The use of [125I]deoxyuridine for semi-microevaluation of human lymphocyte response to phytohemagglutinin in vitro.

[125I]5-iodo-2'-deoxyuridine ([125I]UdR) was compared with [6-3H]thymidine ([3H]TdR) in a semi-micromethod used to evaluate the response of human lymphocytes to phytohemagglutinin (PHA) in vitro. 5-Fluoro-2'-dexoyuridine (FUdR) was added to [125I]UdR in order to increase its incorporation, by preventing endogenous thymidine synthesis. The relationship between PHA concentration and the isotope uptake by lymphocytes was studied. Similar dose-response curves were found for the two precursors, with a peak at 15 microgram/ml of PHA. Nevertheless the recovery of the labeled compounds was higher when [125I]UdR together with FUdR was used.