Effect of balanced inhibition of DNA and protein synthesis on proliferative activity of lymphocytes in vitro and in vivo

Lymphocytes isolated from the peripheral blood of rabbits were irradiated in vitro in doses of 200, 400, and 1000 R and cultured with phytohemagglutinin (PHA) at 37°C for 48 h. In separate experiments 60 min before and 30 min after irradiation the cells were treated with cycloheximide, an inhibitor of protein synthesis, but this had no significant effect on survival of the irradiated cells. The ability of lymphocytes from the popliteal lymph nodes of the irradiated mice to proliferate after injection of PHA into the footpad of one hind limb also was investigated. Injection of cycloheximide or puromycin into the footpad of one hind limb immediately after irradiation of the animals increased the proliferative activity of lymphocytes from the lymph nodes of that limb by 50–100% compared with the contralateral limb. Cytosine arabinoside, an inhibitor of DNA synthesis was ineffective under these conditions.