Enhanced Antibody and Cytokine Responses to Influenza Viral Antigens in Perforin-Deficient Mice

Cytotoxic T lymphocytes (CTL) lyse virus-infected target cells by secreting the pore-forming effector molecule, perforin. Perforin-mediated cell death appears to be a major mechanism in viral clearance but its role in regulating immune responsesin vivois unclear. In this report, we show that following immunization with influenza viral antigens, perforin-deficient mice generated about 100-fold greater serum antibody responses than wild-type mice. Further, immune spleen cells from perforin knock-out mice secreted over 10-fold more IFN-γ followingin vitrorestimulation than immune spleen cells from control mice. Finally, there were over 10-fold more IFN-γ-secreting cells in cultures from perforin-deficient mice than those from control mice, suggesting that the enhanced cytokine release by T cells from perforin-deficient mice is due to an increase in the effector cell pool. Collectively, these results suggest that perforin-mediated effector function is required in the down-regulation of the immune response by way of limiting antigen-presenting cell function.