The present disclosure relates to non-natural NKG2D receptors attached to mammalian cell surfaces wherein the non-natural receptors do not directly signal or directly activate the cell when the receptor is bound by cognate non-natural α1-α2 domains of NKG2D ligands modified to specifically bind the non-natural NKG2D receptors. The non-natural α1-α2 domains of NKG2D ligands may be attached to heterologous atoms or molecules including polypeptides, in some embodiments cytokines or modified cytokines, antibodies or fragments of antibodies.
