IL-4 can induce the activation of STAT1, STAT3, STAT5 and STAT6 on naïve and activated CD8+ T cells in vitro[29], but our infections studies with VV-HA-IL-4 indicated that STAT6 was indispensible for IL-4 mediated up-regulation of cell surface IL-4Rα expression on naïve and effector CD8+ T cells. Here, STAT1 is linked to infection.