Prevalence and characteristics of anti-56K/annexin XI autoantibodies in systemic autoimmune diseases.

Objective: To investigate the occurrence and features of anti-56K/annexin XI autoantibodies in sera from patients with various systemic autoimmune diseases, including rheumatoid arthritis, systemic lupus erythematosus, Sjögren's syndrome, systemic sclerosis, polymyositis and Raynaud's phenomenon.
Methods: Anti-56K/annexin XI autoantibodies were detected by an enzyme linked immunosorbent assay using the bacterially expressed recombinant protein as antigen.
Results: Anti-56K/annexin XI autoantibodies were found in a substantial number of patient sera (4.1-10.1%), but are rarely detected in sera from healthy controls and from patients with infectious diseases. Disease specificity was not observed. The majority of these autoantibodies belong to the IgG class and their titers in positive sera are at least as high as those of other well defined autoantibodies.
Conclusion: Anti-56K/annexin XI autoantibodies frequently occur in systemic autoimmune diseases in contrast to infectious diseases and healthy individuals and are primarily of the IgG isotype, consistent with an antigen driven mechanism of autoantibody production.