Mechanisms Underlying Antigen-Specific CD8 ⁺ T Cell Homeostasis

Badovinac et al. (1) reported important new insights concerning the role of perforin and interferon-γ (IFN-γ) in regulating antigen-specific (Ag-specific) CD8+ T cell homeostasis. Using an attenuated strain ofListeria monocytogenes, they demonstrated that absence of perforin resulted in increased levels of specific CD8+ T cells, whereas absence of IFN-γ contributed to altered immunodominance hierarchies and to a reduced death phase of the CD8+ T cell population following acute infection. Based on these experimental results, it was argued that regulation of specific CD8+ T cell homeostasis by perforin and IFN-γ is brought about by a mechanism that is independent of the role of these effectors for controlling the infection.