Abstract: Receptors, characterized by the fact that they consist of the product obtained by affinity chromatography on a column coupled with 3 G8 antibodies or lectins or polyclonal anti-receptor FcR antibodies of a biological fluid of human origin, then by gel permeation. The spectrum of said product, electrophoresis acrylamide gel in reducing condition, comprising a major band corresponding to a molecular mass of between 72000 and 76000 daltons, and a number of minor bands. According to its purified form, the receptor consists of a glycoprotein with a molecular mass of between 72000 and 76000 daltons, recognized by ELISA and Western Blotting by the monoclonal anti-Leu 11b antibody. Application of said receptors to diagnosis and to follow-up treatment of diseases involving Fc receptors (infectious diseases, diseases of the autoimmune system, rejection of transplants, cancer and myeloma and AIDS), as well as to the study of human polymorphisms.