Toll-like receptors (TLRs), a large family consisting of at least 10 members, are evolutionarily conserved to recognize pathogen-associated molecular patterns (PAMPs). TLRs activation not only initiates innate immunity, but also regulates enhance antigen-specific acquired immunity, and thus associates innate and adaptive immunity. In recent years, studies on the TLRs signaling, especially their negative regulation, rapidly progressed. TLRs signaling pathway and their roles in regulating immune responses against invading pathogens were reviewed.

Toll-like receptors (TLRs) are key mediators of both innate and adaptive immunity by recognizing and eliciting responses to invading pathogens. The activation of TLRs must be stringently controlled in order to avoid exaggerated expression of signaling components as well as pro-inflammatory cytokines that can devastate the host,resulting in chronic inflammatory diseases,autoimmune disorders and aid in the pathogenesis of TLR-associated diseases. Therefore,it is essential that negative regulators act at multiple levels within TLR signaling cascades in order to synchronize the activation and negative regulation of signal transduction to limit potentially harmful immunological consequences. A summary of the various mechanisms employed by negative regulators of TLRs signaling to ensure the appropriate modulation of both immune and inflammatory responses was provided.

The changes of the growth characteristics and surface ultrastructure during longterm passages of Wg3h cells that have been transfected with PSV_2-neo (Wg3h-neo) were studied. The results showed that the growth and DNA synthesis rate were evidently higher in the transfected cells than in the parental wg3h cells. The saturation of the transfected cell growth density was also increased, but neither the parental and transfected cells formed cell colony in soft agar medium nor tumor growth in nude mice. There was no significant differences in morphology between the two cell types under light microscopy, however much more microvilli were seen on the transfected cell surface under scanning electron microscopy. Southern blot hybridization analysis indicated that the PSV_2-neo plasmids were integrated into the genome of the target cells. Our results demonstrated that the transfected cells remained as nonmalignant cells although some changes of their growth characteristics and surface ultrastructure appeared.

OBJECTIVETo investigate the roles of mouse erythroid differentiation and denucleation factor (MEDDF), a novel factor cloned in our laboratory recently, in erythroid terminal differentiation.

METHODSMouse erythroleukemia (MEL) cells were transfected with eukaryotic expression plasmid pcDNA-MEDDF. Then we investigated the changes on characteristics of cell growth by analyzing cells growth rate, mitotic index and colony-forming rate in semi-solid medium. The expressions of c-myc and beta-globin genes were analysed by semi-quantitative RT-PCR.

RESULTSMEL cells transfected with pcDNA-MEDDF showed significant lower growth rate, mitotic index, and colony-forming rate in semi-solid medium (P<0.01). The percentage of benzidine-positive cells was 32.8% after transfection. The expression of beta-globin in cells transfected with pcDNA-MEDDF was 3.43 times higher than that of control (MEL transfected with blank vector, pcDNA3.1), and the expression of c-myc decreased by 66.3%.

CONCLUSIONSMEDDF can induce differentiation of MEL cell and suppress its malignancy.

Activins ; genetics ; pharmacology ; Animals ; Cell Differentiation ; drug effects ; Cell Division ; drug effects ; Friend murine leukemia virus ; Globins ; biosynthesis ; genetics ; Inhibin-beta Subunits ; genetics ; pharmacology ; Leukemia, Erythroblastic, Acute ; metabolism ; pathology ; Mice ; Proto-Oncogene Proteins c-myc ; biosynthesis ; genetics ; RNA, Messenger ; biosynthesis ; Transfection ; Tumor Cells, Cultured