Hegen M, Mittrücker H W, Hug R, Demuth H U, Neubert K, Barth A, Fleischer B
First Department of Medicine, University of Mainz, Germany.
Immunobiology. 1993 Dec;189(5):483-93. doi: 10.1016/S0171-2985(11)80419-5.
CD26 is a proteolytic enzyme (dipeptidylpeptidase IV) expressed on the T cell surface that defines an alternative activation signal for human T lymphocytes. Crosslinking of CD26 via monoclonal antibodies triggers proliferation and cytotoxicity in preactivated T cells. In this study, we used highly specific competitive and irreversible inhibitors of dipeptidylpeptidase IV to study the role of the enzymatic activity in activation of CD26-transfected T cells as well as of CD26-expressing normal human T cell clones. These inhibitors at concentrations that blocked up to 95% of the enzymatic activity, did not specifically inhibit T cell activation neither via TCR/CD3 nor via CD26 itself. This demonstrates that the enzymatic activity of CD26 is not required for its T cell activating properties.
