Alteration of membrane phospholipid methylation by adenosine analogs does not affect T lymphocyte activation

Membrane phospholipid methylation has been described during activation of various immune cells. Moreover recent data indicated modulation of immune cells functions by adenosine. As S-Adenosyl-methionine and S-Adenosyl-homocysteine are adenosine analogs and modulators of transmethylation reactions, the effects of SAH and SAM were investigated on membrane phospholipid methylation and lymphocyte activation. SAM (10(-5) M) was shown to induce the membrane phospholipid methylation as assessed by the 3H-methyl-incorporation in membrane extract. This effect was inhibited by SAH. In contrast SAM and SAH did not affect the phytohemagglutinin-induced proliferative response of peripheral blood mononuclear cells. SAH neither modified the early internalization of membrane CD3 antigens nor did it prevent the late expression of HLA-DR antigens on lymphocytes activated by phytohemagglutinin. These results indicate that in vitro alteration of phospholipid methylation does not affect subsequent steps of human T lymphocyte activation and proliferation.