Prognosis in lymphoblastic leukaemia related to plasma mediated inhibition of incorporation of tritiated thymidine by transformed lymphocytes

The inhibitory effect of plasma from 20 consecutive untreated patients with lymphoblastic leukaemia (ALL) on phytohaemagglutinin (PHA) induced DNA-synthesis of normal homologous lymphocytes was assessed to determine whether the degree of inhibition had any relation to prognosis. Plasma from the patients, as a group, caused a significant reduction in incorporation of tritiated thymidine compared to healthy matched controls, and the 9 patients with the most inhibitory plasmas showed a median first remission length of only 6 months compared to over 3 y for the other 11. There was no association between the possession of strikingly inhibitory plasma and age or sex. There was, however, a marked correlation with the presence of a high white cell count, known to be associated with a poor prognosis in its own right. Even in the absence of a very high count, 4 4 of such patients who had marked inhibitory plasma proved to have refractory disease compared to only 4 10 of those with less inhibitory plasma. Consequently as an indicator of a poor outlook such inhibitory activity may be of value in ‘standard risk’ ALL.