Reactive oxygen species expose cryptic epitopes associated with autoimmunegoodpasture syndrome

Goodpasture syndrome is an autoimmune disease of the kidneys and lungs medi ated by antibodies and T-cells directed to cryptic epitopes hidden within b asement membrane hexamers rich in alpha 3 non-collagenous globular (NC1) do mains of type IV collagen. These epitopes are normally invisible to the imm une system, but this privilege can be obviated by chemical modification. En dogenous drivers of immune activation consequent to the loss of privilege h ave long been suspected. We have examined the ability of reactive oxygen sp ecies (ROS) to expose Goodpasture epitopes buried within NC1 hexamers obtai ned from renal glomeruli abundant in alpha 3(IV) NC1 domains. For some hexa meric epitopes, like the Goodpasture epitopes, exposure to ROS specifically enhanced recognition by Goodpasture antibodies in a sequential and time-de pendent fashion; control binding of epitopes to alpha 3(IV) alloantibodies from renal transplant recipients with Alport syndrome was decreased, wherea s epitope binding to heterologous antibodies recognizing all alpha 3 NC1 ep itopes remained the same. Inhibitors of hydrogen peroxide and hydroxyl radi cal scavengers were capable of attenuating the effects of ROS in cells and kidney by 30-50%, respectively, thereby keeping the Goodpasture epitopes la rgely concealed when compared with a 70% maximum inhibition by iron chelato rs. Hydrogen peroxide administration to rodents was sufficient to expose Go odpasture epitope in vivo and initiate autoantibody production. Our finding s collectively suggest that ROS can alter the hexameric structure of type I V collagen to expose or destroy selectively immunologic epitopes embedded i n basement membrane. The reasons for autoimmunity in Goodpasture syndrome m ay lie in an age-dependent deterioration in inhibitor function modulating o xidative damage to structural molecules. ROS therefore may play an importan t role in shaping post-translational epitope diversity or neoantigen format ion in organ tissues.