The superantigen SEA binds to human γδ T cell receptor and activates γδ T cells with moderate MHC class II dependence

Abstract

Bacterial toxins, called superantigens, are produced by Staphylococcus aureus and are known to activate γδ T cells. γδ T cells contribute to long-lasting immunity against bacterial skin infections caused by S. aureus. γδ T cells are a distinct subgroup of T cells containing the T cell receptor (TCR) γ and δ chains. The γδ TCR harbouring the variable chains TRGV9/TRDV2 is the most common TCR in human peripheral blood and is known to be activated by superantigens and are also promising candidates for tumor immunotherapy. However, detailed analyses of antigen binding to γδ TCR have been severely hampered by difficulties in producing large amounts of γδ TCR. In this study, we report a protocol to produce recombinant γδ TCR (TRGV9/TRDV2) by fusing the variable domains γδ TCR with the constant domains of αβ TCR. Subsequently, binding analyses were executed applying microscale thermophoresis showing a clear binding between superantigen and the γδ TCR in the micro molar range. In addition, the superantigen SEA was shown to induce cytokine expression in γδ T cells with moderate MHC dependence, suggesting that other receptors can act as antigen presenting molecules upon γδ T cell activation. These results pave the way towards a better understanding of superantigen recognition by the γδ T cells and facilitates the future use of γδ TCR in cellular tumor immunotherapy.

Keywords: SEA; Superantigen; TRGV9/TRDV2; Unconventional T cell receptor; γδ TCR.