Another recent study dissected the efficacy of CD8+ T cells in protecting against pulmonary Yersinia pestis infection, showing that TNF-α and IFN-γ effector molecules were crucial for in vivo protection, whereas perforin-driven cytotoxicity was not.[7] The previous study elegantly demonstrated the feasibility and importance of identifying the effector molecules contributing to T cell efficacy, however their use of mouse knock-out models to discern important versus non-important effector molecules is laborious and non-applicable to human studies. This evidence concerns the gene TNF and plague.