title: The leukocyte integrin p150,95 (CD11c/CD18) as a receptor for iC3b. Activation by a heterologous beta subunit and localization of a ligand recognition site to the I domain.
abstract: p150,95 is a member of the leukocyte integrin family of adhesion proteins. Compared with LFA-1 and Mac-1, p150,95 is less well functionally characterized. Although p150,95 has complement receptor activity for iC3b and has been designated complement receptor type 4, transfected cells expressing p150,95 do not bind iC3b-sensitized cells. We report that cells cotransfected with a human p150,95 alpha subunit and a chicken, but not human, beta subunit bind IgM-iC3b-coated erythrocytes, suggesting that interactions between the alpha and beta subunits can regulate p150,95 adhesiveness. Furthermore, purified human p150,95 binds to cell-bound iC3b-coated erythrocytes. Because binding to iC3b by cellular and purified p150,95 is specifically abolished by mAbs that localize to the I domain of p150,95, we suggest that the I domain of the p150,95 alpha subunit is an important ligand recognition site for iC3b.
authors.affiliation: Center for Blood Research, Harvard Medical School, Boston, MA 02115.
authors.forename: C A
authors.initials: CA
authors.lastname: Bilsland
authors.forename: M S
authors.initials: MS
authors.lastname: Diamond
authors.forename: T A
authors.initials: TA
authors.lastname: Springer
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D018845:CD11 Antigens; D018821:CD18 Antigens; D002460:Cell Line; D002645:Chickens; D002522:Chlorocebus aethiops; D003179:Complement C3b / Q000378:metabolism*; D000939:Epitopes; D004912:Erythrocytes / Q000276:immunology; D006801:Humans; D007962:Leukocytes / Q000276:immunology / Q000378:metabolism; D008024:Ligands; D017463:Receptors, Complement 3b / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D012397:Rosette Formation; D014162:Transfection
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D018845:CD11 Antigens; D018821:CD18 Antigens; D000939:Epitopes; D008024:Ligands; D017463:Receptors, Complement 3b; D011994:Recombinant Proteins; D003179:Complement C3b