M. Hegen et al., ENZYMATIC-ACTIVITY OF CD26 (DIPEPTIDYLPEPTIDASE IV) IS NOT REQUIRED FOR ITS SIGNALING FUNCTION IN T-CELLS, Immunobiology, 189(5), 1993, pp. 483-493
CD26 is a proteolytic enzyme (dipeptidylpeptidase IV) expressed on the
T cell surface that defines an alternative activation signal for huma
n T lymphocytes. Crosslinking of CD26 via monoclonal antibodies trigge
rs proliferation and cytotoxicity in preactivated T cells. In this stu
dy, 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 bl
ocked up to 95 % of the enzymatic activity, did not specifically inhib
it T cell activation neither via TCR/CD3 nor via CD26 itself. This dem
onstrates that the enzymatic activity of CD26 is not required for its
T cell activating properties.