Binding of adenosine deaminase to the lymphocyte surface via CD26.
The 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 ADA to CD26.
De Meester
I
I
Department of Clinical Biochemistry, University of Antwerp, Wilrijk, Belgium.
Vanham
G
G
Kestens
L
L
Vanhoof
G
G
Bosmans
E
E
Gigase
P
P
Scharpé
S
S
D000243:Adenosine Deaminase / Q000378:metabolism*; D016525:Antigenic Modulation; D000945:Antigens, Differentiation, T-Lymphocyte / Q000378:metabolism*; D018819:Dipeptidyl Peptidase 4; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D016131:Lymphocyte Subsets / Q000201:enzymology*; D011485:Protein Binding
D000945:Antigens, Differentiation, T-Lymphocyte; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; D018819:Dipeptidyl Peptidase 4; D000243:Adenosine Deaminase