Increased Levels of Interferon-induced (2′–5′) Oligo-Isoadenylate Synthetase in Mature T-Lymphocytes and in Differentiated Friend-Erythroleukemic Cells

Abstract

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 (γ-type). Human peripheral monunuclear 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′) olgio 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.