Stimulation of DNA synthesis in mouse lymphoid cells by polyanions in vitro. I. Target cells and possible mode of action

The effect of dextran sulfate on [³H]dThd incorporation in lymphoid cells was investigated. The polyanion activated DNA synthesis in spleen and bone marrow cells of normal mice. The highest rate of activation was detected in spleen cells of athymic (nude) mice; the ratio of [³H]dThd incorporation was higher in TxBM spleen cells of thymectomized, lethally irradiated and bone marrow protected mice than in spleen cells of normal donors. Thymus cells of normal mice could not be stimulated, but a slight response was obtained in cortisone-resistant thymus cells. A synergetic effect was found in normal thymus cells using a combination of dextran sulfate and phytohemagglutinin (PHA). In contrast, lipopolysaccharide and PHA showed no synergetic effect. The possible mode of action of polyanions as de-repressors of DNA synthesis is discussed.