1 Departments of 1Obstetrics and Gynecology and 2 Microbiology, Faculty of Medicine, Kuwait University, and 3 Maternity Hospital, Kuwait
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Abstract |
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Key words: CD30/pregnancy/recurrent spontaneous abortion/Th1 cytokines/Th2 cytokines
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Introduction |
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Th1-type cytokines are detrimental to pregnancy, via direct embryotoxic activity, or via damage to the placental trophoblast or possibly by activating cells that are deleterious to the conceptus (Hill, 1991). TNF-
and IFN-
are cytotoxic to trophoblast cells (Yui et al., 1994
) and inhibit implantation of the mouse embryo (Haimovici et al., 1991
). The administration of TNF-
, IFN-
or IL-2 to normal pregnant mice causes abortions (Chaouat et al., 1990
). In contrast, Th2-type cytokine production may directly or indirectly contribute to the success of pregnancy, and normal pregnancy appears to be biased in favour of a Th2-dominant status (Wegmann et al., 1993
). IL-10, a Th2-type anti-inflammatory cytokine, has been shown to prevent fetal wastage in mice prone to fetal resorptions (Chaouat et al., 1995
). Thus, a Th2-bias in pregnancy may be indirectly conducive for pregnancy, by down-regulating potential Th1-type reactivity which appears to be associated with pregnancy failure (Wegmann et al., 1993
; Raghupathy, 1997
).
A few studies in humans have suggested a Th2-bias in normal pregnancy and a Th1-bias in a substantial proportion of women with unexplained recurrent spontaneous abortion (RSA). It has been shown (Hill et al., 1995) that peripheral blood mononuclear cells (PBMC) of normal pregnant women, when stimulated with trophoblast antigens, responded by producing IL-4 and IL-10, without the production of IFN-
and TNF-ß. Elevated concentrations of the Th1-type cytokines IL-2 and IFN-
have been reported in women with spontaneous abortions, upon stimulation of PBMC with antigen and mitogen (Marzi et al., 1996
). It has also been shown recently that stimulation of PBMC with mitogen (Makhseed et al., 1999
) and with autologous placental cells (Raghupathy et al., 1999
) results in increased production of Th2-type cytokines by women with a history of successful pregnancy, and in increased production of Th1-type cytokines by women with a history of unexplained RSA. Others (Piccinni et al., 1998
) have demonstrated decreased production of IL-4 and IL-10 by decidual T cells of women with unexplained recurrent abortions as compared with women with successful gestation. Taken together, these results indicate a distinct Th2-bias in normal pregnancy and a Th1-bias in women with unexplained RSA.
The objective of the present study was to determine whether the cytokine secretion patterns shown by maternal PBMC upon stimulation and at the maternalfetal interface in normal pregnancy and in RSA is also reflected by circulating concentrations of cytokines in the blood. To address this issue, we have measured the serum concentrations of selected Th1 and Th2 cytokines in normal pregnancy during gestation and at delivery, and also in women with a history of RSA at the time of abortion. We also report the concentrations of Th1 and Th2 cytokines in women who had a history of RSA but who had a successful pregnancy.
In addition, we have also determined the concentrations of soluble CD30 (sCD30) in the sera of the subjects under study. CD30 has been described as being preferentially expressed, and sCD30 preferentially released, by human T cells producing the Th2-type cytokines (Del Prete, 1995; Romagnani et al., 1995
). High concentrations of sCD30 have been found in a variety of disorders that are clearly Th2-mediated or Th2-dominated. Since pregnancy appears to be a Th2-biased condition it is likely that the skew towards Th2-bias seen in peripheral blood cells may be reflected by increased concentrations of sCD30 in the blood. Keeping this possibility in view, we have measured the concentrations of CD30 in the serum of women with a history of normal pregnancy, and in those with a history of RSA.
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Materials and methods |
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In addition to these two groups, a third set of patients was also followed; this group comprised 39 women with a history of recurrent abortion but who had a successful pregnancy. This group of women with a history of RSA followed by a normal pregnancy were termed RSAN. Like the women in the RSA group, these women had had three previous consecutive spontaneous abortions and one successful pregnancy, and were incorporated into this study during normal pregnancy; these women each went on to have a successful gestation.
This study was approved by the ethics committee of our institution. Blood was collected by venipuncture and serum isolated shortly thereafter. Normal pregnant women provided blood samples at the three trimesters and at delivery, while women with unexplained RSA provided blood samples at the time of abortion.
Measurement of serum cytokines
Concentrations of the cytokines IL-2, IL-4, IL-5, IL-6, IL-10, TNF-, TNF-ß and IFN-
were measured using enzyme-linked immunosorbent assays (ELISA). All kits except the TNF-ß detection kit were obtained from Immunotech (Marseilles, France); TNF-ß kits were obtained from R & D Systems (Minneapolis, MN, USA). The manufacturers' protocols were followed, and recombinant reference cytokine samples served as positive controls for calibration. Each serum sample was monitored in triplicate in blinded fashion so that the persons conducting the ELISA were not aware of the source of samples under test. The sensitivity of each of the cytokine assays was: 5 pg/ml for IL-4, 1 pg/ml for IL-5, 3 pg/ml for IL-6, 5 pg/ml for IL-10, 5 pg/ml for IL-2, 3 pg/ml for IFN-
, 10 pg/ml for TNF-
and 7 pg/ml for TNF-ß.
Measurement of soluble CD30 concentrations
Soluble CD30 was detected using a mouse monoclonal antibody sandwich ELISA (DAKO, Glostrup, Denmark) using simultaneous incubation of serum samples and conjugate in antibody-coated microwells. The detection limit of this assay was 1 U/ml.
Statistical analyses
The non-parametric MannWhitney U-test was used for statistical comparison of cytokine levels. The Z-test of proportions was used to compare the incidence of cytokines in the two groups of subjects.
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Results |
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Serum IL-6 concentrations
During normal pregnancy, serum IL-6 concentrations did not vary significantly in the three trimesters, but were statistically significantly higher at delivery than in the first trimester (P = 0.01), at the second trimester (P = 0.05) and at the third trimester (P = 0.02) (Figure 1). The incidence of detectable IL-6 was also higher at delivery than at different stages in gestation, as tested by the Z-test of proportions (P = 0.0001) (Figure 2
).
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Serum IL-10 concentrations
IL-10 was not detectable in any of the sera during gestation, but was detected in the serum at the time of delivery. IL-10 was detected in 75% of the sera from women at normal delivery, but in only 46% of the women with RSA (Figure 2); this difference was statistically significant (P = 0.01). IL-10 concentrations were statistically significantly higher in the normal delivery group than in the RSA group (P = 0.02) (Figure 1
).
Serum IFN- concentrations
IFN- was also detectable in the sera of normal pregnant women at different stages of gestation (68% incidence in the first trimester, 54% in the second, 57% in the third, and 53% at delivery) and in women undergoing RSA (57%). There were no statistically significant differences in the concentrations (Figure 1
) and the incidence (Figure 2
) of IFN-
at various stages of pregnancy, or between normal pregnant women and women undergoing RSA.
Serum TNF- concentrations
TNF- was detectable in 75% of the sera in all three trimesters of normal pregnancy, and at delivery. TNF-
was detectable in a higher proportion of women with RSA, but the difference was not statistically significant (Figure 2
). However, the concentration of TNF-
in the RSA group was statistically significantly higher when compared with normal pregnancy in the first trimester (P = 0.01) and at delivery (P = 0.03) (Figure 1
).
Concentrations of cytokines in women with a history of RSA followed by successful pregnancy (RSAN)
The objective of this part of the study was to determine the cytokine profiles of abortion-prone women who had successful pregnancy, and to compare the profiles with those in women with a history of RSA who subsequently had another abortion. In Figures 1 and 2, the filled bars represent the concentrations of cytokines seen in the RSA
N subgroup. In general, women with a previous history of abortion but with a successful pregnancy had higher concentrations of the Th2 cytokine IL-6 at delivery than did abortion-prone women who had another abortion (P < 0.0001). There was a trend towards higher concentrations of the Th2 cytokine IL-10 in the RSA
N group as compared with the RSA group, but the difference was not significant. In contrast, statistically significantly higher concentrations of the Th1 cytokine TNF-
were detected in the serum of women in the RSA
N group as compared with the RSA group. This would suggest that the concentrations of the beneficial Th2 cytokines were higher, and concentrations of the harmful Th1 cytokine TNF-
lower, in abortion-prone women who had a normal pregnancy as compared with abortion-prone women who had another abortion. Interestingly, the profile of IFN-
concentrations did not indicate a similar pattern; IFN-
concentrations were higher in women in the RSA
N group than the RSA group.
As can be seen in Figure 2, the incidence of IL-6 positivity was higher in the RSA
N group, while the incidence of TNF positivity was lower in the RSA
N group as compared with the RSA group.
Serum CD30 concentrations
Serum CD30 concentrations were measured in the first trimester and at delivery in normal pregnancy, and at the time of abortion in women with unexplained RSA. Median sCD30 concentrations were 26 IU/ml in the first trimester group, 31 IU/ml in the normal delivery group, and 39 IU/ml in women undergoing RSA; no statistically significant differences were apparent between these three groups.
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Discussion |
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Another rationale for investigating the presence of selected cytokines in the serum is derived from studies in our laboratory (Makhseed et al., 1999; Raghupathy et al., 1999
) and by others (Hill et al., 1995
; Marzi et al., 1996
) which indicate that peripheral blood lymphocytes of women with RSA secrete higher concentrations of certain Th1 cytokines and lower concentrations of Th2 cytokines upon stimulation with mitogen or antigen as compared with women with successful pregnancy. Thus, this study was designed to verify whether a similar profile might also be detected in the circulation. Other studies have described the concentrations of cytokines in the sera of women with normal pregnancy and abortions (Vassiliadis et al., 1998
), but the current study compares the concentrations of cytokines in women with unexplained recurrent abortions with those in normal pregnancy, as well as in women with a previous history of RSA who have had their first successful pregnancy.
While we were unable to detect IL-2, IL-4 and IL-5 in the sera tested, elevated concentrations of IL-2 in normal pregnancy as compared with non-pregnant controls have been reported (Favier et al., 1990). However, a substantial increase in IL-2 concentrations was found only in 13% of the cases studied. Others (Mallmann et al., 1991
) have reported the detection of lower concentrations of IL-2 in women with unexplained RSA as compared with those with successful pregnancy. There are no reports on the detection of IL-4 and IL-5 in the serum of pregnant women. However, significant changes have been reported in the expression of mRNA corresponding to IL-4, IL-6 and IFN-
in peripheral blood mononuclear cells of normal pregnant women using semi-quantitative reverse-transcriptionpolymerase chain reaction (RTPCR) (Tranchot-Diallo et al., 1997
).
We found that IL-6 was readily detectable in the sera of pregnant women starting from the first trimester, as has been shown previously by others (Opsjon et al., 1993; Austgulen et al., 1994
). These authors described a significant increase in IL-6 concentrations as pregnancy progressed from one trimester to the next, but this observation was not made in the present study. However, we did find significant increases in both the concentration of IL-6 and the incidence of raised serum IL-6 concentration at the time of delivery. While such human studies do not clearly indicate a cause-and-consequence between increased IL-6 concentrations and events associated with labour, studies in monkeys have shown that an increase in IL-6 concentrations precedes uterine contractions (Gravett, 1994
), suggesting that IL-6 may play a role in physiological mechanisms involved in uterine contractions and the propagation of labour. Thus, increased concentrations of IL-6 may reflect a systemic reaction in the mother, leading to labour and delivery. The IL-6 found in the serum may originate from the trophoblast (Kameda et al., 1990
). We found that IL-6 concentrations were lower in women with RSA than in those undergoing normal delivery; considering that IL-6 is a Th2-type cytokine and that normal pregnancy appears to be a Th2-biased condition, the absence of high concentrations of IL-6 in the serum of women with RSA might reflect a bias away from Th2-type reactivity and a shift towards Th1-dominance.
IL-10 plays a positive role in the prevention of spontaneous pregnancy failure in a mouse model; the injection of IL-10 into abortion-prone mice resulted in the prevention of fetal wastage (Chaouat et al., 1995). In our previous studies (Makhseed et al., 1999
; Raghupathy et al., 1999
) and in those of others (Hill et al., 1995
), IL-10 was produced at higher concentrations by PBMC of women with normal pregnancy than those with a history of unexplained RSA. Thus, IL-10 has emerged as an important Th2-type cytokine in the maintenance of normal pregnancy (Chaouat et al., 1996
). Since it is directly involved in down-regulating Th1-type activity by inhibiting IFN-
production, IL-10 has been proposed to play an important immunoregulatory role in pregnancy by maintaining a bias away from the detrimental Th1-type of reactivity (Chaouat et al., 1995
; Raghupathy, 1997
). We found higher concentrations of IL-10 at delivery than during any other stage of gestation tested, though the reasons for thisand its significancewere not readily understood. However, it is clear that increased production of IL-10 by maternal PBMC stimulated with mitogen (Makhseed et al., 1999
) and with placental/trophoblast antigen (Hill et al., 1995
; Raghupathy et al., 1999
) is mirrored by increased concentrations in the serum. It is of particular interest that we found increased concentrations of IL-10 in normal pregnancy, without concomitant increases in IL-4 and IL-5. These three cytokines show a remarkable correlation in expression, especially in mice (Mosmann and Sad, 1996
); however, other subsets of CD4+ T cells, such as the so-called Th10 subset, may exist which may produce IL-10 to the exclusion of IL-4 (Sundstedt et al., 1997
). Thus, we may have to consider the possibility of subsets other than Th1 and Th2.
While IFN- is detectable in the serum during gestation, at delivery and in women with RSA, we did not find a correlation between the concentrations of IFN-
and RSA, nor did we find any increased incidence of IFN-
-positivity among women undergoing RSA. We have detected TNF-
in the serum of a higher proportion of women with RSA than in those with normal pregnancy, and also at statistically significantly higher concentrations in women with RSA than at delivery or at the first trimester in normal pregnancy. It has been found (Mueller-Eckhardt et al., 1994
) that TNF-
concentrations were significantly higher in subjects who subsequently had spontaneous abortion; these authors' observation of elevated TNF-
concentrations even before the onset of pregnancy is indicative of immune dysregulation as a possible aetiological cause of abortion. Women at risk for premature pregnancy termination have been shown to have significantly higher serum concentrations of TNF-
than did healthy pregnant women (Szekeres-Bartho et al., 1996
). Elevated serum concentrations of TNF-
have also been described previously (Shaarawy and Nagui, 1997
), these authors suggesting that cytokines may be produced locally at the maternalfetal interface and diffuse or penetrate into the systemic circulation. In contrast, it has been reported (Schust and Hill, 1996
) that IL-2, IFN-
and IL-10 could not be detected in the serum of women early in pregnancy, and that while TNF-
was detectable, it did not correlate with the outcome of pregnancy. These authors suggest that such an apparent discrepancy might be attributed to the fact that they measured cytokine concentrations early in pregnancy (67 weeks), and not during the process of spontaneous abortion itself. The blood samples in our study were withdrawn at the time of abortion or normal delivery, and TNF-
concentrations were significantly higher at abortion than during normal delivery or in the first trimester. TNF-
has potent deleterious effects on pregnancy; administration to normal pregnant mice resulted in abortions (Chaouat et al., 1990
), programmed cell death of human trophoblast cells (Yui et al., 1994
), inhibition of the in-vitro proliferation ofand the production of human chorionic gonadotrophin (HCG) and progesterone bytrophoblast cells (Hill, 1992
), and placental injury in the rat (Silen et al., 1989
). TNF may exert such effects by causing necrosis of embryos or by causing thromboses of the blood vessels supplying the uterus. Indeed, it has been shown (Clark et al., 1998
) that abortion in a murine model of immunologically mediated pregnancy loss is mediated by Th1 cytokine-triggered thrombotic and inflammatory processes.
We have also studied women who are abortion-prone but who had a successful pregnancy (RSAN) in terms of maternal reactivity to mitogen and to autologous placental cells. We found that the cytokine secretion profiles indicated a higher Th2 bias and a lower Th1 bias in the RSA
N group as compared with the RSA group (M.Makhseed et al., unpublished observations). The serum data described in the present study mirror these observations to some extent, in that we found the concentrations and incidence of Th2 cytokines to be higher in RSA
N women than in the RSA group, and that the concentrations and incidence of TNF-
were higher in RSA than in RSA
N women.
In summary, we found higher concentrations of the Th2 cytokines IL-6 and IL-10 at normal delivery than in women with RSA and conversely, increased concentrations of TNF- in RSA as compared with normal pregnancy. While this study does not purport to show a cause-and-consequence relationship between circulating cytokines and pregnancy outcome, it partially supports the observations drawn from experiments on the cytokine secretion profiles of PBMC and decidual lymphocytes that normal pregnancy is Th2-biased and that Th1-type immunity correlates with recurrent abortions. However, serum profiles of cytokines do not completely mirror the secretion profiles of stimulated maternal lymphocytes in the range and concentrations of cytokines secreted. For example, mitogen-stimulated maternal PBMC from pregnant women with a history of successful pregnancy secrete higher concentrations of the Th2 cytokines IL-4, IL-5, IL-6 and IL-10 as compared with those from women with RSA, while PBMC from women with RSA secrete higher concentrations of the Th1 cytokines IL-2, IFN-
, TNF-
and TNF-ß (Makhseed et al., 1999
).
Since CD30 has been reported to be associated with Th2-type reactivity, we measured soluble CD30 in the serum of normal pregnant women and in women undergoing RSA. Surface CD30 is cleaved proteolytically, resulting in the release of the soluble form of the molecule (sCD30) by CD30-expressing cells (Smith, 1993). We speculated that we might find increased concentrations of sCD30 in normal pregnancy as compared to women with RSA, but a comparison of sCD30 concentrations indicated this not to be the case. In the present study we measured only soluble serum CD30 and not the density of CD30 on the surface of T cells; thus it is likely that there may well be an association between normal pregnancy and CD30 density on the cell surface. We should also point out that other workers have reported that CD30 expression is not related to differentiation into Th1- or Th2-type cells, and that it does not discriminate between these subsets (Hamann et al., 1996
). Thus, the fact that we did not find a correlation between CD30 concentrations and successful pregnancy does not necessarily have any bearing on the relationship between successful pregnancy and a Th2-bias. In any case, sCD30 does not seem to be a good prognostic marker for pregnancy outcome.
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Acknowledgments |
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Notes |
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References |
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Armstrong, D.T. and Chaouat, G. (1987) Effects of lymphokines on murine placental cell growth in vitro. Biol. Reprod., 40, 466474.[Abstract]
Athanassakis, I., Bleackley, R.C., Paetkau, V. et al. (1987) The immunostimulatory effect of T cells and T cell lymphokines on murine fetally-derived placental cells. J. Immunol., 138, 3744.
Austgulen, R., Lien, E., Liabakk, N.-B. et al. (1994) Increased levels of cytokines and cytokine activity modifiers in normal pregnancy. Eur. J. Obstet. Gynecol. Reprod. Biol., 57, 149155.[ISI][Medline]
Cacopardo, B., Nigro, L., Celesia, B.M. et al. (1998) Serum cytokines as predictors of clinical outcome in AIDS-related intestinal cryptosporidiosis. Ital. J. Gastroenterol. Hepatol., 30, 162166.[ISI][Medline]
Cesario, R. (1983) Interferon- in synovial fluid and serum of patients with rheumatic disease. J. Rheumatol., 10, 647651.[ISI][Medline]
Chaouat, G., Menu, E., Clark, D.A. et al. (1990) Control of fetal survival in CBAxDBA/2 mice by lymphokine therapy. J. Reprod. Fertil., 89, 447457.[Abstract]
Chaouat, G., Meliani, A.A., Martal, J. et al. (1995) IL-10 prevents naturally occurring fetal loss in the CBAxDBA/2 mating combination, and local defect in IL-10 production in this abortion-prone combination is corrected by in vitro injection of IFN-. J. Immunol., 154, 42614266.
Chaouat, G., Menu, E., de Smedt, D. et al. (1996) The emerging role of IL-10 in pregnancy. Am. J. Reprod. Immunol., 35, 325328.[ISI][Medline]
Clark, D.A., Chaouat, G., Arck, P.C. et al. (1998) Cytokine-dependent abortions in CBAxDBA/2 mice is mediated by the procoagulin fg12 pathway. J. Immunol., 160, 545553.
Del Prete, G. (1995) Preferential expression of CD30 by human CD4+ T cells producing Th2-type cytokines. FASEB J., 9, 8186.
Duff, J. (1988) Arthritis and interleukins. Br. J. Rheumatol., 27, 25.
Favier, R., Edelman, P., Mary, J.-Y. et al. (1990) Presence of elevated serum IL-2 levels in pregnant women. N. Engl. J. Med., 322, 270.[ISI][Medline]
Gravett, M.G. (1994) An experimental model for intraamniotic infection and preterm labor in rhesus monkeys. Am. J. Obstet. Gynecol., 171, 16601667.[ISI][Medline]
Haimovici, F., Hill, J.A. and Anderson, D.J. (1991) The effects of soluble products of activated lymphocytes and macrophages on blastocyst implantation events in vitro. Biol. Reprod., 44, 6976.[Abstract]
Hamann, D., Hilkens, C.M.U., Grogan, J.L. et al. (1996) CD30 expression does not discriminate between human Th1- and Th2-type T cells. J. Immunol., 156, 13871391.[Abstract]
Hamano, K., Gohra, H., Koda, H. et al. (1998) Increased serum interleukin-8: correlation with poor prognosis in patients with post-operative multiple organ failure. World J. Surg., 22, 10771081.[ISI][Medline]
Hedges, S.R. (1998) Cytokine and antibody responses in women infected with Neisseria gonorrhoeae: effects of concomitant infections. J. Infect. Dis., 178, 742751.[ISI][Medline]
Heresbach, D., Letourneur, J.P., Balion, I. et al. (1998) Value of early blood Th1-cytokine determination in predicting severity of acute pancreatitis. Scand. J. Gastroenterol., 33, 554560.[ISI][Medline]
Hill, J.A. (1991) Implications of cytokines in male and female sterility. In Chaouat, G. and Mowbray, J.F. (eds), Cellular and Molecular Biology of the Maternal-fetal Relationship. INSERM/John Libbey Eurotext, Paris, pp. 269275.
Hill, J.A. (1992) Cytokines considered critical in pregnancy. Am. J. Reprod. Immunol., 28,123126.[ISI][Medline]
Hill, J.A., Polgar, K. and Anderson, D.J. (1995) T helper 1-type cellular immunity to trophoblast in women with recurrent spontaneous abortions. JAMA, 273, 19331938.[Abstract]
Kameda, T., Matsuzaki, N., Sawai, K. et al. (1990) Production of interleukin 6 by normal human trophoblast. Placenta, 11, 205213.[ISI][Medline]
Kato, H., Kinoshita, T., Suzuki, S. et al. (1998) Production and effects of interleukin-6 and other cytokines in non-Hodgkins lymphoma. Leuk. Lymphoma, 29, 7179.[ISI][Medline]
Makhseed, M., Raghupathy, R., Azizieh, F. et al. (1999) Mitogen-induced cytokine responses of maternal lymphocytes suggest a differential Th-type bias in normal pregnancy and pregnancy failure. Am. J. Reprod. Immunol., 42, 273281.[ISI][Medline]
Mallmann, P., Mallmann, R. and Krebs, D. (1991) Determination of tumor necrosis factor alpha (TNF) and interleukin 2 (IL-2) in women with idiopathic recurrent miscarriage. Arch. Gynecol. Obstet., 249, 7378.[ISI][Medline]
Marzi, M., Vigano, A., Trabattoni, D. et al. (1996) Characterization of type 1 and type 2 cytokine production profile in physiologic and pathologic human pregnancy. Clin. Exp. Immunol., 106, 127132.[ISI][Medline]
Maury, C.D.J., Teppo, A.M., Repo, H. and Lahdevirta, J. (1988) Elevated levels of cachetin/tumor necrosis factor in patients with acquired immunodeficiency syndrome. Am. J. Med., 85, 289291.[ISI][Medline]
Miyao, Y., Yasue, H., Ogawa, H. et al. (1993) Elevated plasma interleukin-6 levels in patients with acute myocardial infarction. Am. Health J., 126, 12991304.
Mosmann, T.R. and Sad, S. (1996) The expanding universe of T-cell subsets. Immunol. Today, 17, 138146.[ISI][Medline]
Mueller-Eckhardt, G., Mallmann, P., Neppert, J. et al. (1994) Immunogenetic and serological investigations in nonpregnant and pregnant women with a history of recurrent spontaneous abortions. J. Reprod. Immunol., 27, 95109.[ISI][Medline]
Opsjon, S.L., Wathen, N.C., Tingulstad, S. et al. (1993) Tumor necrosis factor, interleukin-1 and interleukin-6 in normal human pregnancy. Am. J. Obstet. Gynecol., 169, 397404.[ISI][Medline]
Papi, M., Didona, B., De Pita, O. et al. (1998) Livedo vasculopathy versus small vessel vasculitis: cytological and platelet P-selectin studies. Arch. Dermatol., 134, 447452.
Pellicer, A., Albert, C., Mercader, A. et al. (1998) The follicular and endocrine environment in women with endometriosis: local and systemic cytokine production. Fertil. Steril., 70, 425431.[ISI][Medline]
Piccinni, M.-P., Beloni, L., Livi, C. et al. (1998) Defective production of both leukemia inhibitory factor and type 2 T-helper cytokines by decidual T cells in unexplained recurrent abortions. Nature Med., 9, 10201024.
Pisa, A. (1990) Serum tumor necrosis factor levels and disease in leprosy and leishmaniasis. J. Infect. Dis., 161, 988995.[ISI][Medline]
Raghupathy, R. (1997) Th1-type immunity is incompatible with successful pregnancy. Immunol. Today, 18, 478481.[ISI][Medline]
Raghupathy, R., Makhseed, M., Azizieh, F. et al. (1999) Maternal Th1- and Th2-type reactivity to placental antigens in normal human pregnancy and unexplained recurrent spontaneous abortions. Cell. Immunol., 196, 122130.[ISI][Medline]
Robertson, S.A., Seamark, R.F., Guilbert, L.J. and Wegmann, T.G. (1994) The role of cytokines in gestation. Crit. Rev. Immunol., 14, 239292.[ISI][Medline]
Roilides, E., Sein, T. and Schaufele, R. (1998) Increased serum concentrations of interleukin-10 in patients with hepatosplenic candidiasis. J. Infect. Dis., 178, 589592.[ISI][Medline]
Romagnani, S. (1994) Lymphokine production by human T cells in disease states. Annu. Rev. Immunol., 12, 227257.[ISI][Medline]
Romagnani, S., Del Prete, G., Maggi, E. et al. (1995) CD30 and type 2 T helper (Th2) responses. J. Leukoc. Biol., 57, 726730.[Abstract]
Schust, D.J. and Hill, J.A. (1996) Correlation of serum cytokine and adhesion molecule determinations with pregnancy outcome. J. Soc. Gynecol. Invest., 3, 259261.[ISI][Medline]
Shaarawy, M. and Nagui, A.R. (1997) Enhanced expression of cytokines may play a fundamental role in the mechanisms of immunologically mediated recurrent spontaneous abortion. Acta Obstet. Gynecol. Scand., 76, 205211.[ISI][Medline]
Silen, M.L., Firpo, A., Morgello, S. et al. (1989) Interleukin 1 and tumor necrosis factor
cause placental injury in the rat. Am. J. Pathol., 15, 239244.
Smith, C.A. (1993) CD30 antigen, a marker for Hodgkin's lymphoma, is a receptor whose ligand defines an emerging family of cytokines with homology to TNF. Cell, 73, 13491360.[ISI][Medline]
Sundstedt, A., Hoiden, I., Rosendahl, A. et al. (1997) Immunoregulatory role of IL-10 during superantigen-induced hyporesponsiveness in vivo. J. Immunol., 158, 180186.[Abstract]
Szekeres-Bartho, J., Faust, Z., Varga, P. et al. (1996) The immunological pregnancy protective effect of progesterone is manifested via controlling cytokine production. Am. J. Reprod. Immunol., 34, 348351.
Tranchot-Diallo, J., Gras, G., Parnet-Mathieu, F. et al. (1997) Modulations of cytokine expression in pregnant women. Am. J. Reprod. Immunol., 37, 215226.[ISI][Medline]
Udhammar, A., Sundqvist, K.G., Ellis, B. and Rantapera-Dahlqvist, S. (1998) Cytokines and adhesion molecules in patients with polymyalgia rheumatica. Br. J. Rheumatol., 37, 766769.[ISI][Medline]
Vassiliadis, S., Ranella, A., Papadimitriou, L. et al. (1998) Serum levels of pro- and anti-inflammatory cytokines in non-pregnant women, during pregnancy, labour and abortion. Mediators of Inflammation, 7, 6972.[ISI][Medline]
Waage, A., Habtensen, A. and Espevik, T. (1987) Association between TNF in serum and fatal outcome in patients with meningococcal disease. Lancet, i, 355356.
Wegmann, T.G., Lin, H., Guilbert, L. and Mosmann, T.R. (1993) Bidirectional cytokine interactions in the maternal-fetal relationship: is successful pregnancy a Th2 phenomenon? Immunol. Today, 14, 353356.[ISI][Medline]
Wright-Browne, V., Schnee, A.M., Jenkins, M.A. et al. (1998) Serum cytokine levels in infectious mononucleosis at diagnosis and convalescence. Leuk. Lymphoma, 30, 583589.[ISI][Medline]
Yui, J., Garcia-Lloret, M., Wegmann, T.G. and Guilbert, L. (1994) Cytotoxicity of tumor necrosis factor- (TNF-
) and gamma-interferon (IFN-
) against primary human placental trophoblasts. Placenta, 15, 819828.[ISI][Medline]
Submitted on February 10, 2000; accepted on May 22, 2000.