Myeloid-derived suppressor cells ( MDSC) are a bone marrow-derived heterogeneous cell population with immuno-suppressive activity.Although there is convincing evidence that autoimmune diseases are associated with MDSC expansion ,controversies remained regarding the role of MDSCs in controlling autoimmune responses .Recent studies have shown that the expansion of MDSCs , which are capable of inhibiting effector cell function in vitro ,does not always lead to alleviation of autoimmune diseases ,and in some ca-ses paradoxically exacerbates the disease progression .This review summarizes recent insights into the role of MDSCs in the development of autoimmune responses and the potential of using MDSCs for the treatment of autoimmune diseases .

Objective To establish an aging model of mesenchymal stem cells (MSCs) and to investigate aging related biological mechanism for the purpose of studying the senesence of MSCs .Methods MSCs were separated and purified from human placenta, and the cells of the third passage(P3-MSCs) were cultured in the medium for 2 hours, then 100,200 and 300 μmol/L hydrogen peroxide ( H2 O2 ) was added to the cells for 2 hours to establish the MSCs aging model in vitro. Biological characteristics of aging MSCs were evaluated by cell cycle assay and senescence associated β-galactosidase staining.The expression of p16,p21 and p53 genes was further measured using quantitative real-time PCR (RT-PCR).Re-sults Compared with the control , the number of MSCs treated with 200μmol/L H2 O2 for 2 hours was significantly decreased and the cells displayed less adipogenic ,osteogenic and chondrogenic differentiation .Moreover ,after exposure to 200 μmol/L H2 O2 , the majority of the cells were in the G 0/G1 phase as showed by cell cycle analysis .The percentage of senescence-associated β-galactosidase-positive cells was increased , and the expression of p 16 , p21 and p53 mRNA and protein was significantly increased.Conclusion The results of this study has demonstrated that the H 2 O2 (200 μmol/L) can be used to establish the aging model of MSCs in vitro, and the cellular phenotypic alteration may attribute to the cell cycle associated gene expression (p16, p21, and p53).

In order to study the biological function of pig BST-2 gene,the BST-2 gene was amplified with specific primers from porcine kidney tissue,and molecular characterization of BST-2 nuclectide and amino acid sequence were analyzed with bioinformatics tools and online server.Then the prokaryotic expression and tissue expression profile analysis was carried out.The results showed that the full length of pig BST-2 gene was 851 bp and contained 23 bp of 5'-UTR,294 bp of 3'-UTR and 534 bp of CDS and the gene encoded 177 aa.Amino acid sequence analysis of pig BST-2 protein showed 46.1％ identity with gorilla gorilla,41.7％ with cricetulus griseus,39.5％ with mus musculus,35.4％ with equus asinus,42.0％ with felis catus,40.5％ with bos mutus,44.4％ with macaca mulatta,38.7％ with ovis aries and 46.8％ with homo sapiens.BST-2 protein contained 2 transmembrane structure (27-49 aa and 154-176 aa),2 glycosylation sites and 14 potential phosphorylation sites including ATM,CK Ⅱ,PKA,PKC binding sites.The pig BST-2 protein was expressed in Vero cells after translated the recombinant plasmid FLAG-BST-2.Semiquantitative PCR results showed that BST-2 gene was expressed in all the tissues,especially in lymph nodes,thymus,tonsils,spleen,large intestine and small intestine.This study provide a foundation for further understanding the antiviral mechanism of pig BST-2 protein.

BACKGROUND:Placenta is a valuable source of mesenchymal stem cels for stem cel therapy and future application in the field of regenerative medicine. However, conventional methods cannot acquire a large amount of purified human placenta-derived mesenchymal stem cels. Here, we present a new method for isolating human placenta-derived mesenchymal stem cels suitable for banking strategies and for future clinical applications. OBJECTIVE:To analyze the biological characteristics of human placenta-derived mesenchymal stem cels cultured by tissue dissociating and colagenase digestion. METHODS: Human placenta-derived mesenchymal stem cels were obtained from human placenta by tissue dissociating and colagenase digestion method. Immunophenotype was analyzed by flow cytometry. Growth curve was determined by MTT assay, and differentiation ability was evaluated byin vitro adipogenic, osteogenic and chondrogenic induction as wel. RESULTS AND CONCLUSION:Human placenta-derived mesenchymal stem cels could be passaged stablyin vitro. Furthermore, the cels expressed CD73, CD90, CD105, but were negative for the markers of CD11b, CD19, CD34, CD45, and HLA-DR. Human placenta-derived mesenchymal stem cels proliferated actively and began to grow logarithmicaly at days 3-5 folowed by a plateau period at day 6. In addition, the isolated cels could be induced into adipocytes, osteocytes, chondrocytesin vitro. In a word, the results of this study demonstrated that the tissue dissociating and colagenase digestion method is an efficient method for obtaining a large amount of human placenta-derived mesenchymal stem cels that can be stably cultured in vitro and have strong proliferative ability.

BACKGROUND:Fisher-Lewis rat kidney transplant models are the international common chronic renal alograft rejection models, but their application is greatly limited because of difficulty in model preparation and high costs. OBJECTIVE:To explore a new method of establishing SD-Wistar rat models of chronic renal alograft rejection. METHODS: Fifty-six pairs of SD-Wistar rats were subjected to left kidney orthotopic transplantation. The right kidneys of the recipients were intact and used as internal controls. 23 rat recipients were randomly divided into model group (n=15) and control group (n=8). The rats in the model group were injected with cyclosporine microemulsion for 10 days (2 mg/kg/day,i.p.) after kidney transplantation. The rats in the control group were not treated with immunosuppressive therapy. RESULTS AND CONCLUSION:The irreversible acute rejection occurred in al the transplanted kidneys of rats in the control group within 4 weeks, leading to the necrosis of transplanted kidney. Moderate inflammatory cel infiltration appeared in the transplanted kidneys of rats in the model group at 4, 8 and 12 weeks after transplantation. Typical histopathological changes of chronic rejection were observed within 12 weeks after transplantation. The Banff total scores were increased with time after transplantation. Al these histopathological changes were not observed in the intact right kidneys of rat recipients in both groups. The valey value of 

Objective:To analyze the contagiousness and secondary attack rate of 2019 novel coronavirus in cluster epidemics in Guangzhou and provide evidence for the prevention and control of COVID-19.Methods:All the individuals identified to be infected with 2019-nCoV in Guangzhou, including confirmed cases and asymptomatic cases, were included and classified as imported cases and local cases. The first case of each cluster epidemic was defined as index case, and the number of subsequent infections was calculated to evaluate the contagiousness and secondary attack rate of 2019 novel coronavirus in the shortest incubation period of 1-3 days.Results:As of 18 February, 2020, a total of 349 cases of 2019-nCoV infection, including 339 confirmed cases (97.13 %) and 10 asymptomatic cases (2.87 %) were reported in Guangzhou. There were 68 clusters involving 217 2019-nCoV infection cases (210 confirmed cases and 7 asymptomatic cases). The median number of subsequent infections caused by an index case in a cluster epidemic was 3, among which 2 were confirmed cases and 1 was asymptomatic cases, respectively. The average number of contagiousness was 2.18 in shorted incubation period of 1-3 days (The average number of infected cases were 2.18 cases by the index case in a cluster epidemic), the average infection number in family members was 1.86, and the infection ratio of family member transmission was 85.32 % (1.86/2.18). The secondary attack rate in close contacts with shortest incubation period of 1-3 days was 17.12 %-18.99 %, the secondary attack rate in family members was 46.11 %-49.56 %. Conclusions:The cluster epidemic of COVID-19 in Guangzhou mainly occurred in families, the contagiousness was high. It is necessary to strengthen the prevention and control to reduce the community transmission of COVID-19.

Objective:To investigate the diagnosis and treatment significance of invasive and noninvasive operation for ventilator?as?sociated pneumonia ( VAP ) . Methods:A total of 80 cases of VAP suspected patients who had received mechanical ventilation at least 48 hours in ICU from Jun 2014 to Mar 2015 were enrolled. Patients were randomly divided into four groups including noninvasive operation group ( F) , invasive operation group ( Q) , mix group 1 ( H1) and mix group 2 ( H2) . VAP diagnosis rate between groups as well as living time, antibiotic use time, survival rate, calcitonin levels and APACHE II score, oxygenation index were analyzed. Results:Specimen from invasive operation had higher specimens to cultivate positive rate than that from noninvasive operation ( P<0?05), but there was no statistic significant difference in VAP diagnosis rate between two methods (P>0?05). Conclusion:Noninva?sive operation collecting samples for VAP diagnosis is also accurate as invasive one. Collecting specimens from sputum suction tube in the clinical treatment on airway suction is a low cost and simple noninvasive operation.