SS-A/Ro52, an autoantigen involved in CD28-mediated IL-2 production. 
An autoantibody against SS-A/Ro52 (Ro52) is most frequently found in the sera of patients with Sjögren's syndrome, systemic lupus erythematosus, and congenital heart block from anti-Ro52 Ab-positive mother.  However, the physiological function of the autoantigen SS-A/Ro52 has not yet been elucidated.  In this study, we describe the role of Ro52 protein in T cell activation.  Overexpression of SS-A/Ro52 in Jurkat T cell resulted in enhanced IL-2 production following CD28 stimulation.  Furthermore, transfection of anti-Ro52-specific small RNA duplexes partially blocked the expression of native and overexpressed Ro52 in Jurkat T cell, resulting in decreased IL-2 production via CD28 pathway in these cells.  Finally, intracellular localization of Ro52 dramatically changed following CD28 stimulation.  Our data reveal a novel function of Ro52 in CD28-mediated pathway, which eventually contributes to cytokine production and expression of the T cell biological programs.