title: Autoimmune response to proteins of proliferating cell nuclear antigen multiprotein complexes in patients with connective tissue diseases.
abstract: OBJECTIVE
  To analyze the autoimmune response to the proliferating cell nuclear antigen (PCNA) multiprotein complex in patients with connective tissue diseases (CTD).
  
  
  METHODS
  The PCNA complex was purified by affinity chromatography using anti-PCNA monoclonal antibodies. Then 196 serum samples from patients with systemic lupus erythematosus (SLE) and 82 from patients with other CTD were tested for reactivity with the complex by immunoblotting.
  
  
  RESULTS
  Of 196 SLE sera, 61 (31%) reacted with at least one component of the PCNA complex, and most reactive sera contained autoantibodies to several components of the complex. Autoantibodies to PCNA complex were less common in patients with other CTD, and most of their sera reacted only with one or a few proteins in the complex. Two out of 20 scleroderma sera reactive with 100, 85, and 70 kDa proteins in the PCNA complex also had autoantibodies to topoisomerase I (topo I) antibodies, which is an element of the complex. These findings suggest that the autoimmune response to the PCNA complex was specific for SLE. Anti-PCNA complex antibodies were associated with an increased serum level of PCNA detected by ELISA. The spreading of the autoimmune response to the elements of the complex was observed in parallel with the increased serum PCNA level when a series of sera from a lupus patient were tested longitudinally. In addition, anti-PCNA complex antibodies were significantly correlated with lupus erythematosus cells.
  
  
  CONCLUSIONS
  The "antigen-drive" system may play a crucial role in inducing the autoimmune response to the PCNA complex in patients with SLE.
authors.affiliation: Department of Internal Medicine and Rheumatology, Juntendo University School of Medicine, Tokyo, Japan.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Kaneda
authors.forename: Yoshinari
authors.initials: Y
authors.lastname: Takasaki
authors.forename: Ken
authors.initials: K
authors.lastname: Takeuchi
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Yamada
authors.forename: Masuyuki
authors.initials: M
authors.lastname: Nawata
authors.forename: Masakazu
authors.initials: M
authors.lastname: Matsushita
authors.forename: Ran
authors.initials: R
authors.lastname: Matsudaira
authors.forename: Keigo
authors.initials: K
authors.lastname: Ikeda
authors.forename: Kenjiro
authors.initials: K
authors.lastname: Yamanaka
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hashimoto
mesh_terms: D015551:Autoimmunity; D002846:Chromatography, Affinity; D003240:Connective Tissue Diseases / Q000276:immunology* / Q000503:physiopathology; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000276:immunology; D046912:Multiprotein Complexes / Q000276:immunology*; D018809:Proliferating Cell Nuclear Antigen / Q000737:chemistry / Q000276:immunology*
chemical_list: D046912:Multiprotein Complexes; D018809:Proliferating Cell Nuclear Antigen