Autoantibodies to purified nuclear proteins related to DNA metabolism during ageing and in SLE patients

In this study the specificity of circulating autoantibodies in ANA+ aged donors, ANA- donors and SLE patients was investigated by immunoblotting on total nuclear proteins and by ELISA on purified nuclear proteins, possibly related to DNA metabolism, such as DNA polymerase alpha, DNA-dependent ATPase, DNA Topoisomerase I, ssDBP, hnRNP, HMG and histones. Immunoblotting showed that sera from ANA+ aged donors present fewer antibodies to nuclear proteins, especially to those between 21,000 and 45,000, molecular weight (MW), than sera from SLE patients. When the specificity of antisera was further studied on purified nuclear proteins, it was found that the majority of sera from SLE patients react with most of the proteins tested, whereas sera from ANA+ aged donors mainly react with DNA polymerase alpha, DNA-dependent ATPase, DNA Topoisomerase I and histones. In addition, sera from a few ANA- donors also reacted with certain purified nuclear proteins in a statistically significant age-related manner.