Adenosine 5'-triphosphate- (ATP) mediated stimulation and suppression of DNA synthesis in lymphoid cells. I. Characterization of ATP responsive cells in mouse lymphoid organs

The effects of various nucleotides and nucleosides on DNA synthesis of mouse lymphocyte populations were studied. Significant stimulation of DNA synthesis was observed in the cells from bone marrow or the thymus in the presence of ATP. In contrast, the DNA synthesis of the cells from spleen, lymph nodes, and peripheral blood was markedly inhibited by ATP. Guanosine 5'-triphosphate had nonspecific stimulatory effects on the DNA synthesis of various lymphoid cells, whereas cytidine triphosphate had no effect. When thymocytes or bone marrow cells were separated by 1 x g velocity sedimentation, a distinct cell population was identified as being responsible for the ATP-mediated stimulation of DNA synthesis. Further characterization of ATP-responsive cells revealed that the highest concentration of terminal deoxynucleotidyl transferase, a marker enzyme for precursor T cells, was present in these cells. ATP-mediated stimulation of DNA synthesis may therefore, serve as a specific marker restricted to a certain population of differentiating T cells.