Introduction
Infertility is defined as the failure to conceive after one year of unprotected intercourse. Approximately 7%–15% of couples of reproductive age suffer from infertility. Many factors, including endocrine and immunological factors, might predispose a couple to infertility [1]. Unexplained infertility (UEI) is a frustrating state for the subfertile couple with unknown causes. UEI is a diagnosis of exclusion when the necessary infertility workup is found to be normal [2]. Involvement of the immune system in unexplained infertility has been found [1].
It is known that the induction of immunologic tolerance in the decidua is vital to accept fetal alloantigens. Cytokines play an important role in establishing and maintenance of such tolerance. Th1 cytokines (like IFN-γ, IL-2, and TNF) cause pregnancy failure, whereas Th2 cytokines (like IL-4, IL-5 and IL-10, which suppress Th1 responses) cause the tolerance to the fetus and pregnancy. Imbalance of the cytokine network can lead to impaired pregnancy and infertility, including unexplained infertility [3].
Published studies highlighted that reduced fertility might be associated with the dysregulation of immune system reactions resulting in autoimmunity [4, 5]. One of the most common autoimmune diseases that affect females in the reproductive age is Hashimoto thyroiditis [6].
Hashimoto’s thyroiditis (HT) is an autoimmune thyroid disease characterized by follicular lymphocytic infiltration in the thyroid gland with the formation of germinal centres, atrophy of the follicular epithelial cells, Hurthle cell change, and gradual fibrous replacement of the thyroid parenchyma [7]. Disturbed balance of pro- and anti-inflammatory cytokines are thought to play an essential role in the pathogenesis of autoimmune thyroid diseases. Correlation between a high level of Interferon (IFN)- γ and autoimmune thyroiditis has been widely established [8].
Therefore, we aimed to evaluate serum IFN- γ level and the level of expression of IFN- γ gene in Egyptian women with HT and their possible associations with UEI. Accordingly, we can use IFN- γ level and the level of expression of IFN- γ gene as an Immunological marker for UEI in female patients suffering from HT.