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.

Immunogenicity and Specificity of Collagen

Rabbit antisera to acid-soluble calf collagen were used for cross-reaction studies with sheep, rat, guinea pig, rabbit and carp collagen in hemagglutination-inhibition tests. Advantage was taken of the use of three antibody fractions differing in specificity. One of them possessed a general collagen specificity, the others were species-specific and directed either to pepsin-stable or pepsin-labile determinants. Some of the antisera contained only one of the antibody fractions, in other cases they were separated on an immunoadsorbent.

The antibodies with general collagen specificity reacted with all the collagens, indicating a common antigenic determinant. Small but still significant differences observed in inhibition tests suggest, however, that these determinants are not identical but only similar in structure. The species-specific antibody fraction to pepsin-stable determinants cross-reacted with sheep and rat collagen or with sheep collagen only. The third antibody fraction, which in contrast to the others is directed to pepsin-labile structures of collagen, cross-reacted either with sheep collagen or showed no cross-reaction at all. The results were interpreted for the existence of at least five distinct antigenic determinants on calf collagen.