Autoradiographic Studies of Nucleic Acid and Protein Metabolism in Lymphoid Cells

Summary In vitro studies with antibody‐producing cells in culture showed that blast cells were much more active in continuous incorporation of the RNA precursor, 3 H‐uridine, than were either mature plasma cells or small lymphocytes. After one hour of incubation, blast cells had incorporated more than 100 times the amount of labelled uridine taken up by plasma cells. Nuclease‐digested smears showed that in blast cells, nuclear RNA was rapidly labelled, while there was a slower rise in labelled cytoplasmic RNA and nuclear DNA. No DNAase‐sensitive incorporation was detected in small lymphocytes or mature plasma cells. Despite their low uptake of labelled uridine, mature plasma cells showed active protein synthesis at about 70 per cent the level of blast cells. The ratios of uridine uptake per mole of lencine incorporated by mature phasma cells were: blasts, 93; small lymphocytes, 8; mature plasma cells, 1. This indicated the lack of dependence of protein synthesis in mature plasma cells on concomitant RNA synthesis.