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Activation and death of lymphocytes in patients with oral cancer


γδ T cells play an important role as anti-tumor effector cells. However, their expansion is self-limiting. We investigated the activation induced cell death in γδ T cells after stimulation with heat shock proteins (hsp60, hsp70) that act as ligands for γδ T cells. Characterization of the molecular events in the apoptotic pathway revealed that nitric oxide (NO) is released by γδ T cells after hsp stimulation. Purified γδ T cells when incubated with rhsp60 and rhsp70 as well as artificial NO donors - SNAP and arginine, exhibited changes in mitochondrial membrane potential. Addition of caspase-9 inhibiting peptide Z-LEHD-FMK inhibited DNA fragmentation in γδ T cells and mitochondrial membrane potential changes, indicating involvement of caspases-9 in hsp60/70 induced apoptosis of γδ T cells. Our studies demonstrated a unique strategy adopted by tumor cells to evade immune recognition.

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