Characteristics of peripheral blood NK and NKT-like cells in euthyroid and subclinical hypothyroid women with thyroid autoimmunity experiencing reproductive failure.

Thyroid autoimmunity (TAI) appears to play a crucial role in female infertility, recurrent pregnancy loss and IVF failure. Thyroid autoantibodies against thyroid peroxidase and thyroglobulin have been shown to represent an independent risk factor for infertility and miscarriage. Moreover, thyroxin hormone administration reduces the risk of obstetrical complications in TAI positive women. The aim of our present study was to investigate the immunological background of female infertility and recurrent pregnancy loss in euthyroid and subclinical hypothyroid women with TAI focusing on innate immunity. Phenotypic and functional analysis was carried out on peripheral blood mononuclear cells from healthy donors and TAI patients by flow cytometry. Our findings show Th1 oriented changes of innate immunity in the peripheral blood of women suffering from thyroid autoimmunity. Elevated NK and NKT-like cells ratios and enhanced natural cytotoxicity of TAI positive women reveal an altered immune status with possible negative impact on pregnancy outcome. It is important to notice that immune alterations are already established in the euthyroid phase of autoimmune thyroiditis before endocrine dysfunction develops and only the presence of thyroid autoantibodies indicate TAI condition. For this reason, screening of healthy women of reproductive age for the presence of thyroid autoantibodies would be beneficial not only from the endocrinological aspect but from the reproductive point of view since, although yet unexplained, thyroid hormone administration may improve pregnancy outcome.