Engineering antibodies to control T cell function

Antibodies have been used both to study T cells and in some instances, to control T cell function. However, therapeutic use of antibodies has been limited because of the side effects associated with antibody Fc regions and because of strong human-anti-mouse antibody responses. In an effort to overcome these difficulties, we have cloned and expressed the anti-T cell receptor (TCR) antibody KJ16 that recognizes the mouse TCR V;In Chapter Two, the purified scFv-KJ16 was shown to have an affinity for native TCR that was similar to Fab fragments. Monovalent forms of KJ16 and two other anti-TCR antibodies were used as probes to map the topology of TCR:ligand binding sites. The results of these studies led us to predict that the area on the TCR required to bind the superantigen/MHC is larger than the area required to bind the peptide/MHC.;In Chapter Three, a bispecific antibody that would redirect T cells to lyse folate-receptor-positive tumor cells was generated by directly coupling folate to scFv-KJ16. The folate/scFv conjugate was also successful in redirecting endogenous V;In Chapter Four, various forms of the KJ16 antibody were evaluated as inhibitors of T cell responses. Treatment with intact KJ16 but not F(ab);In Chapter Five, a yeast display system was used to show that a T cell receptor ligand (scFv-KJ16) expressed on the surface of yeast was capable of inducing T cell activation. These findings suggest that the yeast display system can be used to discover novel polypeptides that regulate biological functions through cell to cell interactions.