TRAIL regulates DTH in naive and sensitized CLP mice. A, Trail−/− or Trail+/+ (C57BL/6 littermates) were subjected to CLP or sham surgery. Four days postsurgery, mice were immunized s.c. with TNBS. After an additional 4 d, mice were challenged with TNBS in the right and PBS in the left footpad. B, Trail−/− or Trail+/+ (C57BL/6 littermates) were immunized s.c. with TNBS. Four days later, they were subjected to CLP. After an additional 3 d, they were challenged with TNBS in the right and PBS in the left footpad. Measurements (μm ± SE) were taken 24 h later and represent the difference between right (Ag challenge) and left footpad (PBS challenge). The data are reported as immune response to TNP and are compared with an immune control that received only s.c. immunization. *Significant difference from immune control mice measured on the same day (p < 0.01).