title: A novel, complement factor H-related regulatory protein expressed on the surface of human B cell lines.
abstract: Complement regulatory proteins present on the surface of various mammalian cells play an important role in controlling homologous lysis, by interacting with C3 (and usually C4). These proteins have a similar structural motif ("short consensus repeat") (Reid, K.B.M., Bentley, R.D., Campbell, R.D., Chung, L.P., Sim, R.B., Kristensen, T. and Tack, B.F., Immunol. Today 1986. 7:230), and the genes encoding them are members of the family of regulators of complement activation. Here we describe a hitherto unknown member of this family, a molecule expressed by B lymphoblastoid cells. This protein is recognized by polyclonal antibodies to factor H and by MAH4, a monoclonal antibody reacting with the N-terminal portion of factor H. The cell surface protein is built up of two disulfide-linked chains of approximately 68 and 75 kDa. Biosynthetic labeling studies confirmed that it is synthesized by B cells only, but not by the investigated lines of other origin. When tested for its functional activity, this molecule was shown to act as cofactor for factor I-mediated cleavage of fluid-phase C3b to C3bi. The protein appears to be encoded by a 3.5-kb mRNA, hybridizing with a cDNA probe coding for the N-terminal portion of factor H. Due to its cross-reactivity with anti-H antibodies, cofactor activity for factor I and hybridization with factor H cDNA, despite its two-chain composition, it is considered a factor H-like protein.
authors.affiliation: Department of Immunology, L. Eötvös University, Göd, Hungary.
authors.forename: A
authors.initials: A
authors.lastname: Erdei
authors.forename: N
authors.initials: N
authors.lastname: Julen
authors.forename: P
authors.initials: P
authors.lastname: Marschang
authors.forename: E
authors.initials: E
authors.lastname: Feifel
authors.forename: K
authors.initials: K
authors.lastname: Kerekes
authors.forename: M P
authors.initials: MP
authors.lastname: Dierich
mesh_terms: D001402:B-Lymphocytes / Q000737:chemistry*; D015152:Blotting, Northern; D002460:Cell Line; D017242:Complement Factor H / Q000032:analysis* / Q000096:biosynthesis / Q000276:immunology; D006801:Humans; D011233:Precipitin Tests; D012333:RNA, Messenger / Q000032:analysis
chemical_list: C493495:CFH protein, human; D012333:RNA, Messenger; D017242:Complement Factor H