Differences in the in Vitro Induction of Thymidine-3H Uptake into Leukemic Lymphoblasts by Phytohemagglutinin and Heterologous Antithymocyte Sera

Summary“Blast transformation” (increased in vitro uptake of thymidine-3H) of bone marrow lymphoblasts obtained from children with acute lymphoblastic leukemia (ALL) has been measured after the addition of either phytohemagglutinin (PHA) or rabbit anti-human thymocyte serum (ATS). Normal lymphocytes, or lymphocytes derived from patients with ALL in remission, show a significant increase in thymidine-3H uptake when cultured with either PHA or ATS. Bone marrow lymphoblasts from patients with ALL in relapse, on the other hand, showed a significant depression in the response to PHA whereas the response to ATS appeared unaffected. This differential response to in vitro stimulation suggests an alteration in the immunocompetence of bone marrow lymphoblasts in ALL.