Canine antinuclear antibodies: Comparison of immunofluorescence staining patterns and precipitin reactivity

The occurrence of antinuclear antibodies (ANAs) against several specific nu clear antigens is clearly associated with certain systemic rheumatic disord ers in human patients. Determination of ANAs on a routine basis, usually by indirect immunofluorescence (IIF) technique, has therefore become an impor tant diagnostic tool. The subdividing of positive ANA-sera into different n uclear IIF staining patterns often gives clues to antibody specificity. The present investigation aimed at studying whether such subgroups of staining patterns in IIF ANA positive canine sera may represent certain specific AN As that can be verified by standard methods used for specificity determinat ion in humans. The presence of precipitating antibodies, determined by the Ouchterlony imm unodiffusion (ID) technique, was found to be strictly associated with a pos itive IIF ANA, exhibiting a speckled staining pattern without any chromosom al reactivity. None of the sera with chromosomal reactivity contained preci pitating antibodies. Among the ID positive serum samples, different antigen ic reactivities were detected, represented by different ID subgroups. Only 1 of the 4 main subgroups obtained by ID showed identity with any of the co mmon and disease-associated human ANA specificities, exhibiting anti-RNP re activity. One of these serum samples concomitantly exhibited precipitating antibodies against the Sm antigen.