Assay of membrane complement receptors (CR1 and CR2) with C3b- and C3d-coated fluorescent microspheres

J Immunol. 1982 Jan;128(1):186-9.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Binding, Competitive
  • Cell Membrane / immunology
  • Complement C3 / metabolism*
  • Complement C3b / metabolism*
  • Fluorescent Antibody Technique*
  • Humans
  • Microspheres
  • Preservation, Biological
  • Receptors, Complement*
  • Rosette Formation


  • Complement C3
  • Receptors, Complement
  • Complement C3b