Dose-dependent effect of anti-CTLA-4 on survival in sepsis.

Cytotoxic T-lymphocyte antigen 4 (CTLA-4) is one of the critical inhibitory regulators of early stages of T-cell activation and proliferation, which opposes the actions of CD28-mediated costimulation. Anti-CTLA-4 therapy has been effective clinically in enhancing immunity and improving survival in patients with metastatic cancer. Sepsis is a lethal condition that shares many of the same mechanisms of immune suppression with cancer. Given the similarities in immune defects in cancer and sepsis, we examined the ability of anti-CTLA-4 antibody to block apoptosis, reverse the immunosuppression of sepsis, and improve survival in the cecal ligation and puncture model. Mice underwent sham or cecal ligation and puncture, and spleens harvested at various time points after surgery. Expression of CTLA-4 on CD4, CD8, and regulatory T cells was quantitated. Anti-CTLA-4 was administrated 6 and 24 h after surgery. Spleens were harvested at 48 h after surgery, and apoptosis and cytokine production determined. Seven-day survival studies were also conducted. Expression of CTLA-4 on CD4, CD8, and regulatory T cells increased during sepsis. Anti-CTLA-4 therapy decreased sepsis-induced apoptosis but had little effect on proinflammatory or anti-inflammatory cytokines. There was a dose-dependent effect of anti-CTLA-4 on survival. At high dose, anti-CTLA-4 worsened survival, but at lower doses, survival was significantly improved. Survival in sepsis depends on the proper balance between the proinflammatory and anti-inflammatory/immunologic systems. Anti-CTLA-4-based immunotherapy offers promise in the treatment of sepsis, but care must be used in the timing and dose of administration of the drug to prevent adverse effects.