PDCD1 and influenza: Treatment with an anti-PD-1 antibody was shown to increase NY-ESO-1-specific CD8+ T cells expansion in melanoma patients and in contrast to EBV, influenza, or Melan-A/MART-1-specific CD8+ T cells, NY-ESO-1-specific CD8+ T cells uniquely express the PD-1 molecule (26).