Abzymes (catalytic autoantibodies) belong to an absolutely new group of physiologically active substances with dual characteristics: they represent a pool of canonical autoantibodies and possess catalytic activity. Among them, proteolytic and DNA-hydrolyzing autoantibodies are of special value. Abzymes are an important pathogenic factor in the progression of clinical autoimmunity syndrome. The presence of autoantibodies against various autoantigens is accompanied by their high catalytic potential. The increase in this activity correlates with serum levels of the autoantibodies, clinical manifestations of autoimmune disorders, disease severity and the rate of progressing disability. Abzymes are crucial for immune homeostasis regulation. They can be of practical value in the development of modern immunodiagnostic tools and schedules of immunotherapy.