Inhibitory effect of autologous plasma on the uptake of tritiated thymidine by leukaemic lymphoblasts and its relation to prognosis.

In vitro incorporation of tritiated thymidine was measured in blast cells from 33 unselected and untreated patients with lymphoblastic leukaemia (ALL) both when autologous plasma was present and also when it was substituted by pooled normal plasma. A similar procedure was carried out on 19 patients with acute non-lymphoblastic leukaemia (AnonLL). Plasma from the patients with ALL was variably found to reduce the uptake of the radiolabelled DNA-precursor by their own blasts, with the most marked effect apparent in those with shorter survival times (P < 0.02). This phenomenon was not observed in AnonLL. The amount of plasma-mediated inhibition shown by the ALL patients also correlated overall with their WBC, a known feature of a poor outlook, but even in the 21 patients with WBC below 20.0 x 10(9)/l there was still a significant association between plasma effect and survival (P < 0.01). The demonstration of such inhibitory plasma may be a useful prognostic marker in otherwise 'standard risk' ALL, and also may indicate a large tumour mass where this is not reflected by the height of the circulating WBC.