Sera from patients suffering from systemic
autoimmune diseases such as
systemic lupus erythematosus (SLE) and
systemic sclerosis (SSc) have been shown to contain reactivities to nuclear components.
Autoantibodies specifically targeting nucleolar
antigens are found most frequently in patients suffering from SSc or SSc overlap syndromes. We determined the prevalence and clinical significance of
autoantibodies directed to nucleolar
RNA-
protein complexes, the so-called
small nucleolar ribonucleoprotein complexes (snoRNPs). A total of 172 patient sera with antinucleolar
antibodies were analysed by immunoprecipitation. From 100 of these patients clinical information was obtained by chart review.
Autoantibodies directed to snoRNPs were detected not only in patients suffering from SSc and primary Raynaud's phenomenon (RP), but also in patients suffering from SLE,
rheumatoid arthritis (RA) and
myositis (PM/DM).
Antibodies against box C/D small snoRNPs can be subdivided in antifibrillarin positive and antifibrillarin negative reactivity. Antifibrillarin-positive patient sera were associated with a poor prognosis in comparison with antifibrillarin negative (reactivity with U3 or U8
snoRNP only) patient sera. Anti-Th/To
autoantibodies were associated with SSc, primary RP and SLE and were found predominantly in patients suffering from decreased co-diffusion and oesophagus motility and
xerophthalmia. For the first time
autoantibodies that recognize box H/ACA snoRNPs are described, identifying this class of snoRNPs as a novel autoantigenic activity. Taken together, our data show that antinucleolar patient sera directed to
small nucleolar ribonucleoprotein complexes are found frequently in other diseases than SSc and that categorization of diagnoses and clinical manifestations based on
autoantibody profiles seems particularly informative in patient sera recognizing box C/D snoRNPs.