The Transfer RNA Methylases of Human Lymphocytes. II. Delayed Induction by PHA in Lymphocytes From Patients With Chronic Lymphocytic Leukemia

Treatment of lymphocytes from three patients with chronic lymphocytic leukemia (CLL) with phytohemagglutinin (PHA) resulted in a fivefold increase in transfer RNA (tRNA) methylase activity. Evidence was obtained which suggests that the increase included enzyme species not present prior to the induction. As with normal lymphocytes, the time of induction coincided with the formation of fully transformed PHA cells, which is markedly delayed compared with that occurring in normal lymphocytes stimulated with PHA. Although all three patients had an identical pattern of tRNA methylase induction, initial and induced absolute values were higher in the cells of one patient who had 10 per cent immature peripheral blood lymphocytes. The levels of transfer RNA methylase activity were similar in normal and CLL lymphocytes. These data suggest that PHA induces quantitative and qualitative changes in tRNA methylase enzymes of CLL lymphocytes similar to those previously reported in normal lymphocytes but that the sequence of events of PHA interaction with CLL lymphocytes leading to the subsequent enzyme induction is delayed.