Single domain intrabodies against WASP inhibit TCR-induced immune responses in transgenic mice T cells.

Intrabody technology provides a novel approach to decipher the molecular mechanisms of protein function in cells. Single domains composed of only the variable regions (V(H) or V(L)) of antibodies are the smallest recombinant antibody fragments to be constructed thus far. In this study, we developed transgenic (Tg) mice expressing the V(H) or V(L) single domains derived from a monoclonal antibody raised against the N-terminal domain of Wiskott-Aldrich syndrome protein (WASP), which is an adaptor molecule in immune cells. In T cells from anti-WASP V(H) and V(L) single domain Tg mice, interleukin-2 production induced by T cell receptor (TCR) stimulation were impaired, and specific interaction between the WASP N-terminal domain and the Fyn SH3 domain was strongly inhibited by masking the binding sites in WASP. These results strongly suggest that the V(H)/VL single domain intrabodies are sufficient to knockdown the domain function of target proteins in the cytosol.