title: Assay of membrane complement receptors (CR1 and CR2) with C3b- and C3d-coated fluorescent microspheres.
abstract: A sensitive and specific fluorescence assay for membrane complement (C) receptors (CR1 and CR2) was developed with purified C3b and C3d fragments coupled to fluorescent microspheres (0.9 mu diameter). C3-microspheres (C3-ms) bound to cells with low numbers of receptors that were undetectable by other assay techniques. Inhibition studies with anti-CR1 and anti-CR2 demonstrated that C3b-ms and C3d-ms bound exclusively to CR1 and CR2, respectively. Preparation of the C3-ms required only small amounts of partially purified C3 and no immunoglobulin or other C components. Once formed, the C3-ms were stable for up to 4 mo at 4 degrees C.
mesh_terms: D001667:Binding, Competitive; D002462:Cell Membrane / Q000276:immunology; D003176:Complement C3 / Q000378:metabolism*; D003179:Complement C3b / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006801:Humans; D008863:Microspheres; D011309:Preservation, Biological; D011951:Receptors, Complement; D012397:Rosette Formation
chemical_list: D003176:Complement C3; D011951:Receptors, Complement; D003179:Complement C3b