Binding of adenosine deaminase to the lymphocyte surface via CD26

摘要

AbstractThe relationship between CD26/dipeptidyl peptidase IV, an ectopeptidase involved in T cell activation, and the binding protein for adenosine deaminase (ADAbp) was studied. Monoclonal antibodies (mAb) against CD26 and ADAbp, respectively, showed a similar binding profile on various lymphocyte subsets from the peripheral blood. The adenosine deaminase (ADA) itself blocked the binding of a specific set of anti‐CD26 mAb (among these the anti‐TA5.9 mAb) on lymphocytic CD26; ADA also hindered the binding of soluble CD26 to the same immobilized anti‐CD26 mAb. In addition, the interaction between immobilized ADA and purified CD26/DPP IV was inhibited by the anti‐TA5.9 mAb. ADA did not inhibit the specific peptidase activity of CD26. Neither soluble nor immobilized ADA was able to down‐modulate CD26 on the lymphocyte surface. Our data thus confirm the identity between ADAbp and CD26 and identify some epitopes, crucial in the binding of AD