A clinical study of immunoglobulin class specific antibody response following hepatitis A

Anti-HAV activity was determined by radioimmunoassay for serum fractions of IgG, IgM, and IgA separated with sucrose gradient centrifugation and immunoglobulin absorption using class-specific anti-immunoglobulin. Anti-HAV following hepatitis A was detected initially in IgM and IgA within one week after onset, and also detected in IgG within the next one week. IgM anti-HAV activity reached its peak level at the 21st-30th day of illness with a mean titer of 16.4 by RIA, and then declined gradually, whereas serum IgM concentration increased and reached the peak earlier, and no correlation was seen between them. IgG anti-HAV activity increased rapidly and it exceeded a RIA titer of 80 in 80 days from onset in 12 of the 18 cases. According to the kinetics of IgM and IgG anti-HAV, four types of antibody response following the disease were observed. However, no correlation between antibody response patterns and clinical findings was seen, therefore less relationship of anti-HAV to the liver cell injury was indicated. Furthermore, it was suggested that some immunological mechanisms controlled the level of antigen-specific antibody activity, which maintained the high level of IgM antibody in case of poor response of IgG antibody.