AUTOANTIBODIES RECOGNIZING PROTEINS COPURIFIED WITH PCNA IN PATIENTS WITH CONNECTIVE-TISSUE DISEASES

Objective. Proliferating cell nuclear antigen (PCNA), one of the targe t antigen recognized by lupus sera: has been reported to be present as a subnuclear multi-peptide complex. But autoantibodies reacting with components of PCNA complex are poorly understood. To study the specifi city of those autoantibodies, immunoreactivities of autoimmune sera ag ainst purified PCNA antigen were studied. Methods. PCNA antigens were purified from rabbit thymus extract by affinity column using murine mo noclonal antibodies (mAbs) to PCNA, TOB7, TO17 and TO30 Immunoreactivi ties of autoimmune sera against purified PCNA were analyzed by WE. Res ults. PCNA antigen purified by serum AK predominantly showed a 34 kD b and specific for PCNA in SDS-PAGE. When antigens were purified by anti -PCNA mAb TOB7 and TO30 which are known to be targeting different epit opes on PCNA antigen, SDS-PAGE analysis showed various mel. wt of prot eins in addition to the 34 kD PCNA while both AK and mAbs reacted only with 34 kD PCNA in WE. In WB using PCNA purified by TOB7, various imm unoreactivities were observed at 150, 66, 58, 48, 45, 37, 32 and 16 kD a in sera from patients with connective tissue diseases. Conclusions. These results suggested that many of the proteins copurified with PCNA were also targets of autoimmune responses and these autoantibody expr ession may be induced through antigen-driven mechanisms.