Intraperitoneal administration of LPS in transgenic mice carrying a human SE-coding HLA-DRB1 allele caused increased serum levels of TNF-α and ACPA production, as well as terminal phalanx bone destruction (22), thereby suggesting a mechanistic basis for the long documented association between RA and protein citrullination. The gene discussed is HLA-DRB1; the disease is rheumatoid arthritis.