RNPC3 and systemic lupus erythematosus: However, hallmark SLE autoantibodies primarily target nuclear antigens such as double-stranded DNA (dsDNA), Sjögren’s syndrome A (SSA), Sjögren’s Syndrome B (SSB), ribonucleoprotein (RNP) and Smith (Sm), which are ubiquitously expressed across all organs and cells rather than being specific to the heart7.