Activation of T cells via tumor antigen specific chimeric receptors: The role of the intracellular signaling domain

T cells engineered to express hybrid receptors with antibody defined specificity can successfully be targeted to tumor cells. In order to select intracellular domains of chimeric receptors capable of efficiently activate T cells in vitro and in vivo , we compared the function of receptors, which share the same extracellular antigen‐binding part, joined to different intra‐cellular signal transduction units. The antigen binding domain of the receptors was a single‐chain fragment of a monoclonal antibody, which recognize a High Molecular Weight Melanoma‐Associated Antigen with high affinity. The intracellular tails were derived from the T‐cell receptor ζ chain (TCR‐ζ), from the B‐cell receptor Ig‐α molecule and from a mutated Ig‐α molecule able of stronger signal transduction. We compared the activity of the different chimeric receptors at a single‐cell level by using a T‐cell line that expressed an activation‐dependent EGFP‐reporter gene. Upon cross‐linking with immobilized antibodies, all receptors were able to induce EGFP expression in the majority of the T cells. In contrast, EGFP expression was induced by contact to melanoma cells in vitro only in T cells that expressed the chimeric receptor that contained the TCR‐ζ intracellular tail. In these T cells, the co‐expression of chimeric receptors that contain a mutated Ig‐α tail lowers the threshold of T‐cell activation and facilitates tumor recognition in vitro and in vivo . Given their specificity and efficiency, T cells grafted with these type of receptors may represent potential candidates for cancer passive immunotherapy. © 2002 Wiley‐Liss, Inc.