Research On CD47 In Autoimmune Nephritis And The Role Of SIRPa Expression On Phagocytosis Under Inflammatory Conditions

The thesis consists of two parts,focusing on the research on the role of CD47 in autoimmune nephritis,the role of SIRPa expression on phagocytosis under inflammatory conditions.1.The role of CD47 in autoimmune nephritisCD47,a self-recognition marker,plays an important role in both innate and adaptive immune response.To explore the potential role of CD47 in activation of autoreactive T and B cells and the production of autoantibodies in autoimmune disease such as systemic lupus erythematosus(SLE),we generated CD47-knockout Faslpr(CD47-/--Faslpr)mice and examined them for histopathologic changes in the kidneys,cumulative survival rates,proteinuria,extent of splenomegaly and autoantibodies,serum chemistry and immunologic parameters.In comparison with Faslpr mice,CD47-/--Faslpr mice exhibited a prolonged lifespan,with no apparent signs of autoimmune nephritis,including glomerular cell proliferation,acute tubular atrophy and vacuolization.CD47-/--Faslpr mice had lower level of proteinuria and less pronounced splenomegaly compared to the age-matched Faslpr mice.Serum levels of antinuclear antibodies(ANAs)and anti-double-stranded DNA(anti-dsDNA)antibodies were significantly lower in CD47-/--Faslpr mice than those in Faslpr mice.CD47 deficiency also resulted in a significant reduction of IgG but not IgM level in the kidneys from Faslpr mice.The deposition of C3 and Clq in the glomeruli of CD47-/--Faslpr mice was decreased compared to that in Faslpr mice.The mechanistic studies further suggested that CD47 deficiency might impair the antigenic challenge-induced production of mouse high affinity IgG but not IgM through reducing T follicular cell production,which results in an impaired formation of germinal centers in lymph tissue.In conclusion,our results demonstrate for the first time that CD47 deficiency ameliorates lupus nephritis in Falpr mice via suppressing IgG autoantibody production.2.The role of SIRPa expression on phagocytosis under inflammatory conditionsAs a member of immunoglobulin superfamily(IgSF),signal regulatory protein A(SIRPa)is a receptor-like signaling protein.Accumulating evidences indicate SIRPa plays a very important role in cell differentiation,proliferation,migration and apoptosis.Previous study has shown that LPS induce reduction of SIRPa through regulation of miR-17,miR-20a,and miR-106a.In the meantime,we also found SIRPa protein levels in macrophages were increased after stimulated by IL-17A.Thus,we went ahead to test if other cytokines have role in SIRPa expression and if their regulations affect macrophage function.In this dissertation,we purpose to investigate the regulation of SIRPa by other cytokines and its effects on the phagocytosis of self-cells and cancer cells.We detected the protein level of SIRPa in macrophages after treatment by IL-1β,IL-6,IFNγ,IL-4,IL-10,IL-17A and TNFa using LPS as a positive control.We found that SIRPα protein level were regulated by theses cytokines through MAPK,NFκB and JAK-STAT pathway.MiR-17,miR-20a and miR-106a regulated SIRPa protein at the posttranscriptional level independent of c-myc.C-myc was identified to regulate transcriptional level of SIRPa in the macrophage as an enhancer.In the meantime,SIRPα protein level had no effect on the phagocytosis of E.coli,Zymosan and apoptotic cells by macrophage,and the ROS production.However,decreased SIRPa enhanced the phagocytosis of self red blood cells and MC3 8 tumor cells and increase the Fc-mediated tumor cells clearence.In summary,we first regulated SIRPa protein level by cytokines,identified the signaling pathway,and conducted more in-depth research on the function of SIRPa regulation on macrophage.We improved the elimination of CD47+RBC and tumor cells by decreased SIRPα on the membrane of macrophage.