E. G. Orlova

Role of Leptin and Ghrelin in Induction of Differentiation of IL-17-Producing and T-Regulatory Cells

We studied isolated and combined effects of leptin and ghrelin on the formation of ILproducing and T-regulatory cells. Leptin in concentrations comparable with its normal blood concentration during pregnancy (trimester II-III) promotes differentiation of peripheral blood CD4+ cells to IL-17-producing cells and enhances IL-17A production, but suppresses the formation of T-regulatory cells in vitro. In contrast, ghrelin in a concentration typical of trimester I-II of pregnancy reduces the number of IL-17-producing cells, but stimulated the formation of T-regulatory cells. The effects of leptin and ghrelin in combination typical of trimester I-II of pregnancy stimulated the formation of T-regulatory cells, while in combination typical of trimester II-III did not shift the balance of T-regulatory cells and IL-17-producing cells, but stimulated the formation of IL-17A. We conclude that leptin and ghrelin play an important role in the maintenance of the balance of IL-17-producing and T-regulatory cells during pregnancy.

Leptin and ghrelin regulate dendritic cell maturation and dendritic cell induction of regulatory T-cells.

171 The peptide hormones leptin and ghrelin are func tional antagonists in the energy and fat metabolisms and have multidirectional immunoregulatory activity [1]. These hormones are important for the gestation processes, control of the implantation, and growth and development of the embryo [1]. During the preg nancy, significant changes in fat and energy metabo lisms occur, and dramatic disturbances of fat metabo lism are associated with severe defects of the reproduc tive function [1]. The prerequisite for safe motherhood is the formation of the tolerance of the mother’s immune system to fetal antigens [2] caused by the changes in the balance of regulatory subpopulations of T cells, namely, a decrease in the number of IL 17 producing T helpers (Th17) and an increase in the number of T regulatory lymphocytes (Treg) in the peripheral blood. These changes are caused by an increase in the proportion of tolerogenic (immature) dendritic cells (DCs) [3]. DCs are the main antigen presenting cells which produce a wide range of cytok ines, depending on the maturation stage and the acti vation conditions; they also determine the differentia tion of naive CD4+ T cells and the type of adaptive immune response [4]. Immature DCs produce tolero genic cytokines, such as interleukin (IL) 10 and trans forming growth factor β1 (TGF β1), thus activating the formation of adaptive (a) Treg and induce immune tolerance [4]. The hormones and cytokines such as IL 10 and TGF β1 can stabilize the tolerogenic capacity of immature DCs [2–4]. Thus, the study of the factors affecting the DC maturation and CD4+ T cell differentiation is important for the understanding of the mechanisms controlling the immune response direction and the formation of the peripheral toler ance during pregnancy.

Adrenergic regulation of phagocytic activity of peripheral blood neutrophils, monocytes, and eosinophils in stressed rats.

Time course of phagocytic activity of peripheral blood neutrophils, monocytes, and eosinophils was studied in rats exposed to acute stress under conditions of propranolol blockade of β-adrenoceptors. The important role of β-adrenergic mechanisms in the regulation of phagocytic functions in stress was demonstrated.

The role of pregnancy-associated hormones in regulation of expression of molecules responsible for NK cell functional activity

261 The phenomenon of tolerance of the immune syss tem of the mother to the genetically alien fetus is an urgent problem of reproductive immunology, in the framework of which analysis of the role of hormones in the immunity regulation is the most important line of research. It is known that, in the period of early pregg nancy, natural killers (NK cells) are the dominant population among lymphoid cells localized in the decidual membrane [1]. NK cells with the CD16 + CD56 dim phenotype account for over 90% of peripheral NK cells and exhibit high cytoxicity comm pared to CD16 – CD56 bright [2]. It is suggested that decidd ual NK cells mature from peripheral CD16 – CD56 bright lymphocytes migrating to the uterus [3]. During pregnancy, the cytotoxic potential of the NKKcell population decreases due to a decrease in the percentage of CD16 + CD56 dim lymphocytes. At the same time, the increased concentration of CD16 + 56 dim NK cells in the peripheral blood of women is associated with habitual miscarriage of pregg nancy [4], which is related to their ability to lyse cells of trophoblast [2]. In turn, CD16 – CD56 bright NK cells express inhibitory receptors, such as NKG2A and LILRB, due to which they fulfill an immunotrophic function instead of the cytolytic one [2]. For instance, CD16 – CD56 bright cells directly participate in implann tation, neoangiogenesis, and support of pregnancy [3]. In addition, NK cells potentiate the induction of TT regulatory lymphocytes, which leads to formation of immunologic tolerance in the period of pregnancy [5]. Along with CD16 molecule, the activation recepp tors NKG2D and NKp46 are responsible for the cytoo toxic function of NK cells, the latter is constitutionally expressed over the entire population of NK cells and serves as the main marker for their identification [6]. It is known that hormones can determine the funcc tional activity of the immune system cells [7]. The most physiologically important, from this point of view, are hormones that appear in the woman body only during pregnancy—chorionic gonadotropin (CG) and estriol (Е 3). Apart from this, the immunoo regulation function is exercised by hormones whose level considerably increases during pregnancy due to placental synthesis. These are, first of all, leptin, ghree lin, and kisspeptin. Their important role in reproducc tion regulation is well known [8–10]; however, the modulating activity with respect to NK cells at conn …

Hormonal regulation of thymic-stage differentiation of IL-17-producing and T-regulatory lymphocytes.

65 The immune system is exposed to a significant influence of the endocrine system. The thymic stage of T lymphocyte differentiation, when the main T cell populations are formed, is a potential target of the hormonal regulatory effect. Natural T regulatory lymphocytes (nTreg) that inhibit the effector cell pro liferation and IL 17 producing T lymphocytes (Th17) involved in initiating the inflammatory and autoim mune responses are the most important among T cell populations [1]. The immune response direction and formation of immune tolerance (during pregnancy or tumor growth) depend on the balance of regulatory T lymphocyte subtypes (Th17/Treg) [1].

Hormonal regulation of the thymic stage of differentiation of invariant NKT cells.

331 Natural killer T cells (NKT cells) are effectors of innate immunity characterized by cytotoxic and immunoregulatory activities [1]. NKT cell differentii ation occurs in the thymus from doubleepositive (СD4 + СD8 +) thymocytes [1]. In humans, the NKT cell population is mainly presented by invariant (i) NKT cells expressing TTcellular receptor (TCR) with only one variant of the VVdomain of the αchain (Vα244JαQ) complexed with Vβ11, in contrast to nonninvariant lymphocytes (minor subpopulation) [1]. The TCR of iNKT cells has the ability to distinguish glycolipids presented by CD1d similar to the molee cules of the major histocompatibility complex [1]. The quantity of iNKTTcells in peripheral blood was shown to decrease in the case of normal pregnancy, while an increase in their quantity was reported to be associated with spontaneous miscarriage and preeclampsia [2]. Despite the small amount of iNKT cells in the periphh eral blood (less than 1.2% of the total quantity of T cells), they possess the ability for the rapid and massive cytokines production, which determines their role in the regulation of immune reactions [1]. Previously, we demonstrated that reproduction hormones, such as chorionic gonadotropin (hGC) and estriol (E 3), as well as leptin and ghrelin produced by placenta, were involved in the regulation of express sion of NKT cell surface markers in the peripheral blood [3] and were characterized by their own differr entiating and growth effects on intact thymocytes. Leptin is known to prevent steroiddinduced thymocyte apoptosis through stimulating СD4 + СD8 + thymocyte proliferation [4], while ghrelin is involved in prevenn tion of ageerelated thymus involution [5]. Accordd ingly, the problem of hormonal regulation of the thyy mic stage of iNKT cell differentiation is urgent in the context of fetomaternal immune interactions. The aim of the present study was to investigate the ability of hCG, Е 3 , leptin and ghrelin to regulate the growth and differentiation of iNKT cells at the level of intrathymic TTcell precursors. It has been established that hCG, Е 3 , and ghrelin decrease the quantity of iNKT cells in the cultured 72h lymphocytes at concentrations similar to the levv els of these hormones during pregnancy trimesters II and III. In contrast, leptin was observed to increase significantly the number of iNKT cells at a concentration similar to its level during pregnancy trimesters II and III. All the hormones studied did not significantly affected the quantity of iNKT cells …

Leptin as an Immunocorrecting Agent during Normal Pregnancy

Experiments were performed with leptin in doses observed during pregnancy. We studied the effect of leptin on expression of membrane molecules and cytokine production by peripheral blood mononuclear cells from women. Leptin increased the expression of HLA-DR on T lymphocytes, stimulated the production of TNF-α and IL-6, and did not affect secretion of IL-2, IL-4, and IL-10 by mononuclear leukocytes. Leptin in a dose comparable to that during the 1st trimester of pregnancy increased the percentage of NK cells with membrane CD16 and CD56, stimulated the production of IFN-α by mononuclear leukocytes, and did not modulate the number of CD16+56+NKT cells. Treatment with leptin in a dose for the second-third trimesters of pregnancy was followed by a decrease in the percentage of CD16+56+NKT cells and increase in the number of NKT cells expressing CD16 and CD56. Our results indicate that leptin play an important role in the regulation of membrane molecule expression and cytokine production by mononuclear leukocytes.

The influence of chorionic gonadotropin and estriol on NK cell phenotype and functional activity

The influence of chorionic gonadotropin (CG) and estriol (Е3) at the concentrations typical of pregnancy on the expression of phenotypic markers and cytokine production by separated NK cells has been studied. It has been found that these hormones increase the percentage of CD56bright L-selectin+ NK cells, but also stimulate the expression of the inhibitory molecule NKG2A in the lymphocytes. In addition, Е3 and CG stimulate the production of TGF-β, inhibiting the secretion of all other cytokines by separated NK cells. In general, these hormones contribute to the formation of the phenotype and cytokine spectrum characteristic of the regulatory NK3 subpopulation of NK cells during pregnancy.

Roles of leptin and ghrelin in the regulation of the phenotype and cytokine production by NK cells from peripheral blood

Both leptin and ghrelin used separately at the concentrations corresponding to trimesters II–III of pregnancy increase the number of CD56bright NK cells in mononuclear cell suspension; their combination also enhances the L-selectin expression on the surface of these cells in the culture. These hormones do not affect the production of TGF-β1, IL-17А, or IFN-γ by NK cells, and they inhibit the production of IL-10. Leptin decreses the IL-4 production by NKp46+ cells, but the presence of ghrelin abrogates this effect.

The effect of kisspeptin on the functional characteristics of isolated NK cells

The effect of kisspeptin at concentrations typical of pregnancy on the functional activity of isolated cytokine-primed NK cells has been investigated. The hormone has been shown to promote an increase in the proportion of CD56bright NK cells, as well as an increase in the L-selectin expression on the cell surface. Assessment of cytokine levels has shown that kisspeptin suppresses the production of IL-4, IL-10, and IFN-γ while stimulating the production of TGF-β by isolated NK cells. The overall effect of the hormone investigated consisted in the formation of a phenotype and a cytokine spectrum characteristic of the regulatory NK3 subpopulation of NK cells in pregnancy.