Vitamin D has a pivotal role in regulating immune responses by promoting Th2 immune responses and suppressing Th1 responses. Propensities to a Th1 immune response and increased NK-cell levels and cytotoxicity have been reported in women with recurrent pregnancy losses (RPL). In women with RPL, vitamin D deficiency is prevalent
IntroductionVitamin D is a group of secosteroids and has a major role in maintaining skeletal health. Various effects of vitamin D on extra skeletal tissues have been reported as well, during the past decade [1]. Vitamin D deficiency is endemic for both men and women and across different age groups in the US population [2]. Low C 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.eji-journal.eu Eur. J. Immunol. 2015. 45: 3188-3199
Clinical immunology
3189vitamin D level has been linked to major common health problems in populations, particularly inflammatory conditions such as cardiovascular disease, cancers, diabetes, autoimmune diseases including multiple sclerosis, rheumatoid arthritis, and others [3]. In addition, vitamin D deficiency is a predisposing factor for various female diseases such as osteoporosis, uterine fibroids, endometriosis, and breast cancer and a risk factor for obstetrical complications such as gestational diabetes and preeclampsia [4,5]. Recently, we have reported that 47.4% of women with recurrent pregnancy losses (RPL) have vitamin D deficiency [6]. In women with RPL, decreased vitamin D level was associated with the increased prevalence of antiphospholipid antibody, antinuclear antigen antibody, anti-ssDNA, and anti-thyroperoxidase antibody. In addition, peripheral blood CD19 + B and CD56 + NK-cell levels and NK cytotoxicity were significantly higher in women with low vitamin D level when compared with those of normal vitamin D level [6]. Normal pregnancy is associated with Th2 shift in T-cell immunity [7]. The comparable shift in NK-cell immunity has been reported during normal pregnancy including a bias to NKr1 that produce IL-10 in peripheral blood, and NK3 cells that produce TGF-β in decidual NK cells [8]. Additionally, decidual innate lymphoid cell 3 (ILC3) may play a role in innate defenses, and vessel and tissue rebuilding, thus contributing to maintenance of pregnancy [9]. Contrarily, a propensity to Th1 immune response and increased NK-cell levels and cytotoxicity have been reported in women with RPL and multiple implantation failures (MIF) after in vitro fertilization and embryo transfer cycles [10]. Women with miscarriages and preeclampsia as well, have NK1 and NKT1 shift that produce high amounts of IFN-γ and little IL-4 in peripheral blood [11]. Therefore, cellular immune-regulation including innate immunity is critical for human reproduction.Women with RPL and MIF have significantly higher NK-cell levels and cytotoxicity, and dysregulated cytokine production patterns as compared to normal controls [10,12]. Activating receptor expression on NK cells was significantly increased, while inhibitory receptor expression was significantly decreased in ...