Chimeric receptors containing antibody-derived Fv or scFv as their extracellular recognition elements can redirect the specificity of T cells in an MHC-independent manner.

Upon encountering their target cells, such T-bodies are able to undergo specific stimulation for interleukin/cytokine production, and kill hapten-modified or tumor cells in both in vitro and in vivo model systems. T cells expressing chimeric receptors are able to discriminate between antigen-expressing and normal cells, with negligible bystander cytotoxicity. Unlike antibodies, T cells are well suited to penetrate and destroy solid tumors. Further in vivo studies should be carried out to evaluate and optimize the persistence, homing patterns, and reactivation potential of T-bodies in vivo.

Several technical obstacles must be overcome before this approach may be applied clinically. A most urgent problem is the low efficiency of T cell transfection techniques and the particular difficulty of transducing primary T cell populations. While retroviral-mediated gene transfer is more efficient than conventional techniques such as electroporation, the proportion of transfected cells remains low, necessitating an enrichment step. In addition, antibodies with improved discrimination between cell-bound and soluble forms of tumor antigens must be obtained to expand the repertoire of tumor antigens which may be targeted. For each antigen-antibody system, the optimal design of the scFv must be determined.

In the future application of this technology, the recognition element used for chimeric TCR is not limited to antibody-derived fragments [27]. Various ligands may be coupled to a T cell-triggering molecule in an attempt to redirect cytotoxic function towards target cells expressing a particular receptor molecule. Although still experimental, we feel that with fine tuning, the T-body approach shows promise as an efficient and broad-spectrum modality for tumor immunotherapy.