Moreover, antibodies to citrullinated EBV peptides have been described in RA [41–44], and Rossi et al. showed that ACPA from patients with RA have higher affinity for citrullinated autoantigens (in this case histone citrullinated peptide 1), than for citrullinated peptides derived from EBV proteins (i.e. exogenous antigens) [45], suggesting that these antibodies are initially produced against exogenous antigen and later selected and expanded by autoantigens. The gene discussed is PRTN3; the disease is rheumatoid arthritis.