The importance of tissue substrate in the SS-A/Ro antigen-antibody system

Using highly monospecific anti-SS-A containing sera and specific antibody to SS-A antigen dissociated from immune precipitates, tissue sections and cell culture lines were evaluated by the indirect immunofluorescence technique to determine the intracellular location, tissue distribution, and species specificity of the SS-A/Ro antigen. The SS-A/Ro antigen is predominantly a nuclear antigen giving an immunofluorescence staining pattern of discrete nuclear speckles. The SS-A/Ro antigen is present in a wide variety of human tissue, including kidney and liver parenchymal cells, lymphocytes, fibroblasts, and epithelioid cells. However, the SS-A/Ro antigen does appear to have a variable species distribution, with significant quantities of the antigen detected by immunofluorescence in cells of human, monkey, dog, and guinea pig, but absent to low amounts detected in cells of mouse, rat, rabbit, hamster, and chicken.