title: A targeted disruption of the murine complement factor B gene resulting in loss of expression of three genes in close proximity, factor B, C2, and D17H6S45.
abstract: Factor B is a serine protease, essential for the function of the alternative pathway of complement activation. To study further the importance of the alternative pathway of complement activation in vivo and to help elucidate any additional functions of factor B or its activation fragments we developed, by homologous recombination in embryonic stem cells, mice with a disrupted factor B gene. Factor B-deficient mice produced no detectable factor B mRNA or protein and had no detectable factor B enzymatic activity or alternative pathway function in their serum. Further studies revealed that the two adjacent genes, complement component C2 and D17H6S45, had been down regulated as a result of the disruption. The down-regulation of C2 gene expression was sufficient to cause a complete loss of classical pathway function as determined by the failure of sera from the deficient mice to opsonize antibody-sensitized sheep erythrocytes and by impairment of immune complex processing in vivo. The resulting mouse is deficient in both factor B and C2, and hence the alternative and classical pathways of complement activation, and adds to the repertoire of models for studying the in vivo role of complement in the immune system.
authors.affiliation: Rheumatology Section, Imperial College School of Medicine, Hammersmith Hospital, London, United Kingdom.
authors.forename: P R
authors.initials: PR
authors.lastname: Taylor
authors.forename: J T
authors.initials: JT
authors.lastname: Nash
authors.forename: E
authors.initials: E
authors.lastname: Theodoridis
authors.forename: A E
authors.initials: AE
authors.lastname: Bygrave
authors.forename: M J
authors.initials: MJ
authors.lastname: Walport
authors.forename: M
authors.initials: M
authors.lastname: Botto
mesh_terms: D000818:Animals; D003167:Complement Activation; D003175:Complement C2 / Q000235:genetics*; D011415:Complement Factor B / Q000235:genetics*; D003170:Complement Pathway, Alternative; D015536:Down-Regulation; D015870:Gene Expression; D051379:Mice; D008810:Mice, Inbred C57BL; D009687:Nuclear Proteins / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D003175:Complement C2; D009687:Nuclear Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; C498268:Rdbp protein, mouse; D011415:Complement Factor B