Prostaglandin sensitivity of the PHA-response of blood lymphocytes following radiation therapy for breast cancer.

The reduction of mitogen responses of blood lymphocytes which occur after radiation therapy for breast cancer, known to be largely due to inhibitory monocytes, can partly be reverted by indomethacin which is an inhibitor of prostaglandin (PG) synthesis. This may indicate that PG-synthesis by blood monocytes is increased after irradiation or that PG-sensitivity of the lymphocyte population is increased. To test the latter possibility the sensitivity of the PHA-response of blood lymphocytes to varying concentrations of PGE2 and PGD2 was examined in 15 patients with breast cancer before and up to 6 months after local radiation therapy (46 Gy). The results showed that the sensitivity of the PHA-response was not significantly changed after treatment suggesting that the immunosuppression observed after irradiation is partly due to an increased production of PGs rather than an increased PG-sensitivity of lymphocytes.