EFFECT OF ACTINOMYCIN D ON RNA SYNTHESIS AND ANTIBODY FORMATION IN THE ANAMNESTIC RESPONSE IN VITRO.

Antibody synthesis in anamnestic lymphoid cells, measured by incorporation of leucine-C(14) into specific antibody, was inhibited at moderate concentrations of actinomycin D. This was accompanied by marked inhibition of synthesis of RNA as measured by incorporation of H(3)-cytidine monophosphate. However, at low concentrations of actinomycin D, antibody synthesis was unaffected or even increased while RNA synthesis continued to be inhibited. The results obtained suggest that messenger RNA for antibody synthesis, either because it is relatively stable or present in excess, does not become a limiting factor until its synthesis is maximally inhibited. Puromycin, an inhibitor of amino acid coupling, abolished antibody synthesis in low concentration. 6-Mercaptopurine had no effect on the synthesis of antibody or RNA even at high concentration. The data obtained support the view that antibody synthesis follows pathways similar to those utilized for the formation of other types of proteins.