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Y W Loke

Publications and source records attributed to Y W Loke.

At least 91 records · Page 5Linked to original sources
PubMed1991

CD3- leukocytes present in the human uterus during early placentation: phenotypic and morphologic characterization of the CD56++ population.

In this study, the CD3- LGL/NK cells present in the pregnant human uterus have been characterized. Phenotypic and morphologic analyses of decidual LGL revealed many similarities to the minor CD56bright+, CD16- subset in peripheral blood, but there were some important differences. The relative surface density of CD56+ is greatly increased on decidual LGL to 22x that found on the majority of CD56+ peripheral blood NK cells. The CD56bright+ cells in decidua show LGL morphology, whereas in peripheral blood, they are mainly agranular. Proliferation of CD56+ cells occurs predominantly during the nonpregnant secretory (luteal) phase, indicating these CD56+ uterine LGL do not migrate as terminally differentiated cells. The appearance of CD56+ cells was examined at the ultrastructural level using immunoelectron microscopy. Cells with phenotypic characteristics of decidual LGL occur in a higher percentage (1.11%) in the peripheral blood of women of reproductive age than in men (0.66%). On the basis of these results, it is proposed that the CD56bright+ uterine leukocytes represent a distinctive, hormonally regulated subset possibly adapted to control human placentation.

Adolescent↗
PubMed1991

Immunohistochemical localization of IL-1 alpha and IL-1 beta in normal human placenta.

Many reports show that interleukin 1 (IL-1) is produced by mouse and human placenta but the cell type that is responsible for this production has yet to be identified. For this reason we attempted to localize IL-1 alpha and IL-1 beta directly on formalin-fixed paraffin-embedded normal human placentae at different stages of pregnancy using immunohistochemical techniques and specific antibodies. The results obtained show that both IL-1 forms are localized to villous syncytiotrophoblast and to extravillous trophoblast, while villous cytotrophoblast and cytotrophoblast columns are unreactive. A gradual decrease of reactivity was observed with increasing gestation age for both IL-1 forms, but the staining for IL-1 beta was in all sections higher than for IL-1 alpha. Although the physiological role of IL-1 in pregnancy has yet to be established, the presence of this cytokine in the cells facing maternal blood and tissues suggests a possible involvement in the immunoregulation of fetal acceptance.

Female↗
PubMed1990

Identification of class I MHC mRNA in human first trimester trophoblast cells by in situ hybridization.

Special gestation-related regulatory mechanisms for the expression of class I Ag by trophoblast cells directly exposed to maternal blood and tissues may be required for semiallogeneic pregnancy to be successful. Analysis of class I MHC mRNA by in situ hybridization and class I MHC Ag by immunohistology has revealed two phenotypically distinct subpopulations of trophoblast cells in term placentas and extraplacental membranes. Trophoblast cells external to the placenta are mRNA +/Ag+. They contain class I mRNA and express class I Ag that differ serologically from HLA-A,B,C. In contrast, trophoblast cells forming the syncytial layer of placental villi are mRNA-/Ag-. By immunohistology, trophoblast cells in 1st trimester placental tissues are similar to those in term tissues. In our study, in situ hybridization was used to determine if patterns of trophoblast cell class I mRNA were the same or different. Trophoblast cells external to the placental villi in 1st trimester tissues contained class I mRNA as would be predicted from the results with term tissues. Unexpectedly, class I mRNA was found in villous trophoblast cells. Thus, these studies identified an mRNA+/Ag- trophoblast cell subpopulation. The results suggest that tissue-specific mechanisms may interfere with translation of class I mRNA in 1st trimester villous trophoblast cells and/or that the protein products of the mRNA are not identified by available mAb.

Female↗
PubMed1990

Uterine large granular lymphocytes: a possible role in embryonic implantation?

Leukocytes in endometrium and decidua are phenotypically and morphologically similar to granulated lymphocytes at other mucosal surfaces. Although their exact functions are not known, we suggest they may have a role in the control of implantation and the transformation of the uterine vasculature by trophoblast on which the blood supply to the fetoplacental unit depends.

Animals↗
PubMed1990

Human trophoblast cell resistance to decidual NK lysis is due to lack of NK target structure.

We have previously shown that human cultured trophoblast cells are resistant to lysis by natural killer (NK) cells from both peripheral blood and decidua although cells are present in decidua which do exhibit NK activity against K562(1). Using a cold-target inhibition assay and a single-cell conjugate assay we have now examined whether these trophoblast cells have NK target structures on their surfaces. Our findings indicate that first-trimester human trophoblast cells do not express surface structures recognized by decidual Leu19+ (CD56+) large granular lymphocytes (LGLs) isolated from human decidua. Immunostaining of the conjugates formed between decidual NK effectors and K562 cells confirmed that these effector cells are CD56+ LGLs.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1990

Human trophoblast and JEG choriocarcinoma cells are sensitive to lysis by IL-2-stimulated decidual NK cells.

Freshly isolated decidual large granular lymphocytes (LGL) show natural killer (NK) activity against K562 cells but not against normal human trophoblast. We now show that these decidual LGL proliferate in vitro in response to recombinant interleukin-2 (rIL-2) and that these rIL-2-stimulated cells acquire a broad cytolytic potential that is characteristic of lymphokine-activated killer (LAK) cells. Both fetal fibroblasts and JEG-3 choriocarcinoma cells are resistant to lysis by freshly isolated decidual effectors but are readily killed by IL-2-stimulated decidual LGL. The ability to kill these target cells is acquired after only 18 hr exposure to rIL-2. rIL-2-activated decidual LGL also kill cultured normal trophoblast cells but much lower levels of cytolysis were seen even after the effectors had been stimulated with rIL-2 for 4-6 days. The preferential killing of malignant over normal human trophoblast cells raises questions about the potential role of IL-2-activated decidual LGL in the control of unduly invasive or malignant trophoblast populations in vivo.

Antigens, CD↗
PubMed1990

Human trophoblast cells in culture express an unusual major histocompatibility complex class I-like antigen.

We present evidence that the trophoblast cells obtained from first trimester placentae by a culture method developed in our laboratory express a class I-like HLA antigen that is only sparsely distributed on the cell surface, lacks classical polymorphic determinants, and consists of heavy chains of lower molecular weight than those of classical HLA in association with beta 2-microglobulin (beta 2M). The latter two features are in general agreement with a previous report describing the nature of the HLA molecule on trophoblast disaggregated from term amniochorion. These cultured trophoblast cells could be useful for molecular studies of the unusual class I antigen, as well as for other in vitro experiments designed to mimic the in vivo local trophoblast-uterine interactions.

Antibodies, Monoclonal↗
PubMed1989

Early human decidual cells exhibit NK activity against the K562 cell line but not against first trimester trophoblast.

The susceptibility of cultured first trimester human trophoblast cells to lysis by NK cells has been studied. Trophoblast cells are resistant to lysis by NK cells from both peripheral blood and decidua. However, decidual cells extracted by enzymatic disaggregation do exhibit cytotoxicity against the NK-sensitive cell line K562. The relevance of these findings to successful implantation of the blastocyst is discussed.

Cell Separation↗
PubMed1989

Immunocytochemical characterization of the unusual large granular lymphocytes in human endometrium throughout the menstrual cycle.

Leukocyte populations were studied at all stages of the menstrual cycle using a panel of monoclonal antibodies to natural killer cells, T cells, B cells, and macrophages on frozen sections of endometrium. At the time of implantation (mid-secretory phase) the majority of leukocytes appear to be Leu19+, CD16-, Leu7-, CD2+, CD3-, CD5-, CD7-, and HLA DR- with the morphology of large granular lymphocytes. The numbers of these cells showed a marked increase in the mid-secretory phase. These cells exhibited similar phenotypic characteristics to those found in decidua. These findings, therefore, suggest that the recruitment of these large granular lymphocytes to the uterus is under hormonal control and is not a local response to the presence of invading trophoblast.

Antibodies, Monoclonal↗
PubMed1989

Laminin in human trophoblast--decidua interaction.

Laminin was localized by immunohistology to stromal cells of the human non-pregnant endometrium as well as to similar cells of the decidua. Only small amounts of laminin were detected during the proliferative phase, but significant quantities had accumulated by the mid-secretory phase which persisted in decidua if pregnancy occurred. This cyclical variation suggested hormonal control of laminin production. The presence of laminin could also be demonstrated in decidual cells in culture, most of which was intracellular or pericellular with very little liberated into the culture supernatant. Human first trimester trophoblast cells were observed to attach preferentially to laminin-coated surfaces in vitro. The role of laminin in trophoblast-decidua interaction in vivo is discussed.

Cell Adhesion↗
PubMed1987

Detection of trophoblast-like cells in maternal blood using specific monoclonal antibodies.

Mouse monoclonal antibodies reacting against membrane antigens expressed on syncytiotrophoblast (McAb H315), villous cytotrophoblast (McAb 18B/A5) and placental-type alkaline phosphatase-producing cells (McAb H317) were used in conjunction with flow cytometry to detect placental cells in the maternal circulation. H315 and H317-positive cells were found in uterine veins and peripheral blood of pregnant women, while cells reacting with McAb 18B/A5 were either absent or present in very low numbers.

Antibodies, Monoclonal↗
PubMed1985

Pregnant and pseudopregnant mice produce a low cytotoxic alloantibody response when challenged by fetal but not adult F1 alloantigens.

The tertiary cytotoxic alloantibody response of syngeneically pregnant, pseudopregnant and non-pregnant BALB/c mice immunised with semi-allogeneic lymphocytes from fetal and adult (CBA X BALB/c)F1 donors was investigated by the microcytotoxicity method. The pregnant and pseudopregnant animals showed a significantly lower response to fetal alloantigens compared to that towards adult alloantigens (P less than 0.001). In contrast, control non-pregnant recipients showed no diminution of response to fetal alloantigens. These observations suggest that the hormonal status of pregnancy, even in the absence of a conceptus, permits a low cytotoxicity antibody response when challenged specifically by fetal, but not when challenged by adult, F1 alloantigens.

Animals↗
PubMed1985

Human cytotrophoblast populations studied by monoclonal antibodies using single and double biotin-avidin-peroxidase immunocytochemistry.

Single and double biotin-avidin-peroxidase immunocytochemical methods in conjunction with an anti-trophoblast monoclonal antibody 18B/A5 and an anti-HLA-A,B,C monoclonal antibody W6/32 were used to study various human trophoblast populations. Several combinations of peroxidase substrates were tried in the double-labeling procedure. It was concluded that the use of 4-chloro-1 naphthol to develop the primary sequence peroxidase and of 3-amino-9-ethyl carbazole for the second sequence peroxidase was the most suitable. The significant findings were: Monoclonal antibody 18B/A5 proved to be a useful marker for villous as well as nonvillous trophoblast, which facilitated the identification of these cells particularly in the placental bed. The expression of MHC Class I antigens was not confined to extravillous trophoblast but these antigens were also demonstrable on the villous cytotrophoblast proliferating to form new primary villi. Double labeling revealed that many of these cells, particularly those furthest away from the mesenchymal core, expressed both trophoblast and HLA antigens as shown by a mixing of the colors produced by the two reaction products. A large number of these HLA-A,B,C, positive trophoblast cells were found to infiltrate deep into the uterine myometrium. The hypothesis was put forward that these fetal cells could be the ones that are responsible for maternal sensitization.

Antibodies, Monoclonal↗
PubMed1985

Immunocytochemical identification of cytotrophoblast from other mononuclear cell populations isolated from first-trimester human chorionic villi.

Trophoblast biologists are often uncertain as to what cell types they are investigating because the mononuclear cell populations prepared from trypsinization of human first-trimester chorionic villi are morphologically very similar. In the present study, immunocytochemical and phagocytic markers have been used to distinguish cytotrophoblast populations from cell types derived from the mesenchyme of the chorionic villus. Two anti-trophoblast monoclonal antibodies generated in our own laboratory (18B/A5 and 18A/C4) were found to be very efficient in identifying cytotrophoblast, which made up 35-40% of the cells in a smear. Most cytotrophoblast cells did not stain with a monoclonal anti-HLA-A,B,C antibody but a few cells (5%) were found to express both trophoblast and HLA-A,B,C antigens by a double-labelling technique. Endothelial cells from villous capillaries could be identified by a rabbit anti-factor VIII antibody. These cells formed 28% of the population in a cytospin smear. Macrophages from the villous mesenchyme were less readily separable as neither specific monoclonal antibodies nor localization of enzymes were found to be effective. However, these cells could be identified by their ability to phagocytose carmine. About 15% of the cells in a smear consisted of macrophages. The procedure described should prove useful in judging the efficiency of isolation methods from human placental cells.

Antibodies, Monoclonal↗