Effect of antiserum on leukemia L5178Y cells: [3H]thymidine incorporation does not reflect DNA synthesis.

1. The total amount of DNA present in L5178Y cells treated with antiserum in the absence of complement was decreased whereas the rate of incorporation of [3H]thymidine into DNA during a 1 hr pulse was increased as compared with those of controls. 2. This increase in specific activity of [3H]thymidine in the DNA of antiserum-treated cells appeared to be due, at least in part, to an increase in thymidine kinase activity.