Immunological testing for specific antibodies to streptococcal metabolic products yields important information about previous streptococcus infections. Antibodies are produced against the pathogen and its metabolic products. One example is the antibody to streptolysin O, an enzyme produced by Lancefield group A β‑hemolytic streptococci. Determination of antistreptolysin O is performed when toxic and sensitizing associated illnesses occur, such as rheumatic fever (major symptoms: carditis, polyarthritis, chorea minor, subcutaneous nodules, erythema annulare) and poststreptococcal acute glomerulonephritis.