Uridine does not reverse inhibitory effects of adenosine on TCR-triggered CD25 upregulation. (A) CD25 levels were evaluated on T lymphocytes from DBA-2 mouse splenocytes that were stimulated with 4 μg/mL con A for 8 hours in the presence (arrow b) or absence (arrow c) of 200 μmol/L uridine. Arrow a represents the level of CD25 in the unstimulated cells with or without uridine. (B) Inhibition of con A-induced CD25 expression of 100 μmol/L adenosine is not reversed by the presence of uridine. Arrow a shows the inhibited expression of CD25 in con A-stimulated cells in the presence of both adenosine and uridine. Arrow b shows the inhibited expression of CD25 in con A-stimulated cells in the presence of adenosine. Arrow c shows the expression of CD25 in con A-stimulated cells in the absence of both adenosine and uridine. No coformycin or NBTI was used in this experiment. NBTI was omitted to allow the transport of uridine across cell membranes.