Immune response to extracellular and somatic antigens in streptococcal infection and sequelae

The aim of the present study is to define the temporal relationships of the IgM and IgG responses to Streptococcal group A carbohydrate (CHO) in rabbits and in man. Rabbits were immunized with group A streptococci and the development of anti-group A carbohydrate (ACHO) was studied. ACHO which appeared one week after the beginning of immunization belonged to the 19S class of immunoglobulins (IgM). A two- to four-fold rise in ACHO titers and immunoglobulins of the 7S class (IgG) were observed after two weeks. Three weeks after the beginning of immunization, the ACHO titer was at a maximum. In the following months no further rises in titer were seen, and the antibodies belonged mostly to the IgG class. IgM and IgG responses to streptococcal CHO and to extracellular antigens in patients with pharyngitis, acute rheumatic fever (ARF), and acute glomerulonephritis (AGN) were studied. Higher values of IgM were found in pharyngitis and AGN sera than in ARF sera, probably reflecting the interval between streprococcal infection and time of bleeding. ACHO antibodies persisted in patients' sera for long periods and belonged to IgG and IgM. This suggests a continuous, rather than a persistent, production of ACHO.