IRF5 and rheumatoid arthritis: Ab reactivity reached the highest levels for IRF5, EBV and IL-2 (56%, 44% and 39%, respectively) in RA with significantly lower values among HCs (7–9%, p < 0.0001), which suggests a possible cross-reaction between IRF5/EBV homologous antigens and shifts in T cell balance disrupted by anti-IL-2 Abs.