Experimental autoimmune encephalomyelitis (EAE) had been believed to be a Th1-mediated disease. Unexpectedly, IFN-γ did not worsen the EAE and antibody to IFN-γ could not protect it but made EAE worse.[39] In contrast, IL-17-producing T cells caused EAE in adaptive transfer experiment.[40] The discovery of IL-17 secreting CD4+ T (Th17) cells was a major step toward resolving a puzzle of EAE. In humans, Th17 cells LDE225 are known to develop from naïve CD4+ T cells by TGF-β, IL-6, IL-23, and IL-1 and secrete IL-17A, IL-17F, IL-22, and IL-26.[14, 41-43] The transcriptional factor to develop Th17 cells is retinoic acid-related orphan receptor γt (RORγt) in humans and mice.[14] Early Th17

cell studies were focused in autoimmune diseases such as EAE, rheumatoid arthritis, asthma, inflammatory bowel diseases, and lupus.[44, 45] Thereafter, studies of Th17 cells have been expanded to allograft rejection, host defense, metabolic disorders, and tumor immunology.[44, 46, 47] IL-17 is known to induce inflammation via neutrophil

infiltration and stimulation of IL-1, IL-6, IL-8, TNF-α, nitric oxide, matrix metalloproteinase, receptor activator for nuclear factor κB ligand (RANKL) and granulocyte-macrophage colony stimulating factor (GM-CSF) production.[48, 49] Major source of IL-17 production is CD4+ T cells, but other immune cells including CD8+ cells, γδ T cells, CD14+ monocytes, lymphoid tissue inducer (LTi) cells, and NK-like cells also secrete IL-17.[50, 51] These IL-17-producing cells are believed AT9283 concentration to play a role in defense against viruses, some bacteria, fungi, and chronic inflammation. There is little information regarding the expression of peripheral blood and uterine regulatory T cells during a menstrual cycle. Arruvito et al.[52] have reported that the proportion of peripheral blood Foxp3+ T cells was significantly increased in the late follicular phase as compared to that in the luteal phase (Table 1). They also presented a positive correlation between the level of regulatory T cells and the serum estradiol concentration. This finding may indicate that estradiol positively affects the expansion of regulatory

T cells. However, other studies did not find any significant association between the estradiol level and the Protein kinase N1 percentage of CD4+ CD25high T cells during a menstrual cycle.[53] There is an indirect regulatory T-cell study carried out in the human endometrium. The density of endometrial Foxp3+ regulatory T cells rose gradually throughout the proliferative phase.[54] The authors suggested that the increase in peripheral blood and endometrial Foxp3+ regulatory T cells may play a role in the implantation of an embryo in the mid-secretory phase. PB: ? EM: in the mid-secretory phase PB: in number and function Decidua: PB: Decidua: PB: Decidua: ? For regulatory T-cell recruitment into the endometrium and deciduas, some chemokine receptors and their ligands are likely involved.