EIL-4 protects the B-cell lymphoma cell line CH31 from anti-lgM-induced growth arrest and apoptosis： contribution of the PI-3 kinase/AKT pathway

Interleukin-4 （IL-4） promotes lymphocyte survival and protects primary lymphomas from apoptosls. Previous studies reported differential requirements for the signal transducer and activator of transcription 6 （STAT6） and IRS2/phosphati-dylinositol 3 kinase （PI-3K） signaling pathways in mediating the IL-4-induced protection from Fas-mediated apoptosis. In this study, we characterized IL-4-activated signals that suppress anti-IgM-mediated apoptosis and growth arrest of CH31, a model B-cell lymphoma line. In CH31, anti-IgM treatment leads to the loss of mitochondrial membrane poten-tial, phospho-Akt, phospho-CDK2, and c-myc protein. These losses are followed by massive induction of p27^Kip1 protein expression, cell cycle arrest, and apoptosis. Strikingly, IL-4 treatment prevented or reversed these changes. Furthermore, IL-4 suppressed the activation of caspases 9 and 3, and, in contrast to previous reports, induced the phosphorylation （de-activation） of BAD. IL-4 treatment also induced expression of BclxL, a STAT6-dependent gene. Pharmacologic inhibitors and dominant inhibitory forms of PI-3K and Akt abrogated the anti-apoptotic function of IL-4. These results suggest that the IL-4 receptor activates several signaling pathways, with the Akt pathway playing a major role in suppression of the apoptotic program activated by anti-IgM.

Regulation of cytokine production during phagocytosis of apoptotic cells

Loss of self-tolerance and expansion of auto-reactive lymphocytes are the basis for autoimmunity. Apoptosis and the rapid clearance of apoptotic cells by phagocytes usually occur as coordinated processes that ensure regulated cellularity and stress response with non-pathological outcomes. Defects in clearance of apoptotic ceils would contribute to the generation of self-reactive lymphocytes, which drive autoimmune disorders such as rheumatoid arthritis （RA） and systemic lupus erythematosus （SLE）. The IL-12 family of cytokines （IL-12, IL-23, and IL-27） and IL-10 are produced by phagocytic macrophages and play critical roles in the regulation of antigen-presenting cells （APCs） and effector lymphocytes during an immune response to pathogens. Inappropriate expression of these cytokines and their dysregulated activities have been strongly implicated in the pathogenesis of several autoimmune diseases. The production of pro- and anti-inflammatory cytokines by phagocytic APCs is delicately regulated during the ingestion of apoptotic cells as part of an intrinsic mechanism to prevent inflammatory autoimmune reactions. How apoptotic cell-derived signals regulate cytokine production is poorly understood. A recent study by our group demonstrated that phagocytosis of apoptotic cells by activated macrophages results in strong inhibition of IL-12 p35 gene expression by activating a novel transcription repressor, which we named GC-binding protein （GC-BP）, through tyrosine dephosphorylation. We are also beginning to understand the molecular mechanisms underlying apoptotic cell-triggered production of IL-10 by phagocytes. These studies will help to elucidate some novel immune regulatory mechanisms and explore the regulation of immune responses to autoantigens with potentials to discover new therapeutic targets for the treatment of autoimmune disorders.

Localization and characterization of the hypothetical protein CT440 in Chlamydia trachomatis-infected cells

The inclusion membrane proteins play potentially important roles in chlamydial biology and pathogenesis.Here we localized and characterized the hypothetical protein CT440 in Chlamydia trachomatis-infected cells.The open reading frame(ORF) encoding the CT440 protein from the C.trachomatis serovar D genome was cloned into the prokaryotic expression vector pGEX-6p and expressed as a glutathione-S-transferase(GST) fusion protein in E.coli XL1-Blue.The CT440 fusion protein was used to immunize mice to raise antigen-specific antibody.After verification by Western blot and immunofluorescence assay(IFA),the specific antibody was used to localize the endogenous CT440 protein and to detect its expression pattern in Chlamydia-infected cells.Cytosolic expression of CT440 in HeLa cells was also carried out to evaluate the effect of the CT440 protein on the subsequent chlamydial infection.The results showed that the hypothetical protein CT440 was localized in the C.trachomatis inclusion membrane,and was detectable 12 h after chlamydial infection.Expression of CT440 in the cytoplasm did not inhibit the subsequent chlamydial infection.In summary,we have identified a new inclusion membrane protein that may be an important candidate for understanding C.trachomatis pathogenesis.