Cell-mediated immunity imbalance in pregnancy-induced hypertension

The central role of natural killer cells in preeclampsia

Preeclampsia (PE) is a disease that is unique to pregnancy and affects multiple systems. It can lead to maternal and perinatal mortality. The precise etiology of PE is unclear. Patients with PE may have systemic or local immune abnormalities. A group of researchers has proposed that the immune communication between the fetus and mother is primarily moderated by natural killer (NK) cells as opposed to T cells, since NK cells are the most abundant immune cells in the uterus. This review examines the immunological roles of NK cells in the pathogenesis of PE. Our aim is to provide obstetricians with a comprehensive and updated research progress report on NK cells in PE patients. It has been reported that decidual NK (dNK) cells contribute to the process of uterine spiral artery remodeling and can modulate trophoblast invasion. Additionally, dNK cells can stimulate fetal growth and regulate delivery. It appears that the count or proportion of circulating NK cells is elevated in patients with or at risk for PE. Changes in the number or function of dNK cells may be the cause of PE. The Th1/Th2 equilibrium in PE has gradually shifted to an NK1/NK2 equilibrium based on cytokine production. An improper combination of killer cell immunoglobulin-like receptor (KIR) and human leukocyte antigen (HLA)-C may lead to insufficient activation of dNK cells, thereby causing PE. In the etiology of PE, NK cells appear to exert a central effect in both peripheral blood and the maternal-fetal interface. To maintain immune equilibrium both locally and systemically, it is necessary to take therapeutic measures directed at NK cells.

Lymphocyte sub-populations in gestational diabetes

PROBLEM

We hypothesize that the normal immunologic responses by the maternal immune system during pregnancy are not as well-regulated in gestational diabetes (GD) patients as in healthy pregnant women.

METHOD OF STUDY

Using two-color flow cytometry we evaluated frequencies of peripheral blood lymphocytes in 20 GD patients being treated with insulin; 43 GD patients treated with dietary therapy but no insulin; 44 women experiencing normal pregnancies; and 48 non-pregnant women.

RESULTS

When compared with healthy pregnant women, both GD cohorts showed higher percentages CD4(+)CD25(+) (P < 0.05), CD4(+)CD45RO(+) (P < 0.05) and CD4(+)CD29(+) (P < 0.01) but lower percentages of CD4(+)CD45RA(+) (P < 0.05). Higher percentages of the activated phenotypes CD8(+)CD25(+) and CD8(+)HLA-DR(+) cells in the diet-treated cohort and CD4(+)HLA-DR(+) cells in insulin-treated GB cohort, were observed compared with healthy pregnant subjects (P < 0.05).

CONCLUSIONS

Expanded populations of activated peripheral blood T cells are associated with GD, suggesting that normal maternal immunosuppression is less effective in GD-afflicted women.

Studies on activity of NK cells in preeclampsia patients

The activity of the NK cells in patients with preeclampsia was studied to investigate the pathogenesis of preeclampsia. By using MTT and 51Cr releasing technique, the proliferation and killing ability of the NK cells in maternal and umbilical blood from preeclampsia patients (n = 18) and normal third trimester pregnant women (n = 18) were detected. The NK-92 cell line was as the positive control. The results showed that the NK cell counts of umbilical blood in preeclampsia patients and normal third trimester pregnant women were significantly greater than those of maternal blood (both P<0.05). Compared with that in normal third trimester pregnant women, the proliferative ability of the NK cells in preeclampsia patients was apparently increased (P<0.05). Compared with that in maternal blood, the proliferative ability of the NK cells in umbilical blood from both preeclampsia patients and normal third trimester pregnant women was dramatically increased. The killing ability of the NK cells in preeclampsia patients was significantly higher than that in normal third trimester pregnant women (P <0.05). It was suggested that both number and function of the NK cells in preeclampsia women were increased, and that in umbilical blood was greater than that in maternal blood, speculating that the function of the NK cells may affect the maintenance of the maternal and fetal immune tolerance during pregnancy.

Lymphocyte subset distribution and cytokine secretion in third trimester decidua in normal pregnancy and preeclampsia

BACKGROUND

Excessive Th1 activity in peripheral blood plays a probable role in the pathogenesis of preeclampsia. The aim of the study was to investigate whether disturbed local immune reactions are also present in decidua.

METHODS

Flow cytometric analysis of CD3, CD19, CD56/CD16, CD4, CD8, CD4/CD29, CD4/CD45RA, CD4/CD45RO, CD8/CD28, CD3/CD69 lymphocyte subsets isolated from third trimester decidua of pregnants with preeclampsia (n=21) and pregnant controls (n=11) subjected to elective caesarean sections. Spontaneous and phytohemaglutynine stimulated "in vitro" secretion of IL-2, IL-4, IL-6, IL-10, IL-12, IFN-gamma and TGF-beta by decidual lymphocytes was studied by ELISA. For the statistical significance of differences between the groups the U Mann-Whitney test was performed (confidence interval P<0.05).

RESULTS

Preeclamptic patients were characterized with an increased percentage of the CD3-/CD56+CD16+, CD8+/CD28+ and decreased percentage of CD3+, CD19+, CD4+/CD45RA+ lymphocytes. The profile of secreted cytokines shifts in favor of Th1 activity (extremely high IFN-gamma and low IL-6 and IL-10 secretion). Decidual IL-12 secretion in preeclamptic patients is decreased compared to controls.

CONCLUSION

Changes in NK and T lymphocyte subsets followed with Th1 cytokine IFN-gamma over-activity, could affect local immunoregulatory mechanisms in third trimester decidua of preeclamptic patients.

The expressions of intracellular cytokines in the lymphocytes of preeclamptic patients

PURPOSE

The objective of the study was to investigate the intracellular expressions of T helper 1 (Th1) and Th2 cytokines in peripheral blood T lymhocytes and natural killer (NK) cells of patients with preeclampsia and women with uncomplicated pregnancy.

METHOD OF STUDY

Blood samples were taken from 20 patients with preeclampsia and 16 healthy pregnant women. Mononuclear cells were isolated from peripheral blood and stimulated for 5 hr at 37 degrees C and 5% CO2. Next, the cells were stained with antibodies against surface markers of T-cell subsets and NK cells. After fixation and permeabilization processes, the cells were stained with antibodies against intracellular cytokines--interleukin-2 (Il-2) and interferon-gamma (IFN-gamma) as well as Il-10 and Il-4. The intracellular expressions of Th1 and Th2 cytokines were determined using the flow cytometric method. Statistical analysis was performed using Mann-Whitney U-test.

RESULTS

We found that in patients with preeclampsia the expressions of Il-2 were significantly higher when compared with women with uncomplicated pregnancy. Furthermore, in the group of patients with preeclampsia the expressions of Il-2 were higher in T CD 8+ lymphocytes than in T CD4+ cells. The expressions of IFN-gamma did not differ in CD4+ cells and CD8+ cells in both studied groups but they were higher in NK cells in the study group. The expressions of Il-10 were lower in lymphocytes of preeclamptic patients when compared with controls. The expressions of Il-4 did not differ in both studied groups.

CONCLUSIONS

These results suggest that in patients with preeclampsia there is Th1/Th2 imbalance, with predominant Th1 immunity.

The expression and concentrations of Fas/APO-1 (CD95) antigen in patients with severe pre-eclampsia

PROBLEM

Apoptosis has been proposed as a mechanism for maintaining homeostasis in the immune system. Activated lymphocytes are removed by a Fas/FasL-mediated programmed cell death process called activation induced cell death (AICD). The aim of the study was to investigate surface Fas antigen (APO-1, CD95) expression on T lymphocytes and NK cells and also soluble Fas antigen concentrations in pre-eclamptic patients and healthy pregnant women.

MATERIALS AND METHODS

Sixteen pre-eclamptic patients and 18 healthy pregnant women were studied. Peripheral blood lymphocytes were isolated, labeled by direct staining with anti-CD95 monoclonal antibodies and analyzed using the flow cytometric method. Furthermore, the concentrations of soluble CD95 molecule in serum of patients with severe pre-eclampsia and women with uncomplicated pregnancy were measured using ELISA method.

RESULTS

We found that Fas antigen expression and fluorescence intensity on T CD8+ lymphocytes were higher in patients with severe pre-eclampsia in comparison with healthy pregnant women (P<0.05). Furthermore, the concentrations of soluble CD95 molecule were higher in the group of pre-eclamptic patients when compared to controls (P<0.001).

CONCLUSIONS

These findings suggest that T CD8+ lymphocytes in patients with severe pre-eclampsia can be activated. Moreover, higher concentrations of soluble CD95 antigen can suggest altered possibilities to undergo Fas/FasL-mediated activation induced cell death process of lymphocytes in severe pre-eclampsia.

T helper 1- and T helper 2-type cytokine imbalance in pregnant women with pre-eclampsia

OBJECTIVES

The purpose of our study was to investigate T helper 1/T helper 2 balance in pregnant women with pre-eclampsia.

STUDY DESIGN

18 patients with pre-eclampsia and 20 healthy pregnant women were included in the study. Peripheral blood mononuclear cells (PBMC) were stimulated with phytohaemagglutinin (PHA) for 48 h. Cytokine: interleukin-2 (11-2), interferon-gamma (IFN-gamma) and interleukin-10 (I1-10) concentrations in culture supernatants were determined using the ELISA method. Statistical analysis was performed using a standard non-parametric Mann-Whitney U-test.

RESULTS

We found that in pre-eclamptic patients PHA-stimulated 11-2 and IFN-y production was significantly higher (P<0.001) and I1-10 production significantly lower (P<0.005) in comparison with the control group.

CONCLUSION

These results could suggest that there is Th1/Th2 imbalance in pre-eclamptic patients with predominant Th1-type immunity.

Increased T-helper-1-type immunity and decreased T-helper-2-type immunity in patients with preeclampsia

PROBLEM

To examine whether preeclampsia involves type-1 T-helper (TH1) immune hyperactivity.

METHOD OF STUDY

Expression of HLA-DR, a cell-surface marker of activation, was analyzed on CD3+, CD4+, and CD8+ T cells in 15 preeclamptic patients and 15 normal pregnant women using flow cytometry. Additionally, peripheral blood mononuclear cells from preeclamptic patients and normal pregnant women were cultured with or without phytohemagglutinin (PHA) stimulation, and interleukin (IL)-2, IL-4, interferon (IFN)-gamma, and tumor necrosis factor (TNF)-alpha concentrations were determined in the supernatant by immunoassays.

RESULTS

HLA-DR antigen was expressed more strongly on CD3+ T cells in preeclamptic patients than in normal subjects. In preeclampsia, HLA-DR was expressed more strongly in CD8+ T cells than in CD4- T cells. More TNF-alpha, IL-2, and IFN-gamma were produced by unstimulated and stimulated cultured peripheral blood mononuclear cells from preeclampsia patients than by those from normal subjects. TNF-alpha/IL-4, IL-2/IL-4, and IFN-gamma/IL-4 ratios were higher in preeclamptic patients than in the normal group. Significant positive correlations were observed between mean blood pressure and concentrations of the Th-1 type cytokines IL-2, IFN-gamma, and TNF-alpha.

CONCLUSION

Up-regulation of Th1 responses and down-regulation of Th2 responses occur in preeclampsia.

Lymphocyte subsets and mitogen stimulation of blood lymphocytes in preeclampsia

PROBLEM

The question of whether there are differences in systemic immune reactivity in severe preeclampsia compared with normal pregnancy was addressed.

METHOD OF STUDY

During the third trimester, blood samples were taken from 12 pregnant women with severe preeclampsia. Five of the preeclamptic pregnancies were analyzed separately because they were treated with dexamethasone before the blood samples were taken. The seven dexamethasone-treated preeclamptic pregnant women were analyzed and compared with six uncomplicated pregnancies. A control group consisted of 15 nonpregnant females. Lymphocyte subsets were identified by flow cytometry. The function of peripheral blood mononuclear cells (PBMCs) was studied as proliferative responses to mitogens alone and in combination with immunomodulating drugs.

RESULTS

An increased number of B lymphocytes (CD19+) (P < 0.05) and natural killer (NK) cells (P < 0.05) was noticed in severe preeclampsia compared with normal pregnancy. The proliferative response of PBMCs in phytohemagglutinin (PHA)-stimulated cultures in autologous serum from patients with severe preeclampsia was reduced (P < 0.05) compared with normal pregnancy. The addition of indomethacin and cimetidine significantly stimulated (P < 0.05) the proliferative responses. The enhancing effect of cimetidine was not found in dexamethasone-treated preeclamptic patients.

CONCLUSIONS

The presence of systemic immunosuppression in severe preeclampsia is demonstrated as a reduced proliferative response of PBMCs to PHA, which could be partly restituted by indomethacin or cimetidine, indicating immunosuppressor activity that is mediated by prostaglandin and histamine. Increased levels of B lymphocytes and NK cells were also noticed.