Bozec et al. demonstrated that RA patients treated with abatacept (CTLA-4-Fc), which is approved for clinical use in RA, remarkably reduced osteoclast precursors and downregulated osteoclast-differentiation markers such as c-Fos, NFATc1, c-Fms, and RANK [12]. The gene discussed is FOS; the disease is rheumatoid arthritis.