Objective. To determine the frequency, clinical associations, and any major histocompatibility complex correlations of antifibrillarin antibodies in patients with systemic sclerosis (SSc).Methods. Antifibrillarin antibodies were determined by indirect immunofluorescence, immunoblotting, and immunoprecipitation, and HLA class I1 alleles by DNA oligotyping, in a large cohort of SSc patients.Results. Antifibrillarin was found in 8% of 335 SSc sera and was significantly more common in blacks (16%) than whites (S%), in males (33%) than females (14%), and in patients with cardiac, renal, or gut involvement. The HLA class I1 haplotype DRBZ *Z302, DQBZ*0604 was found significantly more frequently in SSc patients with antifibrillarin compared with racematched normal controls and 260 SSc patients without antifibrillarin. In addition, 1 or more of the HLA-DQB1

A B S T R A C T When tissue sections are extracted with 0.1 N HCl, cellular nuclear proteins, including histones, are removed but nuclear DNA is retained. Histones can be reconstituted back to nuclear DNA in acid-extracted tissue sections so that the resulting nuclear substrate -is composed only of DNA and histones and does not contain acidic nuclear protein antigens. The resulting DNA-histone tissue substrate can be used in the immunofluorescent method for specific detention of antibodies to histones. Sera from 23 patients with drug-induced lupus erythematosus (procainamide 19, isoniazid 2, nitrofurantoin 2) and 20 patients with idiopathic (not drug-induced) systemic lupus erythematosus (SLE) were studied. All 23 patients with drug-induced lupus erythematosus (LE) lost nuclear staining on acid-extracted sections. In contrast, only 12 of 20 with idiopathic SLE lost nuclear staining on acid-extracted tissues, and in the remaining 8, there was no significant fall in titer. In the drug-induced LE group, loss of nuclear staining was due to the absence of histones on the substrate because with histone-reconstituted sections, 22 of 23 again became positive for nuclear staining at titers equal to or at one doubling dilution below titers on unextracted tissues. In contrast, of the 12 idiopathic SLE sera which lost nuclear staining, only 5 regained nuclear staining on histone-reconstituted tissue sections. In idiopathic SLE, antinuclear antibodies are heterogeneous in specificities and may consist of antibodies to native DNA, histones, or nonhistone proteins. In contrast, antinuclear antibodies in druginduced LE are less heterogeneous and mainly consist of antibodies to histones.

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There is a rapid proliferation of new technologies to identify an ever increasing spectrum of autoantibodies in diverse medical conditions that range from organ-specific autoimmune diseases to systemic rheumatic diseases. Although many laboratories have adopted diagnostic platforms, such as enzyme linked immunoassays (ELISAs), to improve turn around times and meet budget constraints, the prevailing evidence is that the rapid adoption of new technologies is not attended by an appropriate balance of assay sensitivity and specificity. Emerging diagnostic technologies include addressable laser bead immunoassays, microarrays in microfluidics platforms and nanobarcode particles. Although these technologies provide advantages of high-throughput, multiplexed autoantibody assays that can be coupled to other disease specific biomarkers (ie, cytokines, single nucleotide polymorphisms) there is a clear need for standardization and internal validation before they are adopted into the clinical diagnostic laboratory.

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