Experiments using in vitro stimulated T cells (Kaech and Ahmed, 2001), antibiotic treatment prior to Listeria monocytogenes or influenza co-infection (Badovinac et al., 2004), dendritic-cell vaccination (Badovinac et al., 2005), clonal dissection of influenza-specific CD8+ T cells at different stages of infection (Kedzierska et al., 2006, 2008) or transfer studies (Kedzierska et al., 2007) suggest that the full expansion to effector status is not a pre-requisite for the generation of long-term memory T cells. The gene discussed is CD8A; the disease is infection.