Anti-proteasome activator 28α is a novel anti-cytoplasmic antibody in patients with systemic lupus erythematosus and Sjögren’s syndrome
Masakazu Matsushita1 , Ran Matsudaira1 , Keigo Ikeda1 , Masuyuki Nawata1 , Naoto Tamura1 , Yoshinari Takasaki1
17 June 2009
14 July 2009
14 August 2009
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We evaluated the extent to which anti-proteasome activator (PA) 28α antibodies act as anti-cytoplasmic antibodies in systemic lupus erythematosus (SLE) and Sjögren’s syndrome (SS). Sera from 46 SLE patients without SS, 11 SLE patients with SS, and 45 primary SS patients were tested. Using anti-PA28α and anti-PA28γ (Ki) antibodies purified from nitrocellulose membranes onto which recombinant PA28α and Ki had been transferred, the cellular distributions of the targeted antigens were analyzed immunohistochemically. In addition, the incidence of anti-PA28α antibodies was compared with those of other anti-cytoplasmic antibodies. Immunofluorescent staining showed that purified anti-PA28α antibodies reacted with the cytoplasm of HEp-2 cells, whereas purified anti-Ki antibodies reacted with nucleoplasm. Among the 15 SLE patients without SS, the six SLE patients with SS, and the 30 primary SS patients who were anti-cytoplasmic-antibody positive, anti-SS-A/Ro antibodies were the most frequently detected (53, 67, and 70%, respectively); anti-PA28α antibodies were, respectively, detected in 33, 50, and 40% of those patient groups, incidences that were higher than those of anti-ribosomal P, anti-smooth muscle and anti-mitochondrial M2 antibodies. These results show that anti-PA28α antibodies are major anti-cytoplasmic antibodies in patients with SLE and SS, and the distinct cellular distributions of PA28α and Ki suggest these proteins are associated with different cellular functions.
Anti-PA28α antibody - Anti-Ki antibody - Anti-cytoplasmic antibody - Systemic lupus erythematosus - Sjögren’s syndrome