Abstract
Chickens hyperimmunized with group A streptococcal vaccine often synthesize high levels of antibody to group A streptococcal carbohydrate (SACHO). Indirect immunofluorescent analysis revealed that sera of these chickens also contain antinuclear antibodies capable of reacting with chicken erythrocyte nuclei (EANA) at titers up to 2,560. Removal of the anti-SACHO antibodies from hyperimmune serum did not significantly reduce EANA titers, indicating that anti-SACHO antibodies are not responsible for the EANA reactions. The time course for antibody development as well as the immunoglobulin class distribution of EANA and anti-SACHO antibodies were very similar. Localization of EANA activity to Fab fragments indicated that the immunfluorescent reaction represents an antigen-antibody reaction. Findings point out an important consequence of using chicken immunoglobulin Y in immunofluorescent assays. The purified Fc fragment of immunoglobulin Y is cytophilic for the substrate when tested at high concentrations, which suggests that some cytophilic immunoglobulins are involved in the reaction.