Tetraspanin CD9: A Key Regulator of Cell Adhesion in the Immune System.

The tetraspanin CD9 is expressed by all the major subsets of leukocytes (B cells, CD4+ T cells, CD8+ T cells, natural killer cells, granulocytes, monocytes and macrophages, and immature and mature dendritic cells) and also at a high level by endothelial cells. As a typical member of the tetraspanin superfamily, a prominent feature of CD9 is its propensity to engage in a multitude of interactions with other tetraspanins as well as with different transmembrane and intracellular proteins within the context of defined membranal domains termed tetraspanin-enriched microdomains (TEMs). Through these associations, CD9 influences many cellular activities in the different subtypes of leukocytes and in endothelial cells, including intracellular signaling, proliferation, activation, survival, migration, invasion, adhesion, and diapedesis. Several excellent reviews have already covered the topic of how tetraspanins, including CD9, regulate these cellular processes in the different cells of the immune system. In this mini-review, however, we will focus particularly on describing and discussing the regulatory effects exerted by CD9 on different adhesion molecules that play pivotal roles in the physiology of leukocytes and endothelial cells, with a particular emphasis in the regulation of adhesion molecules of the integrin and immunoglobulin superfamilies.

Elevated expression of CX3C chemokine receptor 1 mediates recruitment of T cells into bone marrow of patients with acquired aplastic anaemia.

OBJECTIVE: Acquired aplastic anaemia (AA) is a T-cell-mediated, organ-specific autoimmune disease characterized by haematopoietic stem cell destruction in the bone marrow. The exact molecular mechanism of T-cell trafficking into the bone marrow is unclear in AA. Very late activation antigen-4 (VLA-4) and CX3C chemokine receptor 1 (CX3CR1) play active roles in many autoimmune diseases. Therefore, we investigated whether VLA-4 and CX3CR1 also contribute to T-cell migration into the bone marrow in acquired AA. DESIGN, SETTING AND SUBJECTS: Expression levels of CX3CR1 and VLA-4 and their ligands [fractalkine (CX3CL1) and vascular cell adhesion molecule-1 (VCAM-1)] were examined in 63 patients with AA and 21 healthy control subjects. T-cell chemotaxis and adhesion were analysed in 17 patients with severe AA. We also prospectively evaluated the expression pattern of CX3CR1 during treatment with antithymocyte globulin plus cyclosporine in 11 patients with severe AA. RESULTS: The proportion of peripheral and bone marrow CD4(+) and CD8(+) T cells expressing CX3CR1 and the level of CX3CL1 was increased in patients with AA. However, there was no significant difference in VLA-4 expression or VCAM-1 levels. Functional studies demonstrated that chemotaxis towards autologous bone marrow plasma or soluble CX3CL1 was significantly higher in T cells from AA patients and could be blocked by CX3CR1 inhibitors. CX3CR1-mediated T-cell adhesion was also upregulated in these patients. The expression of CX3CR1 was associated with the efficacy of immunosuppressive therapy. CONCLUSION: The present findings demonstrate that CX3CR1 plays a pivotal role in recruitment of T cells into the bone marrow in acquired AA and is a potential therapeutic target for treatment of this disorder.

Computer-aided identification of novel protein targets of bisphenol A.

The xenoestrogen bisphenol A (2,2-bis-(p-hydroxyphenyl)-2-propane, BPA) is a known endocrine-disrupting chemical used in the fabrication of plastics, resins and flame retardants, that can be found throughout the environment and in numerous every day products. Human exposure to this chemical is extensive and generally occurs via oral route because it leaches from the food and beverage containers that contain it. Although most of the effects related to BPA exposure have been linked to the activation of the estrogen receptor (ER), the mechanisms of the interaction of BPA with protein targets different from ER are still unknown. Therefore, the objective of this work was to use a bioinformatics approach to identify possible new targets for BPA. Docking studies were performed between the optimized structure of BPA and 271 proteins related to different biochemical processes, as selected by text-mining. Refinement docking experiments and conformational analyses were carried out using LigandScout 3.0 for the proteins selected through the affinity ranking (lower than -8.0kcal/mol). Several proteins including ERR gamma (-9.9kcal/mol), and dual specificity protein kinases CLK-4 (-9.5kcal/mol), CLK-1 (-9.1kcal/mol) and CLK-2 (-9.0kcal/mol) presented great in silico binding affinities for BPA. The interactions between those proteins and BPA were mostly hydrophobic with the presence of some hydrogen bonds formed by leucine and asparagine residues. Therefore, this study suggests that this endocrine disruptor may have other targets different from the ER.

Inhibitory effect of berberine on the activation and proliferation of T lymphocytes / 中国病理生理杂志

AIM: To investigate the effect of berberine (Ber) on the activation and proliferation of T lymphocytes and its mechanism of action. METHODS: Whole peripheral blood from normal subjects was stimulated with phytohemagglutinin (PHA) or phorbol ester (PDB) plus ionomycin (Ion) and the expression levels of CD69 and CD25 were evaluated with flow cytometry after the staining with appropriate fluorescent monoclonal antibody. The distribution of cell cycles was analyzed by propidium iodide staining and dead cells by 7-aminoactinomycin live staining. RESULTS: 100 ?mol/L and 50 ?mol/L of Ber had significant inhibition of the expression of CD69 on T cells stimulated with PDB plus Ion or PHA, while effect of 25 ?mol/L Ber was not significant. And as time of action extended, the extent of inhibition decreased. For the expression of CD25, Ber at the concentrations as above all exerted significant inhibitory effect in a dose-dependent manner. Moreover, Ber could block lymphocytes cell cycle progression from G_0/G_1 phase to S and G_2/M phase without phase specificity. Besides, live staining analysis revealed that Ber did not have significant cytotoxicity on lymphocytes. CONCLUSIONS: Ber significantly inhibits the expression of early and mid activation antigens of T cells and also blocks the progression of lymphocytes cell cycles. These results suggest that Ber exerts immunosuppression effect through inhibiting the activation and proliferation of T cells.

5C5-a novel antigen restrictedly exprossed on human activated B cells / 中国免疫学杂志

Using a human activated B cell line 3D5 in immunization of mouse and as targets in screening, a hybridoma producing McAb 5C5 has been established. The antigen recognized by the McAb starts its expression on low dose anti-?-activated B cells at their G_1 phase at the 10th hour. The number of 5C5~+ cells increases with time. At the stimulation of PWM, the number of 5C5~+ cells in PBMNC also increases with time, and peaks on day 3 to 4, then docreases and comes to the background on day 7.5C5 antigen is positive on the B cell lines which can not be induced to differentiate to Ig-secre-ting cells (ISC), but negative on those being able to be driven to differentiate to ISC by BCDF. All the data indicate that 5C5 expresses at the early and mid stages, but disappears at the terminal stage of B cell activation and differentiation. 5C5 antigen does not expresses on resting B cells, resting T cells, PHA-activated T cells, monocytes, neutrophils, and the T cell and myeloid cell lines detected. Electrophoresis under both the nonreducing and reducing state for the ~(125)I-label led antigen immunoprecipi tated with McAb 5C5 shows a single band with a molecular weight of 52000, suggesting that 5C5 be a single chain cell surface protein. Since the MW of 5C5 is different from that of those B cell activation antigens reported in literature, and since ins specific expression on cell lines, 5C5 antigen might be a novel B eel I-restricted activation antigen.

Molecular cloning of mouse CD226(PTA1) and its isoforms / 中国免疫学杂志

Objective:To clone mouse CD226(platelet and T cell activation antigen1,PTA1).Methods:Specific primers were designed and sythesized according to the EST sequence from GenBank,which had 51% homology to human CD226 on the amino acid level.And then,the cDNA of mouse CD226 was cloned from the thymus of 4 week old BALB/c mouse by using RACE technique.Results:The length of mouse CD226 cDNA is 2 223 bp,with the open reading frame(ORF) of 1 002 bp,encoding 333 amino acids,which is 3 amino acids shorter than its counterpart in human.The mouse CD226 belongs to IgSF,and shares 53% homology with human PTA1 on amino acid level.Besides,three isoforms of mouse PTA1 were also cloned at the mean time.Conclusion:The molecular cloning of mouse PTA1 lays the foundation for the in vivo studies on the biological function of this molecule,as well as the studies of this molecule in gene knockout mouse and transgenic mouse.