Antinuclear factors in sera from healthy blood donors

Sera obtained from 466 healthy blood donors were investigated for presence of granulocyte-specific and organ-nonspecific antinuclear factors of the IgM, IgA and IgG classes, 110 sera also for complement-fixing and IgD class antinuclear factors. When undiluted sera were studied, most sera were found to contain antinuclear factors of one or more immunoglobulin classes (77 per cent). IgM, IgA and IgG antinuclear factors were found in 53, 44 and 14 per cent, respectively. At dilution 1:16, antinuclear factors of the IgM class were still detected in 16 per cent of the sera, while IgA and IgC antinuclear factors wre demonstrated in 6 and 2 per cent, respectively. Organ-nonspecific antinuclear factors were clearly more common than granulocyte-specific antinuclear factors. No serum contained complement-fixing or IgD class antinuclear factors. This study indicates the importance of using qualitative as well as quantitative techniques to distinguish between antinuclear factors in health and disease.