Effect of cyclic adenosine monophosphate on the in vitro DNA synthesis in lymphocytes of patients with chronic lymphocytic leukemia.

Deoxyribonucleic acid (DNA) synthesis was investigated in vitro in T and B lymphocyte populations isolated from peripheral blood. The synthesis was determined by measurements of 3H-thymidine incorporation. Only T lymphocytes isolated from peripheral blood of healthy subjects as well as patients with chronic lymphocytic leukemia (cll) showed proliferative ability after stimulation with phytohemagglutinin (PHA). DNA synthesis rate in normal T lymphocytes was enhanced by exogenous cyclic adenosine monophosphate (cAMP) added to lymphocyte culture together with PHA in concentrations of 10(-5) and 10(-4)M. Higher concentrations (10(-3) and 10(-2)M) of this nucleotide inhibited DNA synthesis in the lymphocytes of healthy subjects as well as cell patients. Impairment of 3H-thymidine incorporation observed in cll (in non-isolated cell populations) seems to be due to the presence of non-proliferating lymphocyte B population.