To determine if hepcidin could be expressed independent of TLR4 activation, we measured serum hepcidin levels in C3H/HeJ mice (TLR2+/+, TLR4-/-) and compared the values to C3H/HeSnJ mice (TLR2+/+, TLR4+/+) after infection with M. arthritidis. This evidence concerns the gene TLR4 and infection.