Codevelopment of dendritic cells along with erythroid differentiation from human CD34+ cells by tumor necrosis factor-α

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.

Functional comparison of the mouse DC-SIGN, SIGNR1, SIGNR3 and Langerin, C-type lectins

The mouse (m) DC-SIGN family consists of several homologous type II transmembrane proteins located in close proximity on chromosome 8 and having a single carboxyl terminal carbohydrate recognition domain. We first used transfected non-macrophage cell lines to compare the polysaccharide and microbial uptake capacities of three of these lectins--DC-SIGN, SIGNR1 and SIGNR3--to another homologue mLangerin. Each molecule shares a potential mannose-recognition EPN-motif in its carbohydrate recognition domain. Using an anti-Tag antibody to follow Tag-labeled transfectants, we found that each molecule could be internalized, although the rates differed. However, mDC-SIGN was unable to take up FITC-dextran, FITC-ovalbumin, zymosan or heat-killed Candida albicans. The other three lectins showed distinct carbohydrate recognition properties, assessed by blocking FITC-dextran uptake at 37 degrees C and by mannan binding activity at 4 degrees C. Furthermore, only SIGNR1 was efficient in mediating the capture by transfected cells of Gram-negative bacteria, such as Escherichia coli and Salmonella typhimurium, while none of the lectins tested were competent to capture Gram-positive bacteria, Staphylococcus aureus. Interestingly, transfectants with SIGNR1 lacking the cytoplasmic domain were capable of binding FITC-zymosan in a manner that was abolished by EDTA or mannan, but not laminarin. In addition, resident peritoneal CD11b+ cells expressing SIGNR1 bound zymosan at 4 degrees C in concert with a laminarin-sensitive receptor. Therefore these homologous C-type lectins have distinct recognition patters for microbes despite similarities in the carbohydrate recognition domains.

Plasmacytoid Dendritic Cells Regulate Th Cell Responses through OX40 Ligand and Type I IFNs

Dendritic cells (DCs) show a functional plasticity in determining Th responses depending on their maturational stage or on maturational signals delivered to the DCs. Human plasmacytoid DCs (PDCs) can induce either Th1- or Th2-type immune responses upon exposure to viruses or IL-3, respectively. In this study we have investigated the Th-polarizing capacity of PDCs after short (24-h) or long (72-h) culture with stimuli and have assessed the expression and function of OX40 ligand (OX40L) in PDC-mediated Th polarization in addition to type I IFN-dependent responses. IL-3-treated PDCs expressed OX40L, but produced almost no IFN-alpha in response to T cell stimulation (CD40 ligand or T cell interaction), resulting in the preferential priming of Th2 cells through OX40L-dependent mechanisms. Meanwhile, PDCs were rapidly endowed by viral infection (Sendai virus) with a high potency to develop IFN-gamma-producing Th cells depending on their capacity to residually produce IFN-alpha. Although Sendai virus-stimulated PDCs simultaneously expressed OX40L in their maturational process, the Th1-inducing effect of endogenous type I IFNs may overcome and thus conceal the OX40L-dependent Th2 responses. However, during maturation in response to Sendai virus over the longer 72-h period, the expression level of OX40L was up-regulated, whereas the residual IFN-alpha-producing ability was down-regulated, and consequently, the PDCs with prolonged Sendai virus stimulation induced Th2 responses to some extent. Thus, PDCs have the distinct means to dictate an appropriate response to environmental stimuli.

Defective development of splenic and epidermal CD4+ dendritic cells in mice deficient for IFN regulatory factor-2

Dendritic cells (DCs) play important roles in the initiation and regulation of immune responses. Although several subsets of DCs were identified according to their expression of surface molecules such as CD4, CD8, and CD11b, the regulatory mechanism for the development and homeostasis of these DC subsets remains unclear. Here we show that mice lacking IFN regulatory factor-2 (IRF-2(-/-) mice) exhibited a marked and selective defect in splenic CD4(+)CD11b(+)DCs, instead of CD8 alpha(+)CD11b(-)DCs that were reported to be missing in mice lacking the related transcription factor IRF-8. Furthermore, the numbers of epidermal Langerhans cells in IRF-2(-/-) mice were reduced at least in part because of the lack of the CD4(+)CD11b(+) subset. Studies with radiation bone marrow chimeras as well as in vitro retrovirus-mediated gene transduction showed that IRF-2 was required cell-autonomously for the development of myeloid-related DCs. Notably, these abnormalities in DCs diminished in mice lacking both IRF-2 and the IFN-alpha/beta receptor, indicating that IRF-2 acted through negatively regulating IFN-alpha/beta signals. In contrast, natural killer cells still showed developmental arrest in these double mutant mice, indicating that the mode of action of IRF-2 for CD4(+)DC development is distinct from that for natural killer cell development. Our current findings thus pointed to a previously unknown unique cell-type-selective multimode function of IRF-2 in the regulation of lymphohematopoiesis.

Hyperplastic gastric tumors induced by activated macrophages in COX-2/mPGES-1 transgenic mice

Cyclooxygenase-2 (COX-2), the rate-limiting enzyme for prostanoid biosynthesis, plays a key role in gastrointestinal carcinogenesis. Among various prostanoids, prostaglandin E2 (PGE2) appears to be most responsible for cancer development. To investigate the role of PGE2 in gastric tumorigenesis, we constructed transgenic mice simultaneously expressing COX-2 and microsomal prostaglandin E synthase (mPGES)-1 in the gastric epithelial cells. The transgenic mice developed metaplasia, hyperplasia and tumorous growths in the glandular stomach with heavy macrophage infiltrations. Although gastric bacterial counts in the transgenic mice were within the normal range, treatment with antibiotics significantly suppressed activation of the macrophages and tumorous hyperplasia. Importantly, the antibiotics treatment did not affect the macrophage accumulation. Notably, treatment of the transgenic mice with lipopolysaccharides induced proinflammatory cytokines through Toll-like receptor 4 in the gastric epithelial cells. These results indicate that an increased level of PGE2 enhances macrophage infiltration, and that they are activated through epithelial cells by the gastric flora, resulting in gastric metaplasia and tumorous growth. Furthermore, Helicobacter infection upregulated epithelial PGE2 production, suggesting that the COX-2/mPGES-1 pathway contributes to the Helicobacter-associated gastric tumorigenesis.

Ly49Q, a member of the Ly49 family that is selectively expressed on myeloid lineage cells and involved in regulation of cytoskeletal architecture

Here, we identified and characterized a Ly49 family member, designated as Ly49Q. The Ly49q gene encodes a 273-aa protein with an immunoreceptor tyrosine-based inhibitory motif (ITIM) at the N terminus of its cytoplasmic domain. We show that the ITIM of Ly49Q can recruit SHP-2 and SHP-1 in a tyrosine phosphorylation-dependent manner. In contrast to other known members of the Ly49 family, Ly49Q was found not to be expressed on NK1.1(+) cells, but instead was detectable on virtually all Gr-1(+) cells, such as myeloid precursors in bone marrow. Monocytes/macrophages also expressed low levels of Ly49Q, and the expression was enhanced by the treatment of cells with IFN-gamma. Treatment of activated macrophages with anti-Ly49Q mAb induced rapid formation of polarized actin structures, showing filopodia-like structure on one side and lamellipodial-like structure on the other side. A panel of proteins became tyrosine-phosphorylated in myeloid cells when treated with the mAb. Induction of the phosphorylation depends on the ITIM of Ly49Q. Thus, Ly49Q has unique features different from other known Ly49 family members and appears to be involved in regulation of cytoskeletal architecture of macrophages through ITIM-mediated signaling.

Photodynamic therapy for malignant biliary obstruction: a case series

We describe four elderly patients (age range 73-85 years) with bile duct carcinoma who were treated with photodynamic therapy. These patients could not be treated surgically because of the presence of cardiopulmonary disease and the extent of the bile duct carcinoma. Prior to photodynamic treatment the patients underwent percutaneous transhepatic biliary drainage (PTBD) to relieve jaundice. The photodynamic therapy was carried out under percutaneous transhepatic cholangioscopy, 2 days after intravenous administration of sodium porfimer (2 mg/kg). Excimer dye laser was used to irradiate the obstructive lesion with an energy dosage of 50 J/cm2 (total irradiation dose 150-250 J/cm2) and stenotic site with a dosage of 50-100 J/cm2. Photodynamic therapy was achieved safely without occurrence of cholangitis in all patients, and was followed by metallic stent placement, resulting in the improvement of performance levels in three patients who did not have liver metastases. Photodynamic therapy via the PTBD route is a safe and promising palliative therapy for selected elderly patients with bile duct carcinoma.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Five mouse homologues of the human dendritic cell C-type lectin, DC-SIGN

DC-SIGN, a human C-type lectin, is expressed on the surface of dendritic cells (DC), while a closely related human gene, DC-SIGNR or L-SIGN, is found on sinusoidal endothelial cells of liver and lymph node. Both DC-SIGN and DC-SIGNR/L-SIGN can bind ICAM-3 and HIV gp120, and transmit HIV to susceptible cells in trans. Here, we report the cloning of five mouse genes homologous to human DC-SIGN and DC-SIGNR/L-SIGN. Only one gene, named mouse DC-SIGN, is highly expressed in DC, and is not found in a panel of mouse macrophage and lymphocyte cell lines. The other four genes, named mouse SIGNR1 (SIGN-Related gene 1), SIGNR2, SIGNR3 and SIGNR4, are expressed at lower levels in various cells according to RT-PCR and Northern blot analyses on RNA. All the genes of mouse DC-SIGN and SIGNRs map to adjacent regions of chromosome 8 A1.2-1.3. However, like human DC-SIGN, only the mouse DC-SIGN gene is closely juxtaposed to the CD23 gene, while the other four SIGNR genes are located close to each other in a neighboring region. mRNAs of mouse DC-SIGN and three SIGNR genes encode type II transmembrane proteins (DC-SIGN, 238 amino acids; SIGNR1, 325 amino acids; SIGNR3, 237 amino acids; SIGNR4, 208 amino acids), but the SIGNR2 gene only encodes a carbohydrate recognition domain (CRD) without a cytosolic domain and a transmembrane domain (SIGNR2, 178 amino acids). Amino acid sequence similarities between the CRD of human DC-SIGN and the mouse homologues are 67% for DC-SIGN, 69% for SIGNR1, 65% for SIGNR2, 68% for SIGNR3 and 70% for SIGNR4 respectively. However, the membrane proximal neck domains in the mouse genes are much shorter than their counterparts in human DC-SIGN and DC-SIGNR/L-SIGN. This family of mouse C-type lectins is therefore complex, but only one of the new genes, DC-SIGN, is juxtaposed to CD23 and is expressed at high levels in DC.

Intrahepatic cholangiojejunostomy for unresectable malignant biliary tumors with obstructive jaundice

We reviewed our experience with intrahepatic cholangiojejunostomy as a palliative therapy for patients with unresectable malignant diseases involving the ductal confluence or the common hepatic duct. Fifteen patients with malignant biliary obstruction were treated by cholangiojejunostomy at our hospital. Two patients had intrahepatic cholangiocarcinoma, 7 had gallbladder carcinoma, 5 had bile duct carcionoma, and 1 had pancreatic carcinoma. Segment III cholangiojejunostomies were performed in 14 patients and segment V cholangiojejunostomy in 1. Contraindications for surgical resection were locoregional invasion of tumors involving the proper and/or common hepatic artery and portal vein in 15 patients and the presence of hepatic metastases in 6 patients. Liver metastases were detected in 5 of the 7 patients with gallbladder carcinoma. Postoperative complications occurred in 2 patients (13%), but there was no leakage of the cholangioenteric anastomosis in our series. There was no operative mortality after cholangiojejunostomy. Of the 9 patients who survived for more than 6 months after surgery, 7 showed a significant improvement in performance status (PS) (82 +/- 10%) 3 months after the surgery compared with the preoperative PS (70 +/- 7%). Four of the 9 patients had recurrent cholangitis as a late complication, but 4 were completely free from jaundice. Median survival after cholangioenteric bypass was 9 months (range, 2-25 months). With respect to tumor location, the median survival time was 4 months (range, 2-25 months) in patients with gallbladder carcinoma and 15.5 months (range, 12-22 months) in those with bile duct carcinoma. While the median survival period after surgery was only 3 months (range, 2 to 8 months) in the 5 patients with hepatic metastases from gallbladder carcinoma, 2 patients without liver metastasis survived for 9 and 25 months after segment III cholangioenteric bypass. In conclusion, cholangiojejunostomy can provide useful palliation for malignant biliary obstruction when combined with careful patient selection.