The bound IgG antibodies react specifically with anti-human-IgG conjugated to horseradish peroxidase (HRP). Within the incubation period of 30 min at RT, excessive conjugate is separated from the solid-phase immune complexes by the following wash step. HRP converts the colorless substrate solution of 3,3',5,5'-tetramethyl benzidine (TMB) added into a blue product. The enzyme reaction is stopped by dispensing an acidic solution into the wells after 15 min at room temperature turning the solution from blue to yellow. Sample Types: serum, plasma. Range: n/a. Sensitivity: Cut Off Control. Time: 2 hours ? Systemic autoimmune diseases such as systemic lupus erythematosus, scleroderma, rheumatoid arthritis, Sjoegren's syndrome, dermatomyositis, mixed connective tissue disease are characterized by the appearance of a variety of autoantibodies directed against components of the cell nucleus.