Radioiodine-induced changes in lymphocyte subsets in patients with differentiated thyroid carcinoma

Abstract

This study evaluated changes in lymphocyte subsets in patients with thyroid carcinoma who received iodine-131 for diagnostic and therapeutic purposes. Twenty thyroid cancer patients were entered in the study after total thyroidectomy: ten patients (group A) underwent whole-body scintigraphy with 185 MBq of (131)I and the other ten (group B) received 3700 MBq of (131)I therapy. All patients were in a hypothyroid state at the time of administration of (131)I and started L-thyroxine 150 microg/day 3 days after (131)I administration. Free and bound triiodothyronine and thyroxine, thyroid-stimulating hormone, thyroglobulin, thyroglobulin antibodies, thyroid peroxidase/microsomal antibodies, white blood cell, lymphocyte counts and lymphocyte subsets were serially determined at baseline and at days 2, 7, 15, 30 and 60 after (131)I administration. Twenty healthy age- and sex-matched individuals were used as a reference population for lymphocyte subset values. In group A only a reduction in NK cells at days 7 (P=0.043) and 15 (P=0.037) was observed. In group B, patients showed a delayed reduction in the total lymphocyte count at days 15, 30 and 60 (P=0.008, 0.004 and 0. 018, respectively), and a decrease in B cells throughout the study (at days 7, 15, 30 and 60: P=0.006, 0.0017, 0.0017 and 0.0017 respectively). A transient decrease in NK cells was observed at days 15 (P=0.025) and 30 (P=0.008). Among T cells, the helper phenotype (CD4+) was mainly affected, resulting in a reduction in the CD4+/CD8+ ratio at day 60 (P=0.046). Comparing the two groups, the numbers of B lymphocytes at day 30 (P=0.023) and NK cells at days 2 (P=0.037) and 30 (P=0.023) were significantly lower in group B. Neither group showed any clinical sign of immunosuppression during the follow-up period. In patients with thyroid cancer the sensitivity of lymphocytes to the effects of (131)I administered for diagnostic or therapeutic purposes depends upon lymphocyte phenotype and (131)I activity. NK cells are the most radiosensitive cells, being reduced even by low (131)I activity. At higher activity all subtypes show a reduction, which is more marked and prolonged for B lymphocytes and, to a lesser extent, for T-helper lymphocytes. These changes do not result in clinically relevant immunosuppression.

The effects of thyroid hormones on circulating markers of cell-mediated immune response, as studied in patients with differentiated thyroid carcinoma before and during thyroxine withdrawal

“…In our study, the percentage of CD4 þ T lymphocytes in peripheral blood was diminished in patients when on TSH-suppressive thyroxine treatment. This finding might be related to previous treatment with 131 I, which might influence lymphoid populations, yet diagnostic or therapeutic doses of 131 I do not usually result in clinically relevant immuno-suppression (38). However, a transient decrease in NK cells, B and CD4 þ T lymphocyte counts, occurring up to 15, 30 and 60 days respectively, has been reported after therapeutic doses of 131 I in patients with differentiated thyroid carcinoma (38).…”

The changes in complete blood count in thyroid cancer patients treated with radioactive iodine ablation therapy

“…Natural killer cells are most sensitive, followed by B lymphocytes and T-helper lymphocytes. However, these do not result clinically in an immunosuppression [8,9]. Severe and permanent bone marrow suppression was reported by Benua et al [10] in 8 of 59 patients treated with RAI.…”

Blood lymphocyte blastogenesis in patients with thyroid dysfunction: ex vivo response to mitogen activation and cyclosporin A

“…Malignant disease in the history of the enrolled subjects may have caused alterations in lymphocyte activation [12] or lymphocyte subsets, as shown in ovarian carcinoma cells that were able to exhibit suppressive ability in activated naive T cells by producing multiple cytokines [13]. Moreover, previous treatment with I 131 might have transiently influenced lymphoid populations, yet diagnostic or therapeutic doses of I 131 do not usually result in clinically relevant immunosuppression [14].…”