tokens: The role of cytokine production by Vgamma1 ( + ) and Vgamma4 ( + ) T cells was investigated by adoptively transferring these cells isolated from H3-infected BALB/c Stat4 knockout ( Stat4ko ) ( defective in IFN-gamma expression ) or BALB/c Stat6ko ( defective in IL-4 expression ) mice into H3 virus-infected wild-type BALB/c recipients .