Changes of the blood lymphocyte population following 131I treatment for nodular goiter

The blood lymphocyte population was examined in 34 patients who were treated with 131I for toxic or atoxic nodular goiter. The patients received one to three doses of 300-550 MBq of 131I administered at 1 week intervals. Lymphocyte counts were significantly reduced both 1 and 6 weeks after treatment. This reduction was accompanied by a changed composition of the lymphocyte population. The frequency of lymphocytes expressing membrane receptors for C'3 (EAC-rosette forming) was significantly reduced 1 and 6 weeks after 131I-administration. At 6 weeks there was a slight but statistically significant increase of the frequency of T-cells as identified by Leu 1 monoclonal antibodies. This was largely caused by an increased proportion of helper/induced T-cells as identified by Leu 3a monoclonals. 131I-treatment also reduced the capacity of lymphocytes to secrete immunoglobulins (Ig) upon PWM-stimulation. The most pronounced effect was observed for IgM. Secretion of IgG and IgA were less reduced. Mitogenic stimulations of lymphocytes with PHA and ConA were not significantly changed. We conclude that these changes observed, with the exception of mitogen reactivity, are essentially similar to those occurring after external radiation therapy for cancer. We speculate that blood lymphocytes passing through the continuously irradiated gland are damaged mainly by emitted beta-particles.