C5a anaphylatoxin as a product of complement activation up-regulates the complement inhibitory factor H in rat Kupffer cells.
The 155-kDa complement regulator factor H (FH) is the predominant soluble regulatory protein of the complement system. It acts as a cofactor for the factor I-mediated conversion of the component C3b to iC3b, competes with factor B for a binding site on C3b and C3(H2O) and promotes the dissociation of the C3bBb complex. The primary site of synthesis is the liver, i.e. FH-specific mRNA and protein were identified in both hepatocytes (HC) and Kupffer cells (KC). Previous studies in rat primary HC and KC had shown that the proinflammatory cytokine IFN-gamma influences the balance between activation and inhibition of the complement system through up-regulation of the inhibitory FH. In this study we show that C5a, as a product of complement activation, stimulates the expression of FH-specific mRNA and protein in KC and thus induces a negative feedback. Quantitative-competitive RT-PCR showed an approximate threefold C5a-induced up-regulation of FH. ELISA analyses revealed a corresponding increase in FH protein in the supernatants of KC. The up-regulation of FH was completely inhibited by the C5a-blocking monoclonal antibody 6-9F. Furthermore, an involvement of LPS and IFN-gamma was excluded, which strongly indicates a direct effect of C5a on the expression of FH in KC.
Schlaf
Gerald
G
Department of Immunology, Georg-August University, Göttingen, Germany. gschlaf1@gwdg.de
Nitzki
Frauke
F
Heine
Ines
I
Hardeland
Rüdiger
R
Schieferdecker
Henrike L
HL
Götze
Otto
O
D000818:Animals; D019138:Antibodies, Blocking / Q000276:immunology; D015152:Blotting, Northern; D003167:Complement Activation / Q000276:immunology*; D015936:Complement C5a / Q000276:immunology*; D017242:Complement Factor H / Q000096:biosynthesis / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D007728:Kupffer Cells / Q000276:immunology / Q000378:metabolism; D008099:Liver / Q000276:immunology; D008297:Male; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015854:Up-Regulation / Q000276:immunology; D048809:alpha-N-Acetylgalactosaminidase / Q000276:immunology
D019138:Antibodies, Blocking; D012333:RNA, Messenger; D015936:Complement C5a; D017242:Complement Factor H; D048809:alpha-N-Acetylgalactosaminidase