Autoantibodies to 60kDa SS-A/Ro yield a specific nuclear myriad discrete fine speckled immunofluorescence pattern

Objectives: To report on a novel immunofluorescence pattern specifically associated with antibodies to SS-A/Ro.

Methods: A novel immunofluorescence pattern, herein designated SS-A/Ro pattern, was characterized as myriad discrete fine speckles throughout the nucleus. Eighty-six sequential samples presenting the SS-A/Ro pattern and 64 samples presenting non-SS-A/Ro nuclear fine speckled pattern at the ANA-HEp-2 routine were screened for SS-A/Ro reactivity. Conversely, 48 samples with known reactivity to 60kDa SS-A/Ro, 13 samples with exclusive reactivity to 52kDa SS-A/Ro, and 48 SS-A/Ro-negative samples were analyzed for the ANA-HEp-2 pattern.

Results: Eighty-five of the 86 samples (98.8%) presenting the SS-A/Ro pattern and 15 of the 64 (23.4%) samples with non-SS-A/Ro fine speckled pattern reacted with 60kDa SS-A/Ro. Conversely, 44 (91.6%) of 48 samples with known reactivity to 60kDa SS-A/Ro presented the SS-A/Ro pattern and four (8.4%) presented non-SS-A/Ro fine speckled pattern. None of the 48 anti-SS-A/Ro-negative samples and none of anti-52kDa SS-A/Ro-positive samples yielded the SS-A/Ro pattern. This immunofluorescence pattern was observed in different commercial HEp-2 cell slides and in homemade HEp-2 cell slides.

Conclusions: The SS-A/Ro pattern belongs to the group of immunofluorescence patterns that hold strong association with the respective autoantibody specificities, such as those associated with CENP-F and NuMA-1. The identification of the SS-A/Ro pattern at the ANA-HEp-2 screening routine shall lead to specific tests for the identification of anti-SS-A/Ro antibodies.