Recruit or Reboot? How Does Anti-PD-1 Therapy Change Tumor-Infiltrating Lymphocytes?

It has been widely assumed that PD-1 blockade works by reinvigorating (rebooting'') pre-existing exhausted tumor-infiltrating ilymphocytes (TILs). A recent study challenges this paradigm, demonstrating that the majority of tumor-specific TILs after anti-PD-1 treatment have TCRs not identified in the tumor pre-therapy, suggesting they are newly recruited post-therapy.