Disclosed is a method and a family of materials useful for removing immune complexes from blood preferentially to soluble antibodies. The material comprises analogs of proteins which bind to the Fc region of immunoglobulin. The analogs are produced by truncating or otherwise altering the amino acid sequence of the binding protein to reduce their affinity for Fc. An array of such analogs disposed about the surface of an insoluble matrix has the ability to form multiple points of attachment to the multiple Fc's in a complex so as to bind complex strongly, whereas only weak associations are developed between the Fc region of soluble IgG and individual analogs. The preferred analogs are truncated proteins homologous to a portion of the domains of Protein A or Protein G which bind with Fc. Complex may be removed from whole blood or serum using the material and conventional plasmapheresis techniques.