In vitro radiosensitivity of human T and B lymphocytes evaluated using lymphocyte transformation tests and rosette formation tests.

The influence of irradiation upon human lymphocytes was studied using lymphocyte transformation tests and formation of E and HEAC rosettes. Irradiation was given in vitro using doses between 0 and 50,000 rad. It was shown that blast transformation after stimulation with T-cell stimulating agents (as PHA, PWM, Con.A and PPD) was suppressed by irradiation. The effect of irradiation upon T lymphocytes was also shown in different kinds of MLC experiments. Both the effect of irradiation upon rosetts formation and the influence of irradiation upon already formed rosettes were analyzed. The ability of lymphocytes to form E rosettes was affected after irradiation with 500 rad: there were fewer E rosettes with 3 SRBCs, decrease in total number of E rosettes and more null cells, with no depression of the number of HEAC rosettes formed. Already formed E and HEAC rosettes were totally unaffected of irradiation, and this radioresistance was also observed for 18-hour-old rosettes. The ability to form spontaneous E rosettes was decreased after irradiation of the lymphocytes with 100 rad; increasing doses did not cause further depression, and already formed spontaneous E rosettes were radioresistant. The mechanisms involved in E-rosette formation thus seem to be radiosensitive.