Anti-GITR treatment improves T-cell–dependent antibody responses in septic mice. C57Bl/6 mice underwent a sham procedure or cecal ligation and puncture (CLP) surgery and were immunized subcutaneously with the T-cell–dependent antigen NP-KLH and alum. Ten days later, serum (A) IgM, (B) IgG_2a, and (C) IgG₁ anti-NP antibody responses were measured by ELISA and compared with baseline samples. In another experiment, C57Bl/6 mice were given an intraperitoneal injection of 300 μg control antibody (Sham and CLP groups) or anti-GITR antibody and underwent cecal ligation and puncture or sham treatment 30 minutes later. Immediately following, mice were immunized with NP-KLH and alum. Ten days later, mice were bled and anti-NP–specific IgM (A), IgG_2a (B), and IgG₁ (C) were measured from the serum. P values indicate the difference between groups after immunization by Student t test (A-C) or post hoc analysis using Fisher LSD method (D-F).