Expression of perforin by natural killer cells within first trimester endometrium in humans

Role of a KIR/HLA-C allorecognition system in pregnancy

Decidual natural killer (NK) cells are thought to play a significant role in the allorecognition mechanisms during pregnancy. Through their activating and inhibitory receptors they may recognize selectively class I HLA alleles expressed on invading trophoblast and provide self-signals to control NK responses, thus regulating the maternal immune response at the fetomatenal interface. Killer immunoglobulin-like receptors (KIR) constitute one of the families of class I MHC receptors which are expressed on NK cells. Their repertoire includes both activating and inhibitory receptors, most of which recognize specific epitopes on HLA-C molecules and can either activate NK cell responses or abort activating signals and inhibit NK cell functions. Since KIRs are expressed on decidual NK cells and the HLA-C molecules that they recognize are also expressed on invading trophoblast, KIR receptors may play a regulatory role in pregnancy by interacting with their trophoblastic HLA-C counterparts and providing trophoblast damage evading signals (KIR/HLA-C allorecognition system). Our hypothesis that the KIR/HLA-C system might be ineffective in some unsuccessful pregnancies, has been investigated in women with unexplained spontaneous abortions. Our results suggest that a limited maternal repertoire of inhibiting KIRs (inhKIRs) and/or lack of maternal inhKIR-fetal HLA-C epitope matching may predispose to miscarriage.

Uterine natural killer cells in a three-dimensional tissue culture model to study trophoblast invasion

The high numbers of CD56(+) cells with natural killer (NK) functions present in the uterine mucosa during the late secretory phase of the menstrual cycle and during early pregnancy have been considered to be implicated in implantation and in the regulation of trophoblast invasion. A three-dimensional organ culture model was used to study the interactions of these uterine NK cells with Jeg-3 and BeWo choriocarcinoma cells as a model of the invasive trophoblast. For this purpose, fragments of endometrial and decidual tissue were put in close contact with multicellular spheroids of choriocarcinoma cells in small silicon funnels. After the formation of stable contacts, the confrontation cultures were transferred to spinner flasks, cultivated for up to 6 days, and prepared for immunohistochemistry. During 2 days of cocultivation, the first cells started to move forward into the stromal component of the confrontation culture as demonstrated by staining of the choriocarcinoma cells using anti-human cytokeratin. Invasion advanced until, after a total of 6 days, some choriocarcinoma cells had already penetrated deeply into the host tissue. After a cultivation period of 1 week, both the endometrial and decidual tissue fragments still contained several CD56(+) uterine NK cells, and some of them expressed the proliferation-associated marker Ki-67 without any exogenous activation. A few CD56(+) cells were found directly at the invasion front, as well as between the choriocarcinoma cells. These cells also contained the cytolytic granule protein perforin indicating a migration of NK cells with cytolytic potential toward the potentially invasive cells. In conclusion, this human system closely resembles the in vivo conditions during trophoblast invasion and provides an appropriate in vitro model for studying dynamic processes involving various cell types during trophoblast invasion at the experimental level. Moreover, it enables us to study the effects of cytokines and growth factors that possibly regulate trophoblast invasion.

Cytokine network at the feto-maternal interface

There is much evidence that cytokines play a very important role in the maintenance of pregnancy by modulating immune and endocrine systems. Placental tissue produces cytokines and hormones that are essential to the regulation of the feto-maternal unit. Decidual lymphocytes express cell surface markers for activation, such as CD69 and HLA-DR, and these cells secrete many cytokines. Recent studies suggested that in pregnant women, cytokines produced by Th2 cells predominate over those produced by Th1 cells, resulting in the maintenance of pregnancy. This review article focuses on the unique cytokine network at the feto-maternal interface in humans. Recently, we demonstrated that Th2 cells were dominant within the decidua in early pregnancy in humans. The Th2-derived cytokines, IL-4 and IL-6, induce the release of hCG from trophoblasts, and the hCG stimulate progesterone production from corpus luteum in pregnancy. Progesterone stimulates the secretion of Th2 and reduces the secretion of Th1 cytokines. Thus, Th2 type cytokines appear to contribute to the maintenance of pregnancy by controlling the immune and endocrine systems and promoting the function of the trophoblasts at the implantation site.

Perforin-expressing lymphocytes in peripheral blood and decidua of human first-trimester pathological pregnancies

PROBLEM

We have shown previously that the decidua of first-trimester human pregnancy is heavily infiltrated with perforin-positive cells. The aim was to detect expression of perforin in both decidual lymphocytes (DL) and peripheral blood lymphocytes (PBL) in the first trimester of pathological pregnancies: Anembryonic pregnancy and missed abortion.

METHOD

Decidual tissue from a normal pregnancy group and from pathological pregnancies was obtained by vaginal curettage. Perforin (an intracellular antigen) and the cell surface antigens CD3, CD4, CD8, CD16, CD56, CD11c, and CD45RA were quantified simultaneously by flow cytometric analysis.

RESULTS

In the missed abortion group, we found: 1) a relative decrease in the frequency of both CD4+P+ cells and CD56+P+ cells as well as the mean fluorescence intensity for perforin; 2) a relative increase of CD16+P+ PBL cells; and 3) a relative increase of CD4+ cells in PBL compared with anembryonic pregnancy and normal pregnancy. There was also a significant relative decrease in the proportion of CD4+ and CD8+ cells among perforin-positive PBL in both anembryonic pregnancy and missed abortion.

CONCLUSION

Our results show that significant decreases in the prevalence of perforin-positive lymphoid cells, their subpopulations, and mean fluorescence intensity for perforin are associated with pregnancy failure.

Local expression of IFN-gamma mRNA in skin lesions of patients with dermatophytosis

Delayed type hypersensitivity (DTH) response to dermatophyte antigens is one of the host defense mechanisms in dermatophytosis. Skin lesions of dermatophytosis were examined for the cytokine mRNAs expression using the reverse transcriptase/polymerase chain reaction (RT-PCR) method. Interferon-gamma (IFN-gamma) mRNA was expressed in all of the dermatophytosis lesions. IFN-gamma plays an important role in the effector phase of the DTH reaction. Therefore, these findings indicate that DTH response is elicited in the skin lesions with dermatophytosis.

Inhibition by verapamil of cholecystokinin-enhancement of pancreatic carcinogenesis induced by azaserine in Wistar rats

The effect of a calcium channel blocker, verapamil, on cholecystokinin (CCK)-enhancement of pancreatic carcinogenesis induced by azaserine was investigated in Wistar rats. During and after 25 weekly injections of azaserine, each rat received alternate-day injections of CCK-octapeptide (CCK-8) and/or verapamil. Carcinogen-induced pancreatic lesions staining for mu class glutathione S-transferase (GST-mu) were examined histochemically at week 62. Prolonged administration of CCK-8 significantly increased the number and area as a percentage of parenchyma of GST-mu-positive lesions. Concomitant administration of verapamil significantly attenuated the enhancing effect of CCK-8. These findings indicate that calcium may play an important role in CCK-enhancement of pancreatic carcinogenesis.

Perforin expression in peripheral blood lymphocytes in rejecting and tolerant kidney transplant recipients

Perforin (P) is a cytolytic molecule expressed in the granules of cytolytic T cells and natural killer cells. Although cytotoxic cells have been implicated in graft rejection, no prospective clinical study has been published that examines the dynamics of perforin expressing cells in peripheral blood lymphocytes of transplanted patients. The cytofluorimetric assay developed in our laboratory previously for the simultaneous detection of intracellular perforin together with cell surface molecules was used for posttransplantation monitoring of patients, for the assessment of the efficiency of immunosuppressive treatment, and for the prediction of acute kidney transplant rejection and the stability of tolerance to long lived kidney transplants. Immunosuppression for the purpose of allotransplantation causes a decline in the number of perforin-expressing cells in peripheral blood. In contrast, in patients with clinical signs of acute rejection, the total number of perforin-expressing lymphocytes was increased in comparison with nonrejecting patients. Analyzing perforin-expressing subsets, rejection crises were accompanied by a relative decrease of perforin expression in the CD4+ subpopulation while increasing in the CD8+ subset. In the CD56+ and CD16+ NK subpopulations changes in perforin expression were mixed. In nonrejecting patients the ratio of perforin expression in CD4+ cells was high compared with CD8+ cells. Intensive therapy of acute rejection episodes with high doses of corticosteroids (methylprednisolonet [Solumedrol] bolus) strongly and significantly decreased the percentage of both, the subpopulations of perforin-positive T cells and the subpopulation of CD56+P+ NK cells. The lowest level of perforin expression, including low frequencies of perforin among CD8+ and CD4+ cells, was found in the group of patients tolerating transplanted kidneys for several years. These changes in perforin protein expression in peripheral blood can be used to discriminate between immunosuppressed patients who are immunologically quiescent and those who undergo transplant rejection. Our results confirm the hypothesis that cytotoxicity mediated by perforin may be an important effector mechanism in the rejection of allografted kidneys.

Characteristics of perforin expressing lymphocytes within the first trimester decidua of human pregnancy

PROBLEM

The number of perforin (P)-positive cells in decidua of pregnancy is larger than that observed in any other pathological condition. The aim was to investigate the distribution and the phenotype of P+ cells.

METHOD

Decidual tissue was obtained from the first trimester vaginal termination of pregnancy. Tissue distribution of P+ cells was analyzed by immunohistochemistry. The method for simultaneous measurement of P and cell surface is presented.

RESULTS

There is no difference in number and distribution of P+ cells between decidua basalis (DB) and decidua parietalis (DP). The percentage of P+ decidual lymphocytes (DL) is two times higher than in peripheral blood lymphocytes (PBL) (55% vs. 27%), and the prevalent phenotype is CD3- CD4- CD8- CD2+ (95%) CD11c+ (68%) and CD56+ (82%). CD56bright+ DL are also Pbright+ and this is the largest DL subpopulation (42.4% DL). Two different subpopulations of CD8+ DL exist: 1) CD8bright+, which are CD3+ CD56- P- and 2) CD8dim+, which are CD3- CD56+ P+.

CONCLUSION

P expressing DL are prevalently nonclassical NK cells (CD16-) with low cytolytic activity but fully equipped with potent cytolytic machinery (Pbright+). There are no classical cytotoxic lymphocytes (CTL) (CD3+ CD8+ P+) in the decidua, and all CD8+ P+ cells are CD3- CD56+. The number of P+ cells is even higher in DP in the vicinity of noninvasive trophoblast, than in DB.

Distribution of perforin-containing cells in normal and pregnant mice

Cytotoxic T lymphocytes (CTL) and natural killer (NK) cells elaborate a cytolytic protein named perforin or cytolysin. It was widely held that, in vivo, high quantities of perforin are not present in resting lymphocytes and are usually produced only by activated lymphocytes found under pathological conditions. Until now, only one tissue was known to synthesize abundant quantities of perforin under nonpathological conditions, the uterus during pregnancy. To investigate the possibility that perforin might also be synthesized by other tissues, several tissues besides the uterus from pregnant and normal mice were tested by immunofluorescence and immunoperoxidase for the presence of perforin. The tissues studied were the ears, brain, nasal epithelium, tongue, salivary gland, larynx, thymus, stomach, liver, spleen, small intestine, and lymph nodes; two cell populations with different sizes and levels of perforin expression were found. Large cells, displaying the NK cell phenotype and expressing high levels of perforin, were detected not only in the uterus but also in the salivary gland and lungs of pregnant mice. Small cells, expressing low levels of perforin, were detected mainly in the stomach and small intestine, and they were expressed in both pregnant and normal mice. Taken together, these results imply that perforin-containing cells exist in vivo under nonpathological conditions, and that the immune system is endowed with heretofore unknown mechanisms for stimulating the activation of NK cells in a limited number of tissues during pregnancy.

Elevated endometrial natural killer cell activity during early porcine pregnancy is conceptus-mediated

This study investigated an extended time course of endometrial NK cell activity during gestation and the mechanisms underlying changes in uterine NK cell activity in pigs. Endometrial tissues were collected from cyclic, pseudopregnant and pregnant nulliparous pigs on various days post-estrus, and from pigs 10 days after insemination with seminal plasma or killed spermatozoa. NK effector cells were isolated from each endometrial sample, size fractionated and tested for cytolytic activity against NK target cells (K562) using chromium release assays and immunocytochemically for the frequency of perforin-positive cells. Various cell fractions showed different levels of NK activity and had different proportions of cells expressing perforin. Morphologically, cells in the fraction with maximal NK activity almost all showed typical lymphocyte size and shape. Substantially elevated NK cell activity was recorded in pregnant pigs on days 10 and 20 of gestation. By day 30, the cytolytic activity declined dramatically to an almost undetectable level. Very little activity was found in uterine cells isolated from cyclic, pseudopregnant, and seminal plasma or killed spermatozoa inseminated animals, and no differences were detected either between follicular and luteal phases of the estrous cycle or between different days of pseudopregnancy. These results indicate that elevated NK cell activity during early porcine pregnancy cannot be attributed to contributions from either the maternal systemic endocrine status or from components of boar semen. The changes in NK cell activity observed in porcine endometrial tissues during early pregnancy must therefore be associated with the actual presence of conceptuses.