An improved solid-support, affinity immunoadsorbent suitable for extracorporeal perfusion of plasma is reported. This consists of hydroxyapatite microspheres coated with a thin layer of poly(vinyl alcohol) and immobilized phenylalanine as ligand. This adsorbent can remove IgG immunoglobulins specifically from plasma. The modified adsorbent may be used for direct hemoperfusion as a cheaper alternative to plasma adsorption therapy by eliminating cell separator for selective removal of antibodies belonging to immunoglobulin G class.