Fig. 2

Cartoon overview of γδ T cells receptor-dependent interaction with influenza virus or influenza-virus-infected respiratory cells. a Activation of γδ T cells by the interaction between NKG2D (natural killer group 2D) receptor of γδ T cells with its ligands, MHC class I chain-related sequence A and B (MICA and MICB), expressed on the surface of influenza-infected epithelial cells, inducing the release of some cytokines and cytolytic proteins, somehow halting the influenza infection. b The interaction of influenza haemagglutinin (HA) on the surface of influenza viruses with sialic acid receptors plays a key role in the activation of γδ T cells, triggering the production of interferon-γ (IFN-γ). c γδ T cells utilize TNF-related apoptosis inducing ligand (TRAIL) for killing of influenza-infected cells. Infected epithelial cells express death receptors TRAIL-R1 or TRAIL-R2, identifying their ligand (Apo2 ligand) on the surface of influenza infection-activated γδ T cells and undergo apoptosis through Caspase-dependent pathways. d) FAS ligand expressed by γδ T cells, when exposed to FAS receptor available on influenza-infected cells surface activates the pathway of FAS-FASL apoptosis to destroy the infected cell