Increased levels of interferon-induced (2'--5') oligo-isoadenylate synthetase in mature T-lymphocytes and in differentiated Friend-erythroleukemic cells.

The level of (2'--5') oligo-isoadenylate synthetase was measured in lymphocytes at different stages of maturation within the T cell lineage and in Friend-erythroleukemic cells induced to differentiate by 1.5% Me2SO. The level of (2'--5') oligo-isoadenylate synthetase was higher in the peripheral mature T-lymphocytes than in the thymocytes. Further fractionation of the thymic population by peanut agglutinin showed higher levels of the synthetase activity in the mature PNA- cells than in the immature PNA+ cells. The activity of the enzyme in the immature thymic subpopulation could be stimulated in vitro after treatment with interferon. On the other hand, these cells did not produce the mitogen-induced immune interferon (gamma-type). Human peripheral mononuclear cells exhibited high levels of the (2'--5') oligo-isoadenylate synthetase, as well as the leukemic cells from patients with chronic lymphatic leukemia; extremely low levels of the enzyme were detected in some of the patients with acute lymphatic leukemia. In cultures of Friend cells, induced to differentiate by Me2SO, the level of the (2'--5') oligo A synthetase was low in rapidly growing cells and increased by a factor of 8--10 as the cells reached the stationary phase. This increase was completely prevented if anti-interferon antiserum was added to the medium concomitant with the Me2SO, suggesting that the increase in the level of (2'--5') oligo A synthetase is mediated by secretion of interferon by the cells. The inhibition of induction of the synthetase during differentiation, caused by the antiserum, was accompanied by a reduction in hemoglobin accumulation, whereas adding (2'--5') ApApA core to the cells together with Me2SO increased slightly hemoglobin accumulation.