Finally, it is interesting to note that STAT3-dependent cytokines, such as IL-6, IL-10, and IL-21, as well as MyD88-dependent IL-1 have been suggested to play a role in memory CD8+ T cell differentiation and functional maturation following immunization and infection (Foulds et al., 2006; Hinrichs et al., 2008; Castellino and Germain, 2007; Cui et al., 2011; Yi et al., 2010). The gene discussed is IL21; the disease is infection.