Human MHC class I chain-related A (MICA) is a tumor-associated antigen that can be recognized by V delta 1 subset of tumor-infiltrating gamma delta T cells. We previously reported that immobilized recombinant MICA protein could induce the proliferation of tumor-infiltrating V delta 1 gamma delta T cells in vitro. But there has been no direct evidence showing the engagement of gamma delta T cell receptors (TCR) of the induced cells with MICA. In the current investigation, we show that MICA induces specific cytolytic activity of the expanded gamma delta T cells. We expressed the coupled V domains from the MICA-induced T cells as a single polypeptide chain V delta V gamma TCR (gamma delta scTCR). Such scTCR can specifically bind MICA of HeLa cells. Direct interaction of gamma delta scTCRs with in vitro expressed MICA was monitored using an IAsys biosensor. We found that the V delta 1 scTCR can specifically bind to immobilized MICA molecule and MICA alpha 1 alpha 2 domains are responsible for the binding reaction. (c) 2005 Elsevier Inc. All rights reserved.