Ortega-Rodríguez AC, Martínez-Hernández R, Monsiváis-Urenda A, et al. - In this cases and controls, observational study, researchers analyzed the levels and function of PD-1 ⁺ NK cells in samples from autoimmune thyroid disease (AITD) patients. This investigation was carried out at hospital Universitario la Princesa, Spain. The sample consisted of 40 patients with AITD, 16 with Hashimoto thyroiditis (HT) and 24 with Graves’ disease (GD), and 15 healthy controls. Increased levels of NK cells and the CD56 ^dimPD-1 ⁺ subset have been identified in patients with GD. In HT, an enhanced expression of the regulatory receptors NKG2A and NKG2C by CD56 ^brightPD-1 ⁺ NK cells has been discovered. The complex role of these cells in this pathogenesis is further supported by the different abnormalities in NK cell subset levels, the expression of PD-1 and its function in AITD patients.