Natural cytotoxicity of peripheral blood leukocytes from normal subjects and patients with Hashimoto's thyroiditis against human adult and fetal thyroid cells.

Natural cytotoxicity of human peripheral blood leukocytes against fetal and adult human thyroid cells was investigated in vitro. Natural killer (NK) cell activity was determined at various effector: target cell ratios in a standard 51Cr release assay with human thyroid cells as targets. The effector cells were unfractionated peripheral blood mononuclear cells obtained by Hypaque-Ficoll gradient centrifugation. We have demonstrated that peripheral blood leukocytes from normal subjects and patients with Hashimoto's thyroiditis exhibit natural cytotoxicity against both human fetal and adult thyroid cells. This was effector: target cell ratio and incubation time dependent. Although there was a tendency for increased killing of fetal thyroid cells by peripheral blood leukocytes from patients with Hashimoto's thyroiditis compared to age/sex matched normal subjects this was not significant and there were no significant differences between the two groups for killing of adult thyroid cells. A possible role for natural cytotoxicity in progressive thyroid tissue destruction in Hashimoto's thyroiditis is discussed.