In this study, we investigated the changes in blood-circulating miRNAs in RA patients before and after treatment with abatacept, a biologic agent used for RA that consists of an extracellular domain of human cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) and the Fc portion of human immunoglobulin G1. The gene discussed is CTLA4; the disease is rheumatoid arthritis.