Thyrocyte specific killer cell activity is decreased in patients with thyroid carcinoma

Natural killer cells (NK) are important in immune surveillance, and they have found to be decreased in the serum of patients with various types of malignancies. In patients with thyroid carcinoma, we investigated NK activity of peripheral lymphocytes directed against either a standard tumor cell target, K562, or against the clinically relevant target cell, the thyrocyte. Although NK-cell activity was normal when directed against K562 cell targets, NK-cell activity was reduced when labeled thyrocytes were used as target cells. At effector to target cell ratios of 100:1 and 20:1, there was 43 +/- 3% (n = 7) and 29 +/- 3% (n = 7) lyses of thyrocytes using normal lymphocytes, and 17 +/- 4% (n = 5) and 13 +/- 2% (n = 3) using lymphocytes from patients with thyroid carcinoma. These findings suggest that NK-cells have distinct subpopulations and that immune surveillance against specific thyrocyte target cells may be important in thyroid cancer.