Quantitative studies of immunofluorescent staining. 3. Comparison of different antigens in an indirect immunofluorescent staining system for human IgG using the basement zone antibodies of bullous pemphigoid.

Antibodies against basement zone in the sera of two patients with bullous pemphigoid were studied by indirect immunofluorescence. Monkey and guinea-pig lip and oesophagus were used as antigen and the effects were observed of using various concentrations of the human serum and the fluorescein-labelled goat anti-human IgG conjugate. The plateau titre of the human serum depends upon the fluorescein/protein ratio of the conjugate. The highest dilution of conjugate giving this plateau titre is called the plateau endpoint and depends upon the amount of antibody in the conjugate, i.e. the unitage of the conjugate. A serum with a high titre of antibody gave similar results with monkey and guinea-pig tissues but a serum with a low titre gave variations in the plateau titre and plateau endpoint even when tissue from only one species was used. It was concluded that quantitative differences exist in the antigenic strength of basement membranes of different tissues even within one species. Guinea-pig lip appears to be suitable for diagnosis of bullous pemphigoid.