To assess the specificity of the effect of TNF blockade on insulin resistance, we prospectively studied seven RA patients (median age 63 years, median disease duration 13 years) with high disease activity (median DAS28 5.92) treated with abatacept (CTLA4.Ig), a biologic agent that targets T-cell co-stimulation. This evidence concerns the gene CTLA4 and rheumatoid arthritis.