Serum hepcidin is elevated in mice infected with B burgdorferi. (A) C3H and C57BL/6 mice were infected with B burgdorferi. Arthritis severity was determined by measuring rear ankle joint diameter in infected and control mice 4 weeks after infection. (B) C3H and C57BL/6 mice were infected with B burgdorferi as in panel A. Four weeks after infection, serum hepcidin levels were measured and compared with uninfected controls. (C) C3H mice were infected with B burgdorferi as in panel A. Serum hepcidin levels were measured at weekly intervals using a bioactive assay (top panel) and dot blot (bottom panel) for a total of 4 weeks and compared with control mice. (D) C3H mice were infected with B burgdorferi and sacrificed after 4 weeks of infection. RNA was isolated and purified from the livers and spleens. Hepcidin and actin transcripts were analyzed by RT-PCR.