EFFECTS OF INHIBITION OF RIBOSOMAL RNA SYNTHESIS ON STIMULATION OF LYMPHOCYTES BY PHYTOHAEMAGGLUTININ

Low concentrations of actinomycin inhibit the synthesis of ribosomal RNA preferentially in stimulated human lymphocytes. When ribosomal RNA synthesis was completely inhibited in this fashion there was still a substantial stimulation of the rate of lymphocyte protein synthesis by PHA, and persistence of some of the morphological changes typical of transformation. However, inhibition of ribosomal RNA synthesis was associated with inhibition of DNA synthesis and mitosis in lymphocytes incubated with PHA. Although these phenomena may be coordinately regulated, it is suggested that the low ribosome level may be an important factor preventing DNA synthesis, and thus cell division, by lymphocytes. © 1969.