Intracellular single chain Fv antibody inhibits Ras activity in T-cell antigen receptor stimulated Jurkat cells.

A mammalian expression vector directing the synthesis of a cytoplasmic single chain Fv version of the Y13-259 anti-Ras antibody was constructed and co-transfected into the human lymphoid cell line Jurkat together with a reporter construct containing the bacterial gene for chloramphenicol acetyl transferase under the transcriptional control of several copies of the binding site for the transcription factor NF-AT. The Ras specific antibody interferes with NF-AT activation upon direct activation of the T-cell antigen receptor, whereas activation by direct protein kinase C stimulation is less sensitive to the anti-Ras antibody. Furthermore, the observed inhibition is dependent on the ratio of antibody to reporter plasmid utilized in the transfection experiments.