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The Costimulatory Activity of the CD26 Antigen Requires Dipeptidyl Peptidase IV Enzymatic Activity

Toshiaki Tanaka, Junichi Kameoka, Arieh Yaron, Stuart F. Schlossman and Chikao Morimoto
Proceedings of the National Academy of Sciences of the United States of America
Vol. 90, No. 10 (May 15, 1993), pp. 4586-4590
Stable URL: http://www.jstor.org/stable/2362123
Page Count: 5
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
The Costimulatory Activity of the CD26 Antigen Requires Dipeptidyl Peptidase IV Enzymatic Activity
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Abstract

T cells have been shown to express CD26, a known ectoenzyme with dipeptidyl peptidase IV (DPPIV; EC 3.4.14.5) activity in its extracellular domain. CD26 can also deliver a second costimulatory signal and contribute to T-cell activation. In an earlier study, we established CD26-transfected Jurkat T-cell lines and demonstrated that monoclonal antibody-mediated crosslinking of CD26 and CD3 induced interleukin 2 (IL-2) production. To determine the contribution of DPPIV enzymatic activity to the costimulatory activity of CD26, human CD26 cDNA was mutated so that active-site serine was replaced by alanine. The mutant CD26 antigen lacked DPPIV enzyme activity but still retained reactivity with three anti-CD26 monoclonal antibodies directed against distinct epitopes of CD26. After stimulation with a combination of anti-CD26 and anti-CD3 antibodies, wild-type CD26 (DPPIV+)-transfected Jurkat cells produced substantially more IL-2 than did mutant CD26 (DPPIV-) or CD26- control transfectants. Nevertheless, the mutant CD26-transfected cells still produced significantly more IL-2 than did CD26- control transfectants. These results suggest that DPPIV activity plays an important but not absolute role in the costimulatory activity of CD26 in this system. We also found that wild-type CD26 (DPPIV+) transfectants produced more IL-2 than mutant CD26 (DPPIV-)-transfected cells or CD26- control transfectants when triggered by stimuli not involving CD26, such as anti-CD3 and phorbol ester. These results suggest that the DPPIV activity of CD26 functions to augment the cellular responses of CD26-transfected Jurkat cells to external stimuli mediated by CD26 and/or the CD3/T-cell receptor complex, thus enhancing IL-2 production.

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