Long-term effects on the immune system following local irradiation for breast cancer. Pokeweed mitogen induced immunoglobulin secretion by blood lymphocytes and serum immunoglobulin levels.

Previous studies have shown that the PWM driven immunoglobulin (Ig) secretion by blood lymphocytes in vitro is reduced shortly after local radiation therapy for breast cancer. In this investigation we have examined the long-term effects of radiation therapy (45 Gy) on this lymphocyte function. A total of 111 disease-free patients treated for operable breast cancer 5-6 and 10-11 years earlier were examined. The Ig classes studied were IgM, IgA and IgG. All patients belonged to a clinical trial where the effect of pre- or post-operative local radiation therapy was evaluated against surgery only. Significant reductions of the amount of spontaneously released IgM in vitro were observed among irradiated patients as compared to the unirradiated 5-6 and 10-11 years after treatment. Such a difference was not observed for IgA and IgG. The PWM induced Ig secretions did not differ significantly between the three patient groups. The long standing reduction of the spontaneous release of IgM by blood lymphocytes in vitro probably lacks clinical significance since the serum levels of this Ig class, as well as IgA and IgG, were similar in irradiated and unirradiated patients.