Alpha‐fodrin as a putative autoantigen in Graves’ ophthalmopathy

Summary Alpha‐fodrin, an intracellular organ‐specific cytoskeleton protein is a recently identified autoantigen associated with Sicca‐ and Sjögren's syndrome (SS). SS frequently affects patients with Graves’ ophthalmopathy (GO). We have therefore cloned and expressed the human recombinant 120‐kDa fodrin‐fragment. A sequential purification procedure was applied to isolate the recombinant protein. Using sera from patients with SS, the antigenicity of the purified fodrin fragment was demonstrated by immunoblotting. Sera from 144 patients with GO and 1200 blood donors were screened for the presence of anti‐α‐fodrin IgA and IgG antibodies by a newly developed ELISA using the human α‐fodrin fragment as an autoantigen. In contrast to controls (<1% IgA only, P  < 0·001) and to subjects with various autoimmune diseases ( P  < 0·001), α‐fodrin antibodies were detected in 22% of patients with GO ( n  = 32). IgA and IgG antibodies were present in 21 (15%) and 14 (10%) GO subjects, respectively. A total of 45 patients with GO (31%) had at least one fodrin‐ or SS‐antibody. GO patients with SS showed SS‐ and high titres of α‐fodrin‐antibodies. In GO patients, fodrin antibodies correlated with TPO‐ ( P  < 0·05) and SS‐A ( P  = 0·002) antibodies. Thus, for the first time, antibodies reactive with fodrin are reported in patients with GO.