Radiation effects on human lymphocytes stimulated by phytohemagglutinin

Looking beyond COVID-19 vaccine phase 3 trials

After the recent announcement of COVID-19 vaccine efficacy in clinical trials by several manufacturers for protection against severe disease, a comprehensive post-efficacy strategy for the next steps to ensure vaccination of the global population is now required. These considerations should include how to manufacture billions of doses of high-quality vaccines, support for vaccine purchase, coordination of supply, the equitable distribution of vaccines and the logistics of global vaccine delivery, all of which are a prelude to a massive vaccination campaign targeting people of all ages. Furthermore, additional scientific questions about the vaccines remain that should be answered to improve vaccine efficacy, including questions regarding the optimization of vaccination regimens, booster doses, the correlates of protection, vaccine effectiveness, safety and enhanced surveillance. The timely and coordinated execution of these post-efficacy tasks will bring the pandemic to an effective, and efficient, close.

X-irradiation of equine peripheral blood lymphocytes stimulated with phytohaemagglutinin in vitro

Small lymphocytes were isolated from the peripheral blood of horses and incubated at 37 degrees C in Eagle's medium supplemented with 20 per cent foetal calf serum. The addition of phytohaemagglutinin (PHA) to the cultures resulted in: increased RNA and protein synthesis; the enlargement of the small lymphocyte into a lymphoblast-like cell; the initiation of DNA synthesis, and cell division. When survival was measured 24 hours after X-irradiation by means of phase-contrast microscopy, the lymphoblast-like cell was much more radio-resistant (D0 = 250 rad) than the small lymphocyte (D0 = 20 rad). This increase in radioresistance, however, was not observed until 12-24 hours after PHA treatment. To investigate which of the changes occurring during the transformation of the small lymphocyte was responsible for the increased resistance to irradiation, the percentage of cells surviving irradiation was compared with the percentage of cells incorporating significant amounts of 3HTdR, 3H-UR, or 3H-leucine at the time of irradiation. For this comparison, a dose of 100 rad was used because 100 rad killed essentially all of the small lymphocytes, but less than 35 percent of the cells which had become radioresistant from the PHA treatment. The results indicated that the increase in radioresistance was not associated with DNA synthesis, but instead correlated with the increase in RNA and protein synthesis which the cells had attained at the time of irradiation.