Natural killer cells constitute 50–90% of lymphocytes in human uterine decidua in early pregnancy. Here, CD56bright uterine decidual NK (dNK) cells were compared with the CD56bright and CD56dim peripheral NK cell subsets by microarray analysis, with verification of results by flow cytometry and RT-PCR. Among the ∼10,000 genes studied, 278 genes showed at least a threefold change with P ≤ 0.001 when comparing the dNK and peripheral NK cell subsets, most displaying increased expression in dNK cells. The largest number of these encoded surface proteins, including the unusual lectinlike receptors NKG2E and Ly-49L, several killer cell Ig-like receptors, the integrin subunits αD, αX, β1, and β5, and multiple tetraspanins (CD9, CD151, CD53, CD63, and TSPAN-5). Additionally, two secreted proteins, galectin-1 and progestagen-associated protein 14, known to have immunomodulatory functions, were selectively expressed in dNK cells.

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In early pregnancy invading fetal trophoblasts encounter abundant maternal decidual natural killer cells (dNK). dNK express perforin, granzymes A and B and the activating receptors NKp30, NKp44, NKp46, NKG2D, and 2B4 as well as LFA-1. Even though they are granular and express the essential molecules required for lysis, fresh dNK displayed very reduced lytic activity on classical MHC I negative targets K562 and 721.221, Ϸ15% of that of peripheral NK cells. dNK formed conjugates and activating immune synapses with 721.221 and K562 cells in which CD2, LFA-1 and actin were polarized toward the contact site. However, in contrast to peripheral NK cells, they failed to polarize their microtubule organizing centers and perforin-containing granules to the synapse, accounting for their lack of cytotoxicity.lymphocytes ͉ microtubule organizing center ͉ perforin ͉ pregnancy ͉ uterus

Invading human leukocyte antigen-G+ (HLA-G+) extravillous trophoblasts (EVT) are rare cells that are believed to play a key role in the prevention of a maternal immune attack on foreign fetal tissues. Here highly purified HLA-G+ EVT and HLA-G− villous trophoblasts (VT) were isolated. Culture on fibronectin that EVT encounter on invading the uterus increased HLA-G, EGF-Receptor-2, and LIFReceptor expression on EVT, presumably representing a further differentiation state. Microarray and functional gene set enrichment analysis revealed a striking immune-activating potential for EVT that was absent in VT. Cocultures of HLA-G+ EVT with sample matched decidual natural killer cells (dNK), macrophages, and CD4+ and CD8+ T cells were established. Interaction of EVT with CD4+ T cells resulted in increased numbers of CD4+CD25 HI FOXP3+CD45RA+ resting regulatory T cells (Treg) and increased the expression level of the Treg-specific transcription factor FOXP3 in these cells. However, EVT did not enhance cytokine secretion in dNK, whereas stimulation of dNK with mitogens or classical natural killer targets confirmed the distinct cytokine secretion profiles of dNK and peripheral blood NK cells (pNK). EVT are specialized cells involved in maternal-fetal tolerance, the properties of which are not imitated by HLA-G-expressing surrogate cell lines.Treg | FOXP3 | NK cell | human | pregnancy

Invariant CD1d-restricted natural killer T (iNKT) cells comprise a small, but significant, immunoregulatory T cell subset. Here, the presence of these cells and their CD1d ligand at the human maternal-fetal interface was investigated. Immunohistochemical staining of human decidua revealed the expression of CD1d on both villous and extravillous trophoblasts, the fetal cells that invade the maternal decidua. Decidual iNKT cells comprised 0.48% of the decidual CD3؉ T cell population, a frequency 10 times greater than that seen in peripheral blood. Interestingly, decidual CD4؉ iNKT cells exhibited a striking Th1-like bias (IFN-␥ production), whereas peripheral blood CD4؉ iNKT clones exhibited a Th2-like bias (IL-4 production). Moreover, compared to their peripheral blood counterparts, decidual iNKT clones were strongly polarized toward granulocyte͞macrophage colony-stimulating factor production. The demonstration of CD1d expression on fetal trophoblasts together with the differential pattern of cytokine expression by decidual iNKT cells suggests that maternal iNKT cell interactions with CD1d expressed on invading fetal cells may play an immunoregulatory role at the maternal-fetal interface.

Human peripheral blood NK cells may be divided into two main subsets: CD56 bright CD16À and CD56 dim CD16 1. Since TGF-b is known to influence the development of many leukocyte lineages, its effects on NK cell differentiation either from human CD34

HLA-G is the putative natural killer (NK) cell inhibitory ligand expressed on the extravillous cytotrophoblast of the human placenta. Killing of the class I negative human B cell line 721.221 by NK cells is inhibited by the expression of HLA-G. This inhibition is dependent on a high level of HLA-G expression. In the present study, the nature of the receptors that mediate the inhibition has been studied with 140 NK cell lines from two donors and 246 NK clones from 5 donors by blocking the inhibition using monoclonal antibodies against the known NK inhibitory receptors: CD158a, CD158b, and CD94. Both CD94 and the two CD158 proteins can function as receptors, although the former clearly predominates. In many cases, a combination of antibodies to these receptors is required to achieve maximal reversal of inhibition. Moreover, in at least one-third of the NK cells that are inhibited by HLA-G, these antibodies alone or in combination do not reverse inhibition, strongly suggesting the existence of a third major unidentified receptor for HLA-G.

Chorioamnionitis is a major cause of prematurity as well as perinatal morbidity and mortality. The present study observed a marked increase in immunohistochemical staining for Colony Stimulating Factor 2 (CSF2; also known as granulocyte macrophage-colony stimulating factor), a potent neutrophil and macrophage chemoattractant and activator, in the decidua of patients with CAM compared with controls (n = 8; P = .001). To examine the regulation of this CSF2, cultured decidual cells primed with estradiol (E 2 ) or E 2 plus medroxyprogesterone acetate, were exposed to tumor necrosis factor-α or interleukin-1β and secreted CSF2 measured by ELISA. Levels of CSF2 in E 2 plus MPA-treated cultures increased 18-and 245-fold following treatment with TNF or IL1B (n = 7, P < .05). Quantitative RT-PCR demonstrated parallel changes in mRNA levels. This study reveals that CSF2 is strongly expressed in decidua from patients with CAM and indicates TNF or IL1B as important regulators of CAM-related decidual leukocyte infiltration and activation.