Tho DIFFERENTIATION TO Th1 or Th2 CELL VIRUS L-12 NK CELL DENDRITIC CELL IL-2 Th1 IFN-gamma IFN-gamma L-12 L-2 L-4 Tho IFN-gamma CD4 T CELL L-4 Th2 L-5 L-6 CD4 T,NK1.1+ EXTRACELLULAR PATHOGEN