A new immunoenzyme tracer for localization of antibodies in immunohistology: peroxidase-labeled protein A.

Protein A from Staphylococcus aureus, characterized by high affinity binding properties for IgG-type antibodies, was labeled with peroxidase to form a stable immuno-histological tracer molecule of comparatively low molecular weight. It has been used for demonstration of antibodies against tissue antigens, in direct and indirect techniques, and the findings were consistent with those in routine immunofluorescence and in staining with peroxidase-coupled anti-IgG. In comparison, the lowest unspecific tissue adsorption and staining was obtained with Protein A-peroxidase in buffer containing glucose and mannose. The immunohistological preparations were mounted and stored for documentation without apparent loss of staining.