[Detection of antinuclear antibodies and their significance as disease markers]

The improvement of the quality control in the detection of fluorescent antinuclear antibodies (FANA) have decreased the differences among institutions. However, the positive lower or upper reference limit and the criteria for the determination vary among laboratories. By examining 725 sera from children and 227 sera from healthy adults, we proposed the titers of 160-320 for children and 80-160 for adults as the positive lower limits. The higher positive incidence in the children's sera might be due to some abnormality in the ANA production or the higher sensitivity of the reagents used. The clinical significances of the anti-U1RNP antibody and anticentromere antibody (ACA) in ANA have been described. The anti-U1RNP antibody, present in only MCTD and related disorders, might play some role in the development of Raynaud's phenomenon and symptoms in a case of neonatal lupus erythematosus. ACA was detected in sera not only of CREST syndrome patients but also of PBC patients. The functions and molecular structures of nuclear antigens have recently been extensively investigated. However, the pathogenetic significance of most of the ANA and the mechanism of their production have not been clarified yet.