Southern blot analyses indicate that the T-cell receptors of alloreactive T-cell lines derived from needle biopsies of human kidney allografts are selected based on β-chain usage. In order to examine this selection at the level of T-cell-receptor expression, we have generated monoclonal antibodies directed toward the T-cell-receptors of three allograft-derived T-cell lines, MH3, WP3, and EH3. Monoclonal antibodies have been isolated which appear to react specifically with each of these three T-cell lines. One anti-MH3 antibody precipitates a molecule from the surface of MH3 cells that comigrates with the α/β TcR on a polyacrylamide gel. Te WP3 reactive monoclonal antibodies were identified which are cause a modulation of CD3 from the surface of WP3 T cells, although none as yet precipitates a molecule from lysates of surface 125I-labeled WP3 cells. Since Northern blot analysis of EH3 RNA has revealed that a member of the Vβ6 gene family is expressed by this T-cell line, we are attempting to identify a monoclonal antibody reactive with this Vβ6 gene product.