alpha did CD34(+) cells proliferate by forming aggregates where both GPA(+) and CD11c(+) DC/DC precursors were present. During culture period, immature CD11c(+) DC were capable of endocytosing damaged GPA(+) cells. CONCLUSIONS: GPA(-) cells cogenerated from human CD34(+) cells during erythroid differentiation in the presence of IL-3/SCF/EPO and TNF-alpha express DC phenotypes. The CD11c(+) DC subset physically and selectively associates with developing immature erythroid cells and damaged self-GPA(+) cells and then obtains and captures self-substances.

Antigens, CD34↗
PubMed2003

Direct expansion of functional CD25+ CD4+ regulatory T cells by antigen-processing dendritic cells.

An important pathway for immune tolerance is provided by thymic-derived CD25+ CD4+ T cells that suppress other CD25- autoimmune disease-inducing T cells. The antigen-presenting cell (APC) requirements for the control of CD25+ CD4+ suppressor T cells remain to be identified, hampering their study in experimental and clinical situations. CD25+ CD4+ T cells are classically anergic, unable to proliferate in response to mitogenic antibodies to the T cell receptor complex. We now find that CD25+ CD4+ T cells can proliferate in the absence of added cytokines in culture and in vivo when stimulated by antigen-loaded dendritic cells (DCs), especially mature DCs. With high doses of DCs in culture, CD25+ CD4+ and CD25- CD4+ populations initially proliferate to a comparable extent. With current methods, one third of the antigen-reactive T cell receptor transgenic T cells enter into cycle for an average of three divisions in 3 d. The expansion of CD25+ CD4+ T cells stops by day 5, in the absence or presence of exogenous interleukin (IL)-2, whereas CD25- CD4+ T cells continue to grow. CD25+ CD4+ T cell growth requires DC-T cell contact and is partially dependent upon the production of small amounts of IL-2 by the T cells and B7 costimulation by the DCs. After antigen-specific expansion, the CD25+ CD4+ T cells retain their known surface features and actively suppress CD25- CD4+ T cell proliferation to splenic APCs. DCs also can expand CD25+ CD4+ T cells in the absence of specific antigen but in the presence of exogenous IL-2. In vivo, both steady state and mature antigen-processing DCs induce proliferation of adoptively transferred CD25+ CD4+ T cells. The capacity to expand CD25+ CD4+ T cells provides DCs with an additional mechanism to regulate autoimmunity and other immune responses.

Animals↗
PubMed2003

Dendritic cell immunoactivating receptor, a novel C-type lectin immunoreceptor, acts as an activating receptor through association with Fc receptor gamma chain.

An increasing number of C-type lectin receptors are being discovered on dendritic cells, but their signaling abilities and underlying mechanisms require further definition. Among these, dendritic cell immunoreceptor (DCIR) induces negative signals through an inhibitory immunoreceptor tyrosine-based inhibitory motif (ITIM) in its cytoplasmic tail. Here we identify a novel C-type lectin receptor, dendritic cell immunoactivating receptor (DCAR), whose extracellular lectin domain is highly homologous to that of DCIR. DCAR is expressed similarly in tissues to DCIR, but its short cytoplasmic portion lacks signaling motifs like ITIM. However, a positively charged arginine residue is present in the transmembrane region of the DCAR, which may explain its association with Fc receptor gamma chain and its stable expression on the cell surface. Furthermore, cross-linking of DCAR in the presence of gamma chain activates calcium mobilization and tyrosine phosphorylation of cellular proteins. These signals are mediated by the immunoreceptor tyrosine-based activating motif (ITAM) of the gamma chain. Thus, DCAR is closely related to DCIR, but it introduces activating signals into antigen-presenting cells through its physical and functional association with ITAM-bearing gamma chain. The identification of this activating immunoreceptor provides an example of signaling via a dendritic cell-expressed C-type lectin receptor.

Amino Acid Motifs↗
PubMed2003

Prostaglandin E2-EP4 signaling initiates skin immune responses by promoting migration and maturation of Langerhans cells.

Antigen-specific immune responses in the skin are initiated by antigen uptake into Langerhans cells and the subsequent migration of these cells to draining lymph nodes. Although prostaglandin E2 (PGE2) is produced substantially in skin exposed to antigen, its role remains unclear. Here we show that although Langerhans cells express all four PGE receptor subtypes, their migration to regional lymph nodes was decreased only in EP4-deficient (Ptger4-/-) mice and in wild-type mice treated with an EP4 antagonist. An EP4 agonist promoted the migration of Langerhans cells, increased their expression of costimulatory molecules and enhanced their ability to stimulate T cells in the mixed lymphocyte reaction in vitro. Contact hypersensitivity to antigen was impaired in Ptger4-/- mice and in wild-type mice treated with the EP4 antagonist during sensitization. PGE2-EP4 signaling thus facilitates initiation of skin immune responses by promoting the migration and maturation of Langerhans cells.

Animals↗
PubMed2003

TH2 dominance and defective development of a CD8+ dendritic cell subset in Id2-deficient mice.

BACKGROUND: Although the TH1/TH2 balance is important in many clinical situations, the regulatory mechanisms in vivo have not been well elucidated. OBJECTIVE: We sought to characterize the immunologic status of mice lacking Id2, an inhibitor of basic helix-loop-helix transcription factors. METHODS: We analyzed serum immunoglobulin levels, gene-expression profiles in the spleen, TH1/TH2 balance, and dendritic cell (DC) populations of Id2-/- mice. RESULTS: Serum levels of TH2-mediated IgG1 and IgE were increased more than 10-fold in Id2-/- mice without antigenic stimulation. Gene-expression analysis in Id2-/- splenocytes revealed enhanced expression of TH2-related genes, such as IL-4, and reduced expression of TH1-related genes, including IFN-gamma and IL-12. Intracellular cytokine staining also confirmed that Id2-/- splenic CD4+ T cells are substantially skewed to TH2 cells. However, Id2-/- naive CD4+ T cells differentiated into TH1 cells comparably with wild-type T cells under the appropriate culture conditions. Id2-/- mice displayed a selective and remarkable reduction of the CD8+ DC subset, which is known to induce preferential TH1 differentiation. CONCLUSION: Id2 is an indispensable regulator of the TH1/TH2 balance, possibly through the proper development of CD8alpha+ DCs, and could be a novel target to treat allergic diseases.

Animals↗
PubMed2003

SIGN-R1, a novel C-type lectin expressed by marginal zone macrophages in spleen, mediates uptake of the polysaccharide dextran.

The marginal zone macrophages of the spleen are implicated in the clearance of polysaccharides, but underlying mechanisms need to be pinpointed. SIGN-R1 is one of five recently identified mouse genes that are homologous to human DC-SIGN and encode a single, external, C-terminal C-type lectin domain. We find that a polyclonal antibody to a specific SIGN-R1 peptide reacts primarily and strongly with a subset of macrophages in the marginal zone of spleen and lymph node medulla. In both sites, SIGN-R1 exists primarily in an aggregated form, resistant to dissociation into monomers upon boiling in SDS under reducing conditions. Upon transfection into three different cell lines, high-mol.-wt forms bearing SIGN-R1 are expressed, as well as reactivity with ER-TR9, a mAb previously described to react selectively with marginal zone macrophages. SIGN-R1-expressing macrophages preferentially sequester dextrans following i.v. injection. Likewise, when phagocytic cells are enriched from spleen and tested in culture, dextran is selectively endocytosed by a subset of very large SIGN-R1(+) cells representing approximately 5% of total released macrophages. Uptake of FITC-dextran by these macrophages in vivo and in vitro is blocked by ER-TR9 and polyclonal anti-SIGN-R1 antibodies. Following transfection with SIGN-R1, cell lines become competent to endocytose dextrans. The dextran localizes primarily to compartments lacking transferrin receptor and the LAMP-1 CD107a panlysosomal antigen. Therefore, SIGN-R1 mediates the uptake of dextran polysaccharides, and it is predominantly expressed in the macrophages of the splenic marginal zone and lymph node medulla.

Animals↗
PubMed2003

Dendritic cell function in vivo during the steady state: a role in peripheral tolerance.

The avoidance of autoimmunity requires mechanisms to actively silence or tolerize self reactive T cells in the periphery. During infection, dendritic cells are not only capturing microbial antigens, but also are processing self antigens from dying cells as well as innocuous environmental proteins. Since the dendritic cells are maturing in response to microbial and other stimuli, peptides will be presented from both noxious and innocuous antigens. Therefore it would be valuable to have mechanisms whereby dendritic cells, prior to infection, establish tolerance to those self and environmental antigens that can be processed upon pathogen encounter. In the steady state, prior to acute infection and inflammation, dendritic cells are in an immature state and not fully differentiated to carry out their known roles as inducers of immunity. These immature cells are not inactive, however. They continuously circulate through tissues and into lymphoid organs, capturing self antigens as well as innocuous environmental proteins. Recent experiments have provided direct evidence that antigen-loaded immature dendritic in vivo silence T cells either by deleting them or by expanding regulatory T cells. In this way, it is proposed that the immune system overcomes at least some of the risk of developing autoimmunity and chronic inflammation. It is proposed that dendritic cells play a major role in defining immunologic self, not only centrally in the thymus but also in the periphery.

Animals↗
PubMed2003

Relation between serum 3-deoxyglucosone and development of diabetic microangiopathy.

OBJECTIVE: 3-Deoxyglucosone (3-DG), a highly reactive intermediate of the glycation reaction, has been suggested to contribute to the development of diabetes complications. To verify this hypothesis, we assessed the relation between serum 3-DG concentrations and the severity of diabetic microangiopathy in diabetic patients. RESEARCH DESIGN AND METHODS: We conducted a high-performance liquid chromatography assay to determine the serum 3-DG concentrations of 110 diabetic patients with different degrees of severity of diabetic microangiopathy and 57 age-matched control subjects. RESULTS: The fasting serum 3-DG level in diabetic patients was significantly (P < 0.001) higher than that in control subjects (353 +/- 110 vs. 199 +/- 53 nmol/l). The 3-DG levels were significantly (P < 0.001) elevated even in the diabetic patients showing normoalbuminuria (n = 62, 322 +/- 79 nmol/l) compared with control subjects. The 3-DG levels were further elevated in the patients with microalbuminuria (n = 30, 383 +/- 146 nmol/l) and overt proteinuria (n = 18, 410 +/- 100 nmol/l) (P = 0.027 and P < 0.001 vs. normoalbuminuria group, respectively). This phenomenon was basically reproduced in a category of retinopathy. Furthermore, the diabetic patients with low nerve conduction velocity showed a tendency to display higher 3-DG levels. CONCLUSIONS: The present results show that the fasting serum 3-DG level is elevated in diabetic patients and that the patients with relatively higher 3-DG levels were prone to suffer from more severe complications, indicating a possible association of 3-DG with diabetic microangiopathy.

Adult↗
PubMed2002

Immune tolerance after delivery of dying cells to dendritic cells in situ.

Peripheral immune tolerance is believed to be induced by the processing and presentation of self-tissues that die during physiologic tissue turnover. To examine the mechanism that mediates tolerance, we injected mice with dying syngeneic TAP(-/-) splenocytes loaded with small amounts of the protein antigen, ovalbumin (OVA). After ingestion and presentation of cell-associated OVA by the CD8(+) subset of dendritic cells in situ, large numbers of antigen-reactive, CD8(+) T cell receptor (TCR) transgenic T lymphocytes were driven into cell cycle, but then the T cells were deleted. The animals were also tolerant to challenge with OVA in complete Freund's adjuvant. An agonistic anti-CD40 monoclonal antibody was then administered together with the OVA-loaded splenocytes, so that the dendritic cells in the recipient mice would mature. In contrast to observations made in the steady state, the antigen-reactive T cells expanded in numbers for 1-2 wk and produced large amounts of interleukin 2 and interferon gamma, while the animals retained responsiveness to antigen rechallenge. The specific tolerance that develops when dendritic cells process self tissues in the steady state should prevent or reduce the development of autoimmunity when dying cells are subsequently processed during infection.

Adoptive Transfer↗
PubMed2002

The CD8+ dendritic cell subset selectively endocytoses dying cells in culture and in vivo.

Dendritic cells (DCs) are able in tissue culture to phagocytose and present antigens derived from infected, malignant, and allogeneic cells. Here we show directly that DCs in situ take up these types of cells after fluorescent labeling with carboxyfluorescein succinimidyl ester (CFSE) and injection into mice. The injected cells include syngeneic splenocytes and tumor cell lines, induced to undergo apoptosis ex vivo by exposure to osmotic shock, and allogeneic B cells killed by NK cells in situ. The CFSE-labeled cells in each case are actively endocytosed by DCs in vivo, but only the CD8+ subset. After uptake, all of the phagocytic CD8+ DCs can form major histocompatibility complex class II-peptide complexes, as detected with a monoclonal antibody specific for these complexes. The CD8+ DCs also selectively present cell-associated antigens to both CD4+ and CD8+ T cells. Similar events take place with cultured DCs; CD8+ DCs again selectively take up and present dying cells. In contrast, both CD8+ and CD8- DCs phagocytose latex particles in culture, and both DC subsets present soluble ovalbumin captured in vivo. Therefore CD8+ DCs are specialized to capture dying cells, and this helps to explain their selective ability to cross present cellular antigens to both CD4+ and CD8+ T cells.

Animals↗
PubMed2002

DCIR acts as an inhibitory receptor depending on its immunoreceptor tyrosine-based inhibitory motif.

Major histocompatibility complex class II positive cells, namely dendritic cells, monocytes/macrophages, and B cells, are categorized as antigen-presenting cells. Dendritic cells, so-called professional antigen-presenting cells, use distinct sets of surface receptors before and after maturation: those to capture antigens and those to interact with T cells, respectively. But there remain many surface molecules whose functions are still unknown. In this study, we isolated dendritic cell immunoreceptor from mouse bone-marrow-derived mature dendritic cells. Dendritic cell immunoreceptor is a recently reported C-type lectin receptor characteristic with cytoplasmic immunoreceptor tyrosine-based inhibitory motif. Expression of mouse dendritic cell immunoreceptor mRNA was observed specifically in spleen and lymph node, slightly increased with dendritic cell maturation during in vitro culture of bone marrow cells, and was not detected in cultured natural killer cells. Surface expression of mouse dendritic cell immunoreceptor protein was observed in splenic antigen-presenting cells including B cells, monocytes/macrophages, and dendritic cells, but not in T cells. To reveal the downregulating capacity of dendritic cell immunoreceptor in antigen-presenting cells, the change of B-cell-receptor-mediated signals after coligation with a chimeric Fcgamma receptor IIB containing the cytoplasmic portion of mouse dendritic cell immunoreceptor was examined. As a result, we detected two distinct inhibitory effects of cytoplasmic dendritic cell immunoreceptor minus sign inhibition of B-cell-receptor-mediated Ca2+ mobilization and protein tyrosine phosphorylation minus sign and both of these effects required the tyrosine residue inside the immunoreceptor tyrosine-based inhibitory motif. This report presents immunoreceptor tyrosine-based inhibitory motif-dependent negative regulatory function of dendritic cell immunoreceptors. In conclusion, mouse dendritic cell immunoreceptor expressed on antigen-presenting cells can exert two distinct inhibitory signals depending on its immunoreceptor tyrosine-based inhibitory motif tyrosine residue.

Amino Acid Motifs↗
PubMed2002

Identification and expression of mouse Langerin (CD207) in dendritic cells.

We have cloned the mouse homologue of human Langerin (h-Langerin), a type II transmembrane protein with a single external C-type lectin domain. Mouse Langerin (m-Langerin) displays 65 and 74% homologies in total amino acid and lectin domains with those of h-Langerin. The cognate mouse and rat genes were assigned to chromosome 6D1-D2 and chromosome 4q33 distal-q34.1 proximal respectively, syntenic to the h-Langerin gene on chromosome 2p13. With RT-PCR, m-Langerin transcripts were as expected detected in MHC class II+, but not MHC class II-, cells from epidermis and the expression level was reduced by culture. However, m-Langerin transcripts were also expressed in spleen, lymph nodes (LN), thymus, liver, lung and even heart, but not gut-associated lymphoid tissues. In single-cell lymphoid suspensions, m-Langerin transcripts were mainly detected in the CD11c+ dendritic cells (DC), especially the CD11blow/CD8high fraction of spleen and LN. DC generated from bone marrow precursors by granulocyte macrophage colony stimulating factor (GM-CSF) expressed m-Langerin, but this was shut down during maturation with CD40 ligand or lipopolysaccharide. DC derived from blood monocytes by GM-CSF + IL-4 lacked m-Langerin unless the cultures were supplemented with transforming growth factor (TGF)-beta1. Unexpectedly, significant amounts of m-Langerin transcripts were detected in skin and LN of TGF-beta1-deficient mice, although in much lower amounts than littermate controls. Recombinant m-Langerin could form multimers and bind to mannan-agarose. These findings indicate that Langerin expression is regulated at several levels: by TGF-beta1, DC subsets, DC maturation and the tissue environment.

Amino Acid Sequence↗
PubMed2002

Prevention of senile osteoporosis in SAMP6 mice by intrabone marrow injection of allogeneic bone marrow cells.

The SAMP6 mouse (a substrain of senescence-accelerated mice) spontaneously develops osteoporosis early in life and is, therefore, a useful model for examining the mechanisms underlying osteoporosis. We have recently established a new bone marrow transplantation (BMT) method: the bone marrow cells (BMCs) of normal allogeneic mice are directly injected into the bone marrow (BM) cavity of irradiated (5.5 Gy x 2) recipients (IBM-BMT). Using IBM-BMT, we attempted to prevent osteoporosis in SAMP6 mice. The hematolymphoid system was completely reconstituted with donor-type cells after IBM-BMT. Thus-treated SAMP6 mice showed marked increases in trabecular bones even at 12 months of age, and the bone mineral density remained similar to that of normal B6 mice. In concordance with these findings, urinary deoxypyridinoline also remained continuously low until 10 months of age, indicating that IBM-BMT was effective in the prevention of bone absorption. In addition to the above, BM stromal cells in the treated SAMP6 mice were replaced with donor stromal cells, and the message level of interleukin-11 (IL-11), which is produced by the BM stromal cells and is known as an important factor in the regulation of bone remodeling, was restored to a level similar to that observed in normal B6 mice. Furthermore, the message level of IL-6, which is known to enhance osteoclastogenesis, was also restored to normal. These results indicate that the BM microenvironment was normalized after IBM-BMT and that the increased production of IL-11 and IL-6 ameliorated the imbalance between bone absorption and formation, resulting in the prevention of osteoporosis in SAMP6 mice.

Amino Acids↗