CD26 ANTIGEN IS A SURFACE DIPEPTIDYL PEPTIDASE-IV (DPPIV) AS CHARACTERIZED BY MONOCLONAL-ANTIBODIES CLONE TII-19-4-7 AND 4EL1C7

In this study we investigated the binding or three different monoclonal antibodies (MoAb), TII 19‐4‐7,4EL1C7, and B1.19.2, which are clustered in CD26 to the ectoenzyme dipeptidyl peptidase IV (DPP IV) and to T lymphocytes. We found that all three MoAb bind to both unstimulated and mitogen‐stimulated T lymphocytes. Further results indicated an inconsistency within the CD26‐clusteredMoAb: TII 19‐4‐7 and 4EL1C7, but not Bl.19.2, recognized DPP IV on the surface of T lymphocytes and immobilized on solid‐phase ELISA or Western blot. There was compelition of binding to DPP IV between TII 19‐4‐7 and 4ELIC7. From these results we conclude that CD26 antigen is represented by the ectoenzyme DPP IV. TII 19‐4‐7 and 4ELIC7 recognize the same or partly identical epitopes on DPP IV, whereas B1.19.2 recognizes a different antigen. TI I 19‐4‐7 and 4ELlC7, but not B1.19.2, should be clustered in CD26. Copyright © 1990, Wiley Blackwell. All rights reserved