Autoantibodies in SLE but not in scleroderma react with protein-stripped nucleosomes

Autoantibodies against nucleosomes (ANuA) are known to be sensitive markers for systemic lupus erythematosus (SLE),but their clinical relevance seemed to be limited because sera from patients with progressive systemic sclerosis (PSS) also showed positive reactions with conventional ANuA ELISA test systems (anti-Nu1 ELISA). It was generally assumed that ANuA were associated with both diseases.Using discontinuous sucrose gradient centrifugation to generate pure nucleosomes,we discovered by chance that at the 30–50% sucrose interface an antigen (Nu2) banded which was demonstrably free of non-histone components and histone H1.