Extracellular adenosine inhibits TCR-triggered CD25 upregulation on mitogen or anti-TCR/CD3 complex MoAb-activated T lymphocytes from normal DBA-2 mice. (A and B) Expression of CD25 on T lymphocyte from DBA-2 mouse splenocytes stimulated with con A (A) or with plate-bound antimouse CD3ε (B) for 8 hours. Expression of CD25 in the presence of adenosine alone is indicated by an arrow (a). Expression of CD25 in the presence of con A or anti-CD3 MoAb alone is indicated by an arrow (c). Expression of con A- or anti-CD3 MoAb-induced CD25 in the presence of adenosine is indicated by an arrow (b).