Progress in experimental pathology in the People's Republic of China. Action of pppA2'p5'A2'p5'A on the immune system.

Enhancement of phagocytosis of macrophages and the activity of natural killer cells by pppA2'p5'A2'p5'A (2'-5'P3A3) has been described. During the action of 2'-5'P3A3 on these immune cells, neither CaCl2 nor other agents were used to introduce 2'-5'P3A3 into the cells. The action of 2'-5'P3A3 on macrophages might be mediated by a surface receptor for 2'-5'P3A3. This is the first report of an oligonucleotide that confers biological action through a receptor. Activation of the immune system by 2'-5'P3A3 without using the agents like CaCl2, and the discovery of a 2'-5'P3A3 receptor in macrophages suggest that 2'-5'P3A3 and its derivatives may have some practical use.