CD8A and cancer: For example, adjuvants that lead to a poor Th1- or CTL- or Th2-biased immune response are inappropriate for use as cancer vaccine adjuvants, because robust tumor-specific CD8+ CTLs are required for the effective anti-cancer therapies; memory Th1 cells can augment tumor-specific CTL responses, whereas Th2 cells favor tumor growth by inhibiting Th1 immunity [48,49,50].