THE STABILITY OF NEOEPITOPES RECOGNIZED BY REGULATORY RHEUMATOID FACTOR AFTER REMOVING THE MODIFYING AGENT REQUIRED FOR THEIR FORMATION
Fc fragments of IgG exposing neoepitopes recognized by the regulatory rheumatoid factor have the ability to suppress autoimmune reactions and reduce symptoms of rat collagen-induced arthritis. To induce neoepitopes in Fc fragments of IgG a modifying agent is used. This modifying agent can cause undesirable reactions when introduced into the body. Therefore it is necessary to remove it after Fc fragments modifying. The aim of the study was to fi nd out whether neoepitopes recognized by the regulatory rheumatoid factor remain on Fc fragments of IgG after removal of the modifying agent. It has been found that Fc IgG fragments can be purifi ed from a modifying agent by size exclusion chromatography on a Superdex 200. Removal of the modifying agent leads to the loss of neoepitopes recognized by the regulatory rheumatoid factor on Fc IgG fragments. The loss of neoepitopes after the removal of the modifying agent is accompanied by the oxidation of the sulfhydryl groups of the hinge region which were present on Fc fragments carrying the neoepitopes. This fact suggests that in order to preserve on the Fc fragments of IgG neoepitope recognized by the regulatory rheumatoid factor the reduced state of cysteine residues of the hinge region must be maintained and the modifying agent used creates the necessary conditions for this.