Biomedical subjects

Xinjian Chen

Publications and source records attributed to Xinjian Chen.

8 recordsLinked to original sources

PubMed2006

H2-O expression in primary dendritic cells.

H2-O is a nonpolymorphic class II molecule whose biological role remains to be determined. H2-O modulates H2-M function, and it has been generally believed to be expressed only in B lymphocytes and thymic medullary epithelial cells, but not in dendritic cells (DCs). In this study, we report identification of H2-O expression in primary murine DCs. Similar to B cells, H2-O is associated with H2-M in DCs, and its expression is differentially regulated in DC subsets as well as during cell maturation and activation. Primary bone marrow DCs and plasmacytoid DCs in the spleen and lymph nodes express MHC class II and H2-M, but not the inhibitor H2-O. In contrast, myeloid DCs in secondary lymphoid organs express both H2-M and H2-O. In CD8alphaalpha(+) DCs, the ratio of H2-O to H2-M is higher than in CD8alphaalpha(-) DCs. In DCs generated from GM-CSF- and IL-4-conditioned bone marrow cultures, H2-O expression is not detected regardless of the maturation status of the cells. Administration of LPS induces in vivo activation of myeloid DCs, and this activation is associated with down-regulation of H2-O expression. Primary splenic DCs from H2-O(-/-) and H2-O(+/+) mice present exogenous protein Ags to T cell hybridomas similarly well, but H2-O(-/-) DCs induce stronger allogeneic CD4 T cell response than the H2-O(+/+) DCs in mixed leukocyte reactions. Our results suggest that H2-O has a broader role than previously appreciated in regulating Ag presentation.

Animals↗

PubMed2006

A new algorithm for distorted fingerprints matching based on normalized fuzzy similarity measure.

Coping with nonlinear distortions in fingerprint matching is a challenging task. This paper proposes a novel algorithm, normalized fuzzy similarity measure (NFSM), to deal with the nonlinear distortions. The proposed algorithm has two main steps. First, the template and input fingerprints were aligned. In this process, the local topological structure matching was introduced to improve the robustness of global alignment. Second, the method NFSM was introduced to compute the similarity between the template and input fingerprints. The proposed algorithm was evaluated on fingerprints databases of FVC2004. Experimental results confirm that NFSM is a reliable and effective algorithm for fingerprint matching with nonliner distortions. The algorithm gives considerably higher matching scores compared to conventional matching algorithms for the deformed fingerprints.

Algorithms↗

PubMed2005

Synthesis and phosphodiesterase 5 inhibitory activity of novel pyrido[1,2-e]purin-4(3H)-one derivatives.

Synthesis and primary SAR of a novel series of 2-phenylpyrido[1,2-e]purin-4(3H)-one derivatives with piperazinyl sulfonamide substituents were described herein. As potential PDE5 inhibitors for erectile dysfunction (ED) treatment, representative compounds exhibit improved selectivity versus PDE1 and PDE6. Meanwhile, compound 3e demonstrated functional efficacy on rabbit corpus cavernosum strip in vitro.

3',5'-Cyclic-GMP Phosphodiesterases↗

PubMed2004

The expression of HLA-DO (H2-O) in B lymphocytes.

HLA-DO (H2-O in mice) is a nonpolymorphic transmembrane alphabeta heterodimer encoded in the class II region of the major histocompatibility complex (MHC). It is expressed selectively in B lymphocytes and thymic medullary epithelial cells. DO forms a stable complex with the peptide-loading catalyst HLA-DM in the endoplasmic reticulum (ER); in the absence of DM, DO is unstable. During intracellular transport and distribution in the endosomal compartments, the ratio of DO to DM changes. In primary B cells, only approx 50% of DM molecules are associated with DO. DO appears to regulate the peptide-loading function of DM in the MHC class II antigen-presentation pathway. Although certain discrepancies are present, results from most studies indicate that DO (as well as H2-O) inhibits DM (H2-M) function; this inhibition is pH-dependent. As a consequence, DO restrains presentation of exogenous antigens delivered through nonreceptor-mediated mechanisms; in addition, DO alters the peptide repertoire that is associated with cell-surface class II molecules. The biological function of DO remains obscure, partially because of the lack of striking phenotypes in the H2-O knockout mice. Results from recent studies indicate that DO expression in B cells is dynamic, and highly regulated during B-cell development and B-cell activation, suggesting that the physiological role of DO is to tailor the antigen presentation function of the B-lineage cells to meet their primary function at each stage of B-cell development and maturation. Further investigations are needed in this direction.

Animals↗

PubMed2003

HLA-DO. A useful marker to distinguish florid follicular hyperplasia from follicular lymphoma by flow cytometry.

HLA-DO expression is regulated during B-cell development and activation. To determine whether the level of HLA-DO expression is a helpful marker in the differential diagnosis between florid follicular hyperplasia and follicular lymphoma, we analyzed single-cell suspensions from 29 lymph node specimens by 4-color flow cytometry. Of the 29 specimens, 7 were from patients with florid follicular hyperplasia, in which the clonality of the germinal center B cells (GCBCs) was indeterminate by flow cytometric immunophenotyping. The remaining 22 cases were follicular lymphomas; neoplastic cells in 2 of these cases lacked expression of surface immunoglobulin light chains. The level of HLA-DO expression in the reactive CD10+ GCBCs in florid follicular hyperplasia was markedly down-regulated compared with the CD10- polytypic B cells of the same specimens. In contrast, the level of HLA-DO expression in the CD10+ neoplastic cells in all cases of follicular lymphomas was similar to that of the CD10- polytypic B cells, thus higher than the reactive CD10+ GCBCs. This difference was confirmed by immunohistochemical staining. Our results suggest that HLA-DO is a useful marker to differentiate florid follicular hyperplasia from follicular lymphoma by flow cytometry, particularly when clonality of the CD10+ B cells is in question.

B-Lymphocytes↗

PubMed2002

Regulated expression of human histocompatibility leukocyte antigen (HLA)-DO during antigen-dependent and antigen-independent phases of B cell development.

Human histocompatibility leukocyte antigen (HLA)-DO, a lysosomal resident major histocompatibility complex class II molecule expressed in B cells, has previously been shown to be a negative regulator of HLA-DM peptide loading function. We analyze the expression of DO in human peripheral blood, lymph node, tonsil, and bone marrow to determine if DO expression is modulated in the physiological setting. B cells, but not monocytes or monocyte-derived dendritic cells, are observed to express this protein. Preclearing experiments demonstrate that approximately 50% of HLA-DM is bound to DO in peripheral blood B cells. HLA-DM and HLA-DR expression is demonstrated early in B cell development, beginning at the pro-B stage in adult human bone marrow. In contrast, DO expression is initiated only after B cell development is complete. In all situations, there is a striking correlation between intracellular DO expression and cell surface class II-associated invariant chain peptide expression, which suggests that DO substantially inhibits DM function in primary human B cells. We report that the expression of DO is markedly downmodulated in human germinal center B cells. Modulation of DO expression may provide a mechanism to regulate peptide loading activity and antigen presentation by B cells during the development of humoral immune responses.

Adult↗

PubMed2002

Class II transactivator is required for maximal expression of HLA-DOB in B cells.

HLA-DO, encoded by the HLA-DOA and HLA-DOB genes, has been shown to function as a modulator of Ag presentation. DNA microarray comparisons between B cells wild-type and mutant for the master regulator of MHC class II transcription, class II transactivator (CIITA), identified HLA-DOA and HLA-DOB as being up-regulated by CIITA. Although HLA-DOA had been shown previously to be regulated by CIITA, HLA-DOB expression was suggested to be independent of CIITA. A series of assays including quantitative RT-PCR, promoter-reporter assays, chromatin immunoprecipitations, and intracellular staining were performed to corroborate the DNA microarray analysis. The combined data demonstrate that HLA-DOB levels are increased by CIITA, and that this difference has an impact on the overall level of HLA-DO expression. Additionally, unlike the classical MHC class II genes, HLA-DOB expression was present in the absence of CIITA, indicating that additional factors mediate HLA-DOB expression in B cells.

Amino Acid Sequence↗

PubMed2002

[Studies on immunocompetent constituents of Patrinia scabra Bunge].

Five compounds were isolated from the roots of Patrinia scabra Bunge separated and purified on sillica gel column chromatography. Their structures were elucidated on the physico-chemical properties and spectral data as lariciresinol(I), syringaresinol(II), scopoletin(III), quercetin(IV), ferulaic acid(V). All compounds were obtained from P. scabra for the first time. In vitro biological test of these compounds showed that syringaresinol was able to stimulate T and B lymphocyte proliferation.

B-Lymphocytes↗