PRF1 and influenza: Here, we generated streptavidin-conjugated human CD137L protein and demonstrated that recombinant SA-hCD137L could promote the cytolytic effector function of Vγ9Vδ2-T cells against influenza-infected MDMs by promoting the release of cytolytic granules (containing perforin and granzyme B) and an antiviral cytokine (IFN-γ) from Vγ9Vδ2-T cells, suggesting that SA-hCD137L offers a compelling alternative to anti-CD137 agonistic antibody-mediated stimulation for influenza immunotherapy.