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J S Hunt

Publications and source records attributed to J S Hunt.

160 records · Page 9Linked to original sources
PubMedDate not supplied

Ultrastructure of cultured rat placental cells.

Rat placental cells (RPCs) derived from explants of gestation day 12 chorioallantoic placental primordia were propagated as ascites RPCs and as in vitro cultured RPCs. Although the morphological characteristics of ascites RPCs and in vitro cultured RPCs differed markedly by light microscopy, evaluation by electron microscopy revealed that all RPCs were epithelioid. Morphological differences at the light microscope level were attributable to environmental conditions. When RPCs were compared with placental cells in situ, RPC characteristics most closely resembled those of layer-one trophoblast cells (germinal cytotrophoblast) present in the labyrinthine region of the placenta. RPCs, which appear to be a relatively homogeneous population of trophoblast cells, may be valuable tools for evaluating the relationships between maternal and fetal cells during pregnancy and for studying the growth and differentiation of extraembryonic cells.

Animals↗
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Expression of histocompatibility antigens, transferrin receptors, intermediate filaments, and alkaline phosphatase by in vitro cultured rat placental cells and rat placental cells in situ.

Rat placental cells (RPCs) derived from the chorioallantoic placenta of day-12 Holtzman rats were tested for the expression of class I and class II RT I histocompatibility antigens, transferrin receptors, intermediate filaments, and alkaline phosphatase. The binding of mouse monoclonal antibodies to those antigens by RPCs was compared with the binding of the same reagents to rat placental cells in situ. RPCs expressed low levels of class I antigens and failed to express detectable levels of class II antigens. RPCs resisted up-regulation of expression of class I antigens by interferon-gamma, and did not express class II antigens following exposure to medium containing interferon. Transferrin receptors; cytokeratin intermediate filaments, and alkaline phosphatase were universally expressed by RPCs. Taken together with the patterns of expression of the same antigens by rat placental cells in situ, the results suggest that RPCs comprise labyrinthine trophoblast cells. Those cells may provide a valuable new approach for studying the structures and functions of trophoblast cells in vitro.

Alkaline Phosphatase↗
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Mouse and rat placental cell lines express abundant amounts of laminin.

Placental cell lines derived from midgestation placentae of outbred mice and rats were evaluated for the expression of the extracellular matrix protein laminin. The murine cell line, which has not been previously reported, demonstrates morphological characteristics similar to those of the rat cell line. Placental cell lines grow vigorously both in vitro and when transplanted to the peritoneum of allogeneic hosts. When transplanted, placental cells form cyst-like structures (with acellular cores) suspended in the peritoneal fluid, and invade abdominal structures forming solid masses. Using immunohistology, laminin was identified within in vitro cultured cells, within cyst-like structures and their acellular cores, and as a major component of the extracellular matrix of solid masses. Laminin was also identified in the normal rat chorioallantoic placenta. Evaluation of extracts from in vitro cultured placental cells, transplanted placental cells, and the normal chorioallantoic placenta by electrophoresis and immunoblotting demonstrated that laminins were composed of two species with molecular weights of 400,000 (A-chain) and 200,000 (B-chains). Mouse and rat placental cell lines may be valuable for studying laminin biosynthesis and function in the developing placenta.

Animals↗
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Isolation of phenotypically distinct trophoblast cell lines from normal rat chorioallantoic placentas.

Growth characteristics and the expression of trophoblast-associated markers by six cell lines generated from midgestation chorioallantoic placentas of outbred (Holtzman) and inbred (Lewis, PVG.RT Ir8) rats were evaluated. The cells comprising all cell lines were epithelioid (contained cytokeratin-type intermediate filaments), had normal (2n, 4n) DNA content, and synthesized the extracellular matrix glycoprotein laminin. Variability was observed among the lines in all other characteristics: median cell size, rate of growth, serum dependency, responses to transferrin and dibutyryl cyclic adenosine-3',5'-monophosphate, synthesis of some major proteins, alkaline phosphatase activity, and the expression of immunoreactive placental lactogen-II. In general, cell lines with smaller mean cell sizes grew rapidly and required little serum for maintenance in vitro; cell lines with larger mean sizes grew more slowly and preferred higher concentrations of serum. Some associations between mean cell size/rate of growth and other characteristics were observed. No major differences were apparent between cell lines generated from outbred and inbred rat placentas. Trophoblast cell lines expressing distinct phenotypes provide a valuable new approach for studying a wide range of trophoblast cell activities.

Allantois↗
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Current topic: the role of macrophages in the uterine response to pregnancy.

Immunohistological experiments have established patterns of distribution of macrophages in the pregnant uterus and some data have been accumulated on potential chemoattractants for these cells. The results of several lines of inquiry indicate that, as with macrophages in other tissues, these cells are multi-functional. Further experimentation is likely to be technically demanding because of indications that intricate hormone-prostaglandin-cytokine networks regulate uterine macrophage activities. The question of cytokine synthesis by uterine macrophages is particularly intriguing (Hunt, 1989a, Journal of Reproductive Immunology, 16, 1-17) and particularly difficult. These morphologically heterogenous cells are interspersed throughout the uterus with other types of cells that synthesize some of the same molecules, and the manipulations required for isolation could easily affect transient gene transcription (Taniguchi, 1988). Thus, many experiments must be performed on intact tissues using immunohistology and in situ hybridization. Although these remarkable cells undoubtedly contribute to the required developmental events of pregnancy, uterine macrophages may have detrimental as well as beneficial effects, particularly in cases of infection. Activation by interferons and bacterial lipopolysaccharides (LPS) disrupts normal synthetic patterns, and results in secretion of increased concentrations of bioactive proteins and lipids. Higher levels of IL-1 (Romero et al, 1989), TNF-alpha (Casey et al, 1989) and IL-6 (Romero et al, 1990), as well as increased levels of prostaglandins (Romero et al, 1987), all products of activated macrophages, are associated with pregnancy termination due to infection. Some of these molecules could induce premature labour, and others might alter cellular functions.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Movement↗
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Expression of the interferon-gamma receptor gene in mouse placentas is related to stage of gestation and is restricted to specific subpopulations of trophoblast cells.

In order to evaluate the potential of placental cells to bind the multifunctional cytokine, interferon-gamma (IFN-gamma), tissues collected from pregnant Swiss mice were analysed for IFN-gamma receptor (IFN-gamma R) mRNA and protein. Northern blot hybridization studies indicated that the relative abundance of IFN-gamma R mRNA increased as gestation progressed to term. Analysis by in situ hybridization revealed that trophoblast cells first contained high steady state levels of IFN-gamma R mRNA at g.d. 12. At g.d. 12 and 14, transcription was restricted to cells in the spongiotrophoblast region and nests of similar cells in the labyrinthine region. These cells also contained immunoreactive IFN-gamma R protein. By g.d. 18, IFN-gamma R mRNA was clearly detectable in large spongiotrophoblast cells and labyrinthine trophoblast. IFN-gamma R mRNA was low to absent in giant trophoblast cells at all stages of gestation. Specific mRNA was present in parietal and visceral yolk sac cells by g.d. 14. Thus, expression of the IFN-gamma R gene in mouse placental cells is influenced by stage of gestation, cell lineage and state of differentiation. Whether or not these cells respond vigorously to IFN-gamma with induction of antiviral proteins, increased MHC class I antigens and growth modulation may therefore be determined by their expression of specific receptors for this pluripotent cytokine.

Allantois↗
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HLA-G1 protein expression is not essential for fetal survival.

HLA-G is a nonclassical, class I HLA gene that is primarily expressed by fetal cells at the maternal-fetal interface and is thought to play a key role in the induction of tolerance in pregnancy. This paper reports the identification of a single base pair deletion at position 1597 (1597delC) in exon 3 (encoding the alpha2-domain) of HLA-G on 20 of 272 (7.4 per cent) African American chromosomes, three of 102 (2.9 per cent) Hispanic chromosomes, and none of 134 Caucasian chromosomes. This relatively common frameshift mutation results in amino acid substitutions in all of the residues in the second half of exon 3 including the conserved cysteine at codon 164. An adult individual was identified who was homozygous for this 'null' allele, and a first trimester placenta that was homozygous for 1597delC had no detectable HLA-G1 protein. These data indicate that expression of HLA-G1 protein is not essential for fetal survival.

Adult↗
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Monocyte-mediated erythrocyte destruction. A comparative study of current methods.

Three assay systems-EAIgG rosette formation, 51Cr release, and erythrophagocytosis-were used to quantitate interaction between antibody-coated human erythrocytes and normal blood monocytes. The three methods were compared in terms of time requirements and sensitivity. Erythrophagocytosis required more time to perform (2 hours) than did rosette tests (30 minutes) but less than minimum 51Cr release assays (5.5 hours). Erythrophagocytosis was 20-fold more sensitive than either of the other two procedures. Results obtained with purified IgG anti-D and with antibodies induced by transfusion or pregnancy were similar.

Antibodies, Anti-Idiotypic↗
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Factors influencing monocyte recognition of human erythrocyte autoantibodies in vitro.

Erythrocytes, serum, and blood monocytes from patients with erythrocyte autoantibodies were examined by in vitro serologic and cell culture procedures in order to evaluate factors modulating patient mononuclear phagocyte activity. Monocyte recognition of autoantibody-coated erythrocytes was influenced both by antibody titer score and by the monocyte source. The results suggest that patients with low serum autoantibody titer scores and normal monocyte behavior are less likely to destroy autologous or normal donor erythrocytes than are patients with high-serum antibody titer scores or enhanced monocyte activity. We conclude that patient, rather than normal donor monocytes, must be used in cellular assays designed to predict the fate of erythrocytes transfused into patients with erythrocyte autoantibodies.

ABO Blood-Group System↗
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Trophoblastic cell lines generated from tumour necrosis factor receptor-deficient mice reveal specific functions for the two tumour necrosis factor receptors.

In mice and humans, expression of the tumour necrosis factor receptor-1 (TNF-R1) gene in placental trophoblast cells is constitutive whereas expression of the TNF-R2 gene is developmentally programmed. In order to study the individual functions of TNF-R1 and -R2 in this lineage, cell lines were generated from placental explants of homozygous matings of gestation day 10 outbred mice (Swiss-Webster), TNF-R1-deficient (TNF-R1-/-) and TNF-R2-/- transgenic mice as well as the background strain for the TNF-R2-/- mice (WT, C57BL/6x129). All of the cells exhibited trophoblast markers; they contained cytokeratin intermediate filaments, expressed alkaline phosphatase activity and displayed transferrin receptors, but were negative for vimentin filaments and the macrophage marker, F4/80. Analysis of DNA by polymerase chain reaction demonstrated the expected TNF-R genotype in each line. In experiments testing the effects of recombinant mouse TNF-alpha (rmTNF-alpha) on viability and proliferation of the cell lines, rmTNF-alpha modestly but dose-dependently inhibited the growth of WT and TNF-R2-/- cells while having no effect on TNF-R1-/- cells. Actinomycin D-treated WT and, to a lesser extent, TNF-R2-/- cells, were more sensitive to growth inhibition than untreated cells whereas TNF-R1-/- cell responses remained unchanged. These data indicated that rmTNF-alpha inhibits growth of trophoblastic cells through TNF-R1 and that newly synthesized protein(s) provide partial protection against toxicity. In contrast to the receptor species-specific effects on cell growth exerted by rmTNF-alpha, both TNF-R mediated inhibition of alkaline phosphatase activity. Collectively, the observations support the postulate that receptor expression is the key factor which determines the nature and extent of TNF-alpha effects on trophoblast cell growth and function.

Alkaline Phosphatase↗
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Death-inducing tumour necrosis factor (TNF) superfamily ligands and receptors are transcribed in human placentae, cytotrophoblasts, placental macrophages and placental cell lines.

Human placentae and two of the cell types in placentae (cytotrophoblasts and macrophages) were examined by RT-PCR for transcripts of the eight TNF superfamily ligands known to induce death of activated immune cells, tumour cells, and virus-infected cells (TNFalpha, LT alpha, LT beta, FasL, TRAIL, TWEAK, LIGHT, 4-1BBL). Transcripts for all ligands were detected in term placenta but LT alpha and 4-1BBL were not detected in first trimester placenta. Although term cytotrophoblasts contained mRNAs specific for TNF alpha, LT alpha, TWEAK, and 4-1BBL, messages encoding LT beta, FasL, TRAIL, and LIGHT were absent. In term placental macrophages, messages for all ligands except 4-1BBL were present. Transcripts for the 14 receptors to which the ligands bind, six of which contain death-domains (TNFR1, Fas, DR3, DR4, DR5, DR6), were also identified using RT-PCR. Term and first trimester placentae contained transcripts for all receptors except 4-1BB. Although term cytotrophoblasts lacked receptor mRNA encoding 4-1BB and OPG, term placental macrophages lacked DcR1 and OPG. Detection of nearly all the death-inducing TNF superfamily ligands and their receptors in human placentae implies that these powerful cytokines contribute to programmed or activated cell death in this organ.

4-1BB Ligand↗
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Human placentae: view from an immunological bias.

Human placentae form a major part of the interface between maternal and embryonic tissues. Placentae are morphologically complex organs that are lined with a trophoblastic tissue that provides anatomical constraints over which flows maternal blood. Maternal antibodies and immune cells thus contact the lining syncytiotrophoblast, and this paper considers some of the antigens that maternal immune components might encounter. The antigens have been grouped into those of unknown function, major histocompatibility antigens, and antigens of suspected function. The paper also details certain antigens of cytotrophoblasts. We discuss consequences of maternal immune responses to extraembryonic antigens and present evidence for amplification of these responses through the activation of hemostasis and fibrinolysis within the placenta and placental bed.

Autoantigens↗
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Amniochorion: immunologic aspects--a review.

Exploration of trophoblast cell gene expression may assist in elucidating the mechanisms responsible for allowing genetically disparate maternal and fetal cells to coexist during pregnancy. In the extraplacental membranes, chorionic cytotrophoblast cells are in direct contact with maternal cells. In theory, paternally derived major histocompatibility antigens (HLA) expressed by the chorion cells should stimulate a graft rejection response by the mother, yet there is no evidence for lymphocytic infiltration of the membranes. The results of recent in situ hybridization, Northern blotting, and other molecular studies suggest that failure of maternal immune cells to attack the membranes may be due to the ability of chorion cells selectively to transcribe class I HLA genes and/or to process the products of those genes differently from other types of cells. Inasmuch as some tumor cells exhibit patterns of class I HLA that are similar to those of trophoblast cells, regulation of class I HLA expression may be a general mechanism used by cells expressing non-self antigens (paternally derived HLA, tumor-specific antigens) to establish residency in host tissues.

Amnion↗
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Macrophages in human uteroplacental tissues: a review.

Macrophages are major cellular components of the uterus, the placenta, and the extra-placental membranes throughout pregnancy. Many macrophages in normal uteroplacental tissues are in an activated state as evidenced by their expression of class II major histocompatibility antigens. Activated macrophages are capable of synthesizing and releasing an impressive array of potent "monokines" and other molecules with dramatic effects on receptive cells. Macrophage activation levels can be further enhanced by exposure to either endotoxin from gram-negative organisms or to interferon-gamma from stimulated lymphocytes. Since prostaglandin E2 is one of the products of activated macrophages and can stimulate contraction of smooth muscle, macrophages may be responsible in part for the induction of preterm labor in cases of infection. Thus, understanding the conditions of uncomplicated pregnancy as well as the consequences of local infections requires exploration of the temporal, spatial, and functional characteristics of macrophages residing in uteroplacental tissues.

Animals↗
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Uterine natural killer cells: insights into lineage relationships and functions from studies of pregnancies in mutant and transgenic mice.

Mice expressing genetic alterations have been extremely valuable in providing insights into both the lineage relationships and functions of lymphohematopoietic cells. This approach has been applied to granulated lymphocytes that localize to implantation sites in the rodent uterus during pregnancy. Histological analyses of implantation sites collected from various mutant and transgenic mice over the course of gestation strongly support the conclusions that these granulated lymphocytes, previously named granulated metrial gland (GMG) cells, are natural killer (NK) cells and that they are essential for normal development of the placenta. Pregnancy-associated uterine NK (uNK) cells have limited lytic activity suggesting that their secretory products, particularly cytokines and matrix proteins, may be critical for normal placental maturation. This review will highlight information collected from pregnancies in mutant and transgenic mice that have contributed to the current understanding of functions of uNK cells during gestation.

Animals↗