THE RELATIONSHIP OF ASE-1 AND NOR-90 IN AUTOIMMUNE SERA

Objective, The nucleolar proteins ASE-1 and NOR-90 can become confused because they have similar cytological and Western blot features. We i nvestigated the frequency and relationship between these 2 proteins an d identified clinical features of patients with ASE-1 antibodies. Meth ods. The characteristics of ASE-1 and NOR-90 are shown by indirect imm unofluorescence (IIF) and Western blot data. The sera are characterize d by their ability to immunoprecipitate the in vitro transcription and translation (TnT) product of either the ASE-1 or NOR-90 cDNA. Clinica l features were obtained by retrospective chart review. Results. Of th e 15 sera identified as potentially NOR-90 positive by IIF and Western blot 8/15 (53%) were able to immunoprecipitate a NOR-90 TnT product. Of the remaining 7 sera, 4 (57%) were only able to immunoprecipitate a n ASE-1 TnT product. Four (57%) of the remaining 7 sera were able to i mmunoprecipitate an ASE-1 TnT product. In a second cohort of confirmed NOR-90 positive sera, 2/8 (25%) were able to immunoprecipitate an ASE -1 TnT product. In total, ASE-1 autoantibodies were found in 6/16 (37. 5%) of confirmed NOR-90 sera from both cohorts. There were no common c linical features found in seven ASE-1 positive patients; however, 3 (4 3%) had a malignancy and 3 (43%) had slowly progressive systemic scler osis. Conclusion. Autoantibodies to ASE-1 and NOR-90 can occur alone o r together in autoimmune sera. Due to their similar IIF and Western bl ot profile the only way to correctly characterize these sera is by imm unoprecipitation of the appropriate TnT product.