Biomedical subjects

Yong-Jun Liu

Publications and source records attributed to Yong-Jun Liu.

At least 73 records · Page 4Linked to original sources

PubMed2004

A follow-up linkage study for bone size variation in an extended sample.

Bone size, which has strong genetic determination, is an important determinant of bone strength and a risk factor of osteoporotic fractures. We previously reported an approximately 10-cm genome-wide linkage scan in 630 subjects from 53 US Caucasian pedigrees. The strongest evidence of linkage was obtained on chromosome 17q22 near the marker D17S787, with a two-point LOD score of 3.98 and a multipoint maximum LOD score (MLS) of 3.01. Additionally, suggestive linkages (1.54 < MLS < 2.83) were found at the other four chromosomal regions. In the present study, with an attempt to further examine our previous findings, we perform a follow-up linkage analysis in an expanded sample of 79 pedigrees with 1816 subjects. The total sample contains >80,000 informative relative pairs for linkage analyses, including 3846 sib pairs. Fifteen markers covering the above five promising regions are genotyped, narrowing the average genomic distance from approximately 10 to 5 cm. In the total 79 pedigrees, support of linkage was achieved for the wrist bone size at 17q22 with a two-point LOD score of 2.27 (P = 0.0006) and MLS of 1.78 (P = 0.002). The genomic region 17q22 includes COL1A1, a strong candidate gene that is significantly associated with osteoporotic fracture risk. Our data suggest that this region is promising for further exploratory studies.

Adult↗

PubMed2004

Mysterious origin of plasmacytoid dendritic cell precursors.

The origin of plasmacytoid dendritic cell precursors (pDC) has been controversial. This manuscript shows that CLP and CMP both can give rise to pDCs. pDCs derived from CMP express RAG gene products and show IgHD-J rearrangement, suggesting that pDC represent a unique lineage whose gene expression program shows substantial plasticity.

Cell Differentiation↗

PubMed2004

Plasmacytoid dendritic cells in immunity.

Human and mouse plasmacytoid dendritic cells have been shown to correspond to a specialized cell population that produces large amounts of type I interferons in response to viruses, the so-called natural interferon-producing cells. As a result, intensive investigation is now focused on the potential functions of plasmacytoid dendritic cells in both innate and adaptive immunity. Here we review recent progress on the characterization of plasmacytoid dendritic cell origin, development, migration and function in immunity and tolerance, as well as their effect on human diseases.

Animals↗

PubMed2004

Lack of evidence for a major gene in the Mendelian transmission of BMI in Chinese.

OBJECTIVES: To determine the heritability of BMI and to examine the mode of inheritance of BMI variation in Chinese. RESEARCH METHODS AND PROCEDURES: Familial correlation and complex segregation analyses for BMI were undertaken in a Chinese sample composed of 392 nuclear families, with 1190 total individuals. RESULTS: A moderate heritability was found for BMI (h2 = 0.419-0.492). The obtained results do not support a major gene for BMI in our samples. BMI may be inherited in a complex and non-Mendelian manner in Chinese. DISCUSSION: The findings of this study suggest that identification of specific genes for BMI in Chinese, at least within the same data set, is a serious challenge because of the lack of evidence of a major gene for BMI in our Chinese sample.

Aged↗

PubMed2004

Genetic dissection of human stature in a large sample of multiplex pedigrees.

Recently, we reported a whole genome scan on a sample of 630 Caucasian subjects from 53 human pedigrees. Several genomic regions were suggested to be linked to height. In an attempt to confirm the identified genomic regions, as well as to identify new genomic regions linked to height, we conducted a whole genome linkage study on an extended sample of 1,816 subjects from 79 pedigrees, which includes the 53 pedigrees containing the original 630 subjects from our previous whole genome study and an additional 128 new subjects, and 26 further pedigrees containing 1,058 subjects. Several regions achieved suggestive linkage signals, such as 9q22.32 [MLS (multipoint LOD score) = 2.74], 9q34.3 [MLS = 2.66], Xq24 [two-point LOD score = 2.64 at the marker DXS8067], and 7p14.2 [MLS = 2.05]. The importance of the above regions is supported either by other whole genome studies or by candidate genes within these regions relevant to linear growth or pathogenesis of short stature. In addition, this study has tentatively confirmed the Xq24 region's linkage to height, as this region was also detected in the previous whole genome study. To date, our study has achieved the largest sample size in the field of genetic linkage studies of human height. Together with the findings of other studies, the current study has further delineated the genetic basis of human stature.

Adult↗

PubMed2004

Human immunodeficiency virus type 1 activates plasmacytoid dendritic cells and concomitantly induces the bystander maturation of myeloid dendritic cells.

In this study, we analyzed the phenotypic and physiological consequences of the interaction of plasmacytoid dendritic cells (pDCs) with human immunodeficiency virus type 1 (HIV-1). pDCs are one cellular target of HIV-1 and respond to the virus by producing alpha/beta interferon (IFN-alpha/beta) and chemokines. The outcome of this interaction, notably on the function of bystander myeloid DC (CD11c+ DCs), remains unclear. We therefore evaluated the effects of HIV-1 exposure on these two DC subsets under various conditions. Blood-purified pDCs and CD11c+ DCs were exposed in vitro to HIV-1, after which maturation markers, cytokine production, migratory capacity, and CD4 T-cell stimulatory capacity were analyzed. pDCs exposed to different strains of infectious or even chemically inactivated, nonreplicating HIV-1 strongly upregulated the expression of maturation markers, such as CD83 and functional CCR7, analogous to exposure to R-848, a synthetic agonist of toll-like receptor-7 and -8. In addition, HIV-1-activated pDCs produced cytokines (IFN-alpha and tumor necrosis factor alpha), migrated in response to CCL19 and, in coculture, matured CD11c+ DCs, which are not directly activated by HIV. pDCs also acquired the ability to stimulate naïve CD4+ T cells, albeit less efficiently than CD11c+ DCs. This HIV-1-induced maturation of both DC subsets may explain their disappearance from the blood of patients with high viral loads and may have important consequences on HIV-1 cellular transmission and HIV-1-specific T-cell responses.

CD11c Antigen↗

PubMed2004

Human immunoglobulin selection associated with class switch and possible tolerogenic origins for C delta class-switched B cells.

Current paradigms of peripheral B cell selection suggest that autoreactive B cells are controlled by clonal deletion, anergy, and developmental arrest. We report that changes to the human antibody repertoire likely resulting from these mechanisms both for a well-characterized autoreactivity from antibodies encoded by the V(H)4-34 gene and for other hallmarks of an autoreactive repertoire are apparent mainly for class-switched B cells and not for IgM germinal center, IgM memory, or IgM plasma cells. Other possible indicators of autoreactivity found selected with immunoglobulin class include J(H)6 gene segment usage, increased frequency of B cells with long third hypervariable regions, and distal J(kappa) gene segment bias. Of particular interest is the finding that B cells with these same characteristics are selected into the lineage of B cells that have undergone the unusual class switch from constant region C mu to C delta (C delta-CS). The C delta-CS population also displays an increased frequency of charged amino acids localized to the complementarity-determining regions, further suggesting autoreactivity, and evidence is presented that these B cells had undergone extensive receptor editing. Thus, the C delta-CS lineage may be a "sink" for B cells harboring autoreactive specificities in normal humans. A model for a new tolerizing mechanism that could account for the C delta-CS lineage is presented.

Antibodies, Monoclonal↗

PubMed2004

A follow-up linkage study for quantitative trait loci contributing to obesity-related phenotypes.

We have recently reported a whole-genome scan in a sample of 630 subjects from 53 extended pedigrees, in which several genomic regions that may contain quantitative trait loci (QTLs) for obesity were suggested. In the present study, with an attempt to confirm our previous findings, we performed a follow-up linkage study in an expanded sample of 79 pedigrees with 1816 subjects (including expanded previous 53 pedigrees and 26 newly recruited pedigrees containing 1058 subjects). A new set of microsatellite markers spanning previously identified regions were selected, with the average genomic distance narrowed from approximately 10 cM to approximately 5 cM in this study. Using a variance component method, we performed two- and multipoint linkage analyses in the following three sample sets: expanded previous 53 pedigrees (758 subjects), 26 new pedigrees, and 79 total pedigrees. For body mass index, analyses of the expanded 53 pedigrees attained a LOD score of 2.32 near marker D1S468 in two-point analysis and a maximum LOD score (MLS) of 2.21 in multipoint analysis; 2q14 near marker D2S347 attained a LOD score of 3.42 in two-point analysis and a MLS of 3.93 in multipoint analysis. The linkage peaks at 1p36 and 2q14 were further supported in the analyses of all 79 pedigrees, with multipoint MLS being 1.38 and 0.90, respectively. For fat mass, genomic region 6q27 achieved a LOD score of 1.24 in two-point analysis and an MLS of 0.92 in multipoint analysis in all 79 pedigrees. Our data support that 1p36, 2q14, and 6q27 are promising regions that may harbor QTLs for obesity phenotypes.

Adult↗

PubMed2004

[Changes of the migration ability of the cord blood CD(34)(+) cells during short-term ex vivo expansion].

OBJECTIVE: To study the effect of ex vivo expansion on the migration ability and the CXCR4 expression of umbilical cord blood (CB) hematopoietic stem/progenitor cells (HSPC). METHODS: CD(34)(+) cells isolated from fresh CB samples were cultured in a serum-free and stroma-free culture system. On day 7, 10 and 14, CD(34)(+) cells were re-selected from the expanded cells, and the expression of CXCR4 and the transmigration ability of these CD(34)(+) cells were evaluated respectively and compared with those of the precultured fresh CD(34)(+) cells. RESULTS: (1) SDF-1 induced a higher migration percentage of fresh or expanded CB CD(34)(+) cells than that of uninduced ones. (2) Both of the uninduced and SDF-1-induced migrations were slightly reduced in the first week and then much more reduced in the second week expansion (P < 0.05). (3) The number of the CD(34)(+)CXCR4(+) cells were significantly increased during the culture period, but there was a downtrend of CXCR4 expression on CD(34)(+) subset; the expression levels on day 10 and 14 were lower than that on day 0. CONCLUSIONS: The expanded HSPC would sustain the chemotactic activity during one-week-culture, but with further extended culture time their intrinsic homing potential would be partly impaired.

Antigens, CD34↗

PubMed2003

Mature dendritic cells can enhance CD8+ cell noncytotoxic anti-HIV responses: the role of IL-15.

The CD8+ cell noncytotoxic anti-HIV response (CNAR) is associated with a long-term healthy clinical state in HIV-infected individuals. Over time CNAR is reduced concomitant with progression to disease. In studies to evaluate whether the interaction between CD8+ cells and dendritic cells (DCs) could increase CNAR, CD8+ cells from individuals who showed a decrease in this antiviral activity were cocultured with monocyte-derived dendritic cells matured with CD40 ligand. After coculture with these mature DCs, the CD8+ cells showed an increase in CNAR greater than that observed with CD8+ cells costimulated with CD3/CD28 antibodies. This antiviral response appeared to be mediated primarily by production of interleukin-15 (IL-15) by the mature DCs. Purified IL-15 also enhanced CNAR, whereas IL-12 showed no substantial effect. These studies provide another potential approach by which the immune system in HIV infection could be restored by cytokine therapy, particularly IL-15 administration.

CD3 Complex↗

PubMed2003

Thrombopoietin cooperates with FLT3-ligand in the generation of plasmacytoid dendritic cell precursors from human hematopoietic progenitors.

Type 1 interferon-producing cells (IPCs), also known as plasmacytoid dendritic cell (DC) precursors, represent the key effectors in antiviral innate immunity and triggers for adaptive immune responses. IPCs play important roles in the pathogenesis of systemic lupus erythematosus (SLE) and in modulating immune responses after hematopoietic stem cell transplantation. Understanding IPC development from hematopoietic progenitor cells (HPCs) may provide critical information in controlling viral infection, autoimmune SLE, and graft-versus-host disease. FLT3-ligand (FLT3-L) represents a key IPC differentiation factor from HPCs. Although hematopoietic cytokines such as interleukin-3 (IL-3), IL-7, stem cell factor (SCF), macrophage-colony-stimulating factor (M-CSF), and granulocyte M-CSF (GM-CSF) promote the expansion of CD34+ HPCs in FLT3-L culture, they strongly inhibit HPC differentiation into IPCs. Here we show that thrombopoietin (TPO) cooperates with FLT3-L, inducing CD34+ HPCs to undergo a 400-fold expansion in cell numbers and to generate more than 6 x 10(6) IPCs per 10(6) CD34+ HPCs within 30 days in culture. IPCs derived from HPCs in FLT3-L/TPO cultures display blood IPC phenotype and have the capacity to produce large amounts of interferon-alpha (IFN-alpha) and to differentiate into mature DCs. This culture system, combined with the use of adult peripheral blood CD34+ HPCs purified from G-CSF-mobilized donors, permits the generation of more than 10(9) IPCs from a single blood donor.

Antigens, CD↗

PubMed2003

Human thymic stromal lymphopoietin: a novel epithelial cell-derived cytokine and a potential key player in the induction of allergic inflammation.

Allergy is the result of a complex immune cascade leading to the dysregulated production of Th2 cytokines, the generation of allergen-specific IgE-producing B cells and the subsequent activation and degranulation of mast cells upon allergen challenge. Dendritic cells (DCs) play an important role in several models of allergy, but factors instructing DCs to induce a dysregulated Th2 response are currently unknown. In this review, we present recent evidence that human thymic stromal lymphopoietin (TSLP), a novel IL-7-like cytokine, might represent an early trigger of the allergic immune cascade. TSLP-activated human DCs produce Th2-attracting chemokines but no IL-12, and induce naive CD4(+) and CD8(+) T cell differentiation into effector cells with a typical pro-allergic phenotype. TSLP is produced by human epithelial, stromal, and mast cells. It is highly expressed by the keratinocytes of atopic dermatitis but not in other types of skin inflammation. Thus, epithelial- and stromal-cell-derived TSLP might represent one of the factors initiating the allergic responses, and could be a target for a curative therapeutic approach to allergy.

Animals↗

PubMed2003

Estrogen receptor alpha and vitamin D receptor gene polymorphisms and bone mineral density: association study of healthy pre- and postmenopausal Chinese women.

In the present study, we tested the association between the estrogen receptor alpha (ER-alpha) and vitamin D receptor (VDR) genes with bone mineral density (BMD). A total of 649 healthy Chinese women, classified as pre-menopausal (N=388) and post-menopausal (N=261) groups, were genotyped at the ER-alpha PvuII, XbaI, and VDR ApaI sites. BMDs at the lumbar spine (L(1)-L(4)) and total hip were measured by dual-energy X-ray absorptiometry. For the VDR ApaI locus, AA carriers had lower spine BMD than Aa (p=0.02) and aa carriers (p<0.01) in the pre-menopausal group. For the ER-alpha gene, carriers of haplotype px had lower spine BMD than the non-carriers (p=0.03) in the pre-menopausal group. Furthermore, we observed significant interaction between the ER-alpha and VDR genes in the post-menopausal group: with AA genotype (or A allele) at the VDR ApaI locus, pX carriers had higher spine BMD than the non-carriers (p=0.02), and PX carriers had lower hip BMD than the non-carriers (p=0.04). Our data suggest that the ER-alpha and VDR genes may be associated with the BMD variation in Chinese women.

Absorptiometry, Photon↗

PubMed2003

Several genomic regions potentially containing QTLs for bone size variation were identified in a whole-genome linkage scan.

Bone size is an important determinant of osteoporotic fractures. For a sample of 53 pedigrees that contains more than 10,000 relative pairs informative for linkage analyses, we performed a whole-genome linkage scan using 380 microsatellite markers to identify genomic regions that may contain QTLs of bone size (two dimensional measurement by dual energy X-ray absorptiometry). We conducted two- and multi-point linkage analyses. Several potentially important genomic regions were identified. For example, the genomic region 17q23 may contain a QTL for wrist (ultra distal) bone size variation; a LOD score of 3.98 is achieved at D17S787 in two-point analyses and a maximum LOD score (MLS) of 3.01 is achieved in multi-point analyses in 17q23. 19p13 may contain a QTL for hip bone size variation; a LOD score of 1.99 is achieved at D19S226 in two-point analyses and a MLS of 2.83 is achieved in 19p13 in multi-point analyses. The genomic region identified on chromosome 17 for wrist bone size seems to be consistent with that identified for femur head width variation in an earlier whole-genome scan study. The genomic regions identified in this study and an earlier investigation on one-dimensional bone size measurement by radiography are compared. The two studies may form a basis for further exploration with larger samples and/or denser markers for confirmation and fine mapping studies to eventually identify major functional genes and the associated etiology for osteoporosis.

Age Factors↗

PubMed2003

Human dendritic cells activated by TSLP and CD40L induce proallergic cytotoxic T cells.

Human thymic stromal lymphopoietin (TSLP) is a novel epithelial cell-derived cytokine, which induces dendritic cell (DC)-mediated CD4+ T cell responses with a proallergic phenotype. Although the participation of CD8+ T cells in allergic inflammation is well documented, their functional properties as well as the pathways leading to their generation remain poorly understood. Here, we show that TSLP-activated CD11c+ DCs potently activate and expand naive CD8+ T cells, and induce their differentiation into interleukin (IL)-5 and IL-13-producing effectors exhibiting poor cytolytic activity. Additional CD40L triggering of TSLP-activated DCs induced CD8+ T cells with potent cytolytic activity, producing large amounts of interferon (IFN)-gamma, while retaining their capacity to produce IL-5 and IL-13. These data further support the role of TSLP as initial trigger of allergic T cell responses and suggest that CD40L-expressing cells may act in combination with TSLP to amplify and sustain pro-allergic responses and cause tissue damage by promoting the generation of IFN-gamma-producing cytotoxic effectors.

CD11c Antigen↗

PubMed2003

Alkyl monolayer passivated metal-semiconductor diodes: 2: Comparison with native silicon oxide.

To understand the electrical properties at passivated metal-semiconductor interfaces, two types of mercury-insulator-silicon (n-type) junctions, Hg\C10H21-Si and Hg\SiO2-Si, were fabricated and their current-voltage and capacitance-voltage characteristics compared. Both of them exhibited near-ideal rectifying characteristics with an excellent saturation current at reverse bias, which is in contrast to the previously reported ohmic behavior of an unmodified mercury-silicon junction. The experimental results also indicated that the n-decyl monolayer passivated junction possesses a higher effective barrier height, a lower ideality factor (that is, closer to unity), and better reproducibility than that of native silicon oxide. In addition, the dopant density and build-in potential, extracted from capacitance-voltage measurements of these passivated mercury-silicon junctions, revealed that alkyl monolayer derivatization does not alter the intrinsic properties of the silicon substrate. The calculated surface state density at the alkyl monolayer\silicon interface is lower than that of the silicon oxide\silicon interface. The present study increases the possibility of using advanced organic materials as ultrathin insulator layers for miniaturized, silicon-based microelectronic devices.

Journal Article↗

PubMed2003

Heterogeneity of dendritic cells in the mouse liver: identification and characterization of four distinct populations.

Liver dendritic cells (DC) are believed to play important roles in liver immunity, autoimmunity, and in the regulation of hepatic allograft acceptance. However, limited information is available on the phenotypes and functions of DC in the liver. To address this issue, we isolated DC from murine liver using procedures that do not involve collagenase, and characterized the freshly isolated DC population that had not been subjected to in vitro expansion. Thence, based on the expression of CD4, B220, and CD11b, four subsets or groups of hepatic NK1.1(-)CD11c(+) DC were identified with the following phenotypes: B220(+)CD4(+), B220(+)CD4(-), B220(-)CD11b(+), and B220(-)CD11b(-). Each subset was further characterized both phenotypically and functionally. In addition to unique phenotypic expression, each subset displayed different allostimulation capability in mixed lymphocyte reaction assays. All four groups developed DC morphology following in vitro culture with activation agents and synthesized distinct patterns of cytokines in response to different stimuli. Taken together, our results suggest that groups I and II are IFN-alpha-producing plasmacytoid DC, group III cells are myeloid-related DC, while group IV is a heterogeneous population containing both myeloid- and lymphoid-related DC. Our results demonstrate the highly heterogeneous nature of hepatic DC, which is in agreement with the unique requirements for APC in the complex liver environment.

Animals↗

PubMed2003

Flexibility of mouse classical and plasmacytoid-derived dendritic cells in directing T helper type 1 and 2 cell development: dependency on antigen dose and differential toll-like receptor ligation.

Distinct dendritic cell (DC) subsets have been suggested to be preprogrammed to direct either T helper cell (Th) type 1 or Th2 development, although more recently different pathogen products or stimuli have been shown to render these DCs more flexible. It is still unclear how distinct mouse DC subsets cultured from bone marrow precursors, blood, or their lymphoid tissue counterparts direct Th differentiation. We show that mouse myeloid and plasmacytoid precursor DCs (pDCs) cultured from bone marrow precursors and ex vivo splenic DC subsets can induce the development of both Th1 and Th2 effector cells depending on the dose of antigen. In general, high antigen doses induced Th1 cell development whereas low antigen doses induced Th2 cell development. Both cultured and ex vivo splenic plasmacytoid-derived DCs enhanced CD4(+) T cell proliferation and induced strong Th1 cell development when activated with the Toll-like receptor (TLR)9 ligand CpG, and not with the TLR4 ligand lipopolysaccharide (LPS). The responsiveness of plasmacytoid pDCs to CpG correlated with high TLR9 expression similarly to human plasmacytoid pDCs. Conversely, myeloid DCs generated with granulocyte/macrophage colony-stimulating factor enhanced Th1 cell development when stimulated with LPS as a result of their high level of TLR4 expression. Polarized Th1 responses resulting from high antigen dose were not additionally enhanced by stimulation of DCs by TLR ligands. Thus, the net effect of antigen dose, the state of maturation of the DCs together with the stimulation of DCs by pathogen-derived products, will determine whether a Th1 or Th2 response develops.

Animals↗