Mechanism of interferon action. X--Antagonistic effect of ATP on pppA2'p5'A2'p5'A receptor.

pppA2'p5'A2'p5'A (2'-5'P3A3) receptor may be the first one in the oligonucleotide field. But ATP can compete with 2'-5'P3A3 for the receptor. This raises a question whether this is an ATP receptor. If not, what is the role of ATP for this receptor? Data available in this article show that ATP can bind to macrophages with saturability and reversibility. So ATP appears to be also a ligand of the receptor for 2'-5'P3A3. But the binding of ATP did not develop phagocytic effect as mentioned before. Moreover, ATP inhibited the enhancement of phagocytosis of macrophages by 2'-5'P3A3 when it acted together with 2'-5'P3A3 on macrophages at the same time. It is concluded that ATP is an antagonist of 2'-5'P3A3 receptor. When macrophages were treated with ATP prior to 2'-5'P3A3 and the binding sites for 2'-5'P3A3 were first occupied by ATP, both the binding ability and the binding sites for 2'-5'P3A3 were first occupied by ATP, both the binding ability and the biological effect of 2'-5'P3A3 were all markedly blocked. The above data convincingly show that the action of 2'-5'P3A3 is definitely mediated through its receptor.