CLINICAL RELEVANCE AND HLA ASSOCIATION OF AUTOANTIBODIES AGAINST THE NUCLEOLUS ORGANIZER REGION (NOR-90)

Objective. NOR-90 autoantibodies directed against the nucleolus organi zer region (NOR) have been described as rare scleroderma associated an tibodies. We studied the clinical features of patients with NOR-90 ant ibodies as well as their HLA phenotype. Methods. NOR-90 antibodies wer e detected by indirect immunofluorescence assay using HEp-2 cells, by chromosome spreads as a substrate and in addition by Western blot anal ysis with HeLa-S3 nucleolar extract. HLA antigens of the NOR-90 antibo dy positive patients were typed with the standard NIH complement depen dent microcytotoxicity test. Results. Nine sera selected by means of t he indirect immunofluorescence revealed a typical double band pattern of about 90 kDa identical with the pattern of 2 NOR-90 reference sera by Western blot analysis. Only one patient positive for NOR-90 antibod ies suffered from systemic sclerosis (limited cutaneous scleroderma). The other patients with NOR-90 antibodies showed no signs of systemic sclerosis. All patients with NOR-90 antibodies were women and 8 of 9 p atients (89 versus 13% of healthy controls, p(corr) <0.001) were posit ive for the HLA-DR1 allele. Conclusion. In contrast to the first repor t on NOR-90 antibodies we demonstrated no association of these antibod ies with systemic sclerosis; however, we found strong evidence for an immunogenetic background of NOR-90 antibody formation.