MD-1–deficient mice were impaired in LPS-induced antibody production.

Littermate control (○) and MD-1–deficient mice (●) were immunized intraperitoneally with TNP-LPS (20 μg per mouse) and bled 1 and 2 weeks later. Five mice were used for each group. Titers of TNP-specific IgM or IgG3 were measured with ELISA as described in “Materials and methods.”