Immunocompetent cells in the endometrium of fetuses and children

U. Kämmerer1,3, L. Rieger1, M. Kapp1, J. Dietl1 and P. Ruck2

1 Department of Obstetrics and Gynaecology, University of Würzburg, Josef-Schneider-Strasse 4, D-97080 Würzburg and 2 Department of Pathology University of Tübingen, D-72076 Tübingen, Germany

3 To whom correspondence should be addressed. e-mail: frak057{at}mail.uni-wuerzburg.de


    Abstract
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
BACKGROUND: Although the immunocompetent cells of the adult human endometrium are well characterized, there is little information about these cells in the developing uterus. This study was undertaken to investigate the distribution of leukocyte subpopulations in the endometrium of fetuses and children. METHODS: Uterine tissue obtained at autopsy from fetuses (n = 11) and neonates/children (n = 9) between 17 weeks gestation and 51/2 years of age was investigated with antibodies against various leukocyte subsets by immunohistochemical staining techniques. RESULTS: The densities of CD45+ and CD68+ cells were significantly higher in the endometrium of neonates/children than in that of fetuses. CD14+ monocytes represented the largest leukocyte subpopulation in both groups. CD56+ natural killer cells and HLA-DR+ antigen-presenting cells were absent from fetal endometrium. There were no differences in density of CD3+ T cells between the two groups, but CD4+ T helper cells were found only in fetal endometrium. CONCLUSIONS: The endometrial leukocyte population of fetuses and small children is different from that seen in adult women. The appearance of CD56+ and HLA-DR+ cells in endometrium seems to be a post-natal event, which may be induced by the changes in hormone levels and/or the adaptation of the local immune system to the changing microenvironment.

Key words: development/fetal uterus/immunocompetent cells/immunohistochemistry/LGL


    Introduction
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Remarkably little is known about the distribution of immunocompetent cells in the developing human uterus, although such cells in the adult uterus are very well characterized (Bulmer et al., 1991Go). The numbers and distribution of the uterine leukocytes have been shown to vary during the menstrual cycle (Starkey et al., 1991Go). The population of CD45+ cells is concentrated predominantly in the stratum basale and increases premenstrually from 10–15% to 20–25% of all endometrial cells (Kamat and Isaacson, 1987Go). This rise is due mainly to an increase in the number of CD56+ uterine natural killer (NK) cells, the main subpopulation of endometrial lymphocytes in the secretory phase (Bulmer et al., 1991Go; Kodama et al., 1998Go). It has been suggested that uterine NK cells could act as cytotoxic effector cells or cytokine producing cells, and play an important role in implantation and placentation (King and Loke, 1991Go). The majority of non-NK immunocompetent cells in the endometrial stroma of the adult are macrophages and T cells. CD14+ macrophages account for ~30% of total endometrial leukocytes and their number shows little variation during the menstrual cycle (Bulmer et al., 1988Go). CD3+ T lymphocytes are found mainly in basal lymphoid aggregates, throughout the endometrial stroma and in the epithelium (Starkey et al., 1991Go). The vast majority of T cells (70%) belongs to the CD8+ subset (Vassiliadou and Bulmer, 1996Go) and their number remains stable throughout the menstrual cycle. B lymphocytes are very scanty in the human endometrium and are found scattered throughout the endometrium at all stages of the menstrual cycle (Starkey et al., 1991Go). Other immunocompetent cells that can be detected in small numbers are CD16+ NK cells (Starkey et al., 1988Go), CD83+ dendritic cells (Kammerer et al., 2000Go), neutrophils and mast cells (Mori et al., 1997Go).

The development of the human uterus during fetal life has only been described in a few reports, which have focused on morphological features. Huber and colleagues demonstrated that the formation of glands can be observed in the fetal human endometrium from the 20th week of gestation (Huber et al., 1971Go). Proliferation and differentiation of epithelial and stromal cells occur subsequently, and from the 33rd week of gestation secretory changes can be seen in the endometrium. Because of the withdrawal of maternal estrogens, regressive changes occur immediately after birth and a transitional type of endometrium without glandular activity appears (Huber et al., 1971Go). The only information about immunocompetent cells in the developing uterus pertains to mice. It has been shown that in the mouse, large granular lymphocyte (LGL)-1+ NK cells appear in the uterus 2–3 weeks after birth, unrelated to puberty or the microbial environment (Kiso et al., 1992Go). There are very few T cells in the murine uterus at birth, but their number reaches adult levels at ~3 weeks of age. As in humans, the majority of murine uterine CD3+ T cells are CD8+ (Croy et al., 1993Go).

As very little is known about the development of the immune system of the human uterus, this study was undertaken to investigate the distribution of the various different leukocyte subpopulations in the endometrium of human fetuses and children between 17 weeks gestation and 51/2 years of age.


    Materials and methods
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Tissue
All investigations were approved by the Ethics Committee of the Medical Faculty of the University of Würzburg, Germany. Parental consent for autopsy and histological examination of the tissue was obtained for all medical autopsies. Formalin-fixed, paraffin-embedded tissue was obtained from the Departments of Pathology of the Universities of Tübingen and Freiburg, and from the Department of Forensic Pathology, University of Würzburg. The uteri had been obtained at autopsy from 28 fetuses, neonates and children between 17 weeks gestation and 51/2 years of age. Tissue that exhibited autolytic changes or signs of inflammation, or failed to stain with Ki-67, was not included. The clinical data and the cause of death in the 20 cases in which the uterus was found to be suitable for inclusion in the study are listed in Table I.


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Table I. Clinical data of the 20 fetuses/children examined
 
Immunohistochemistry
The antibodies applied in the study are listed in Table II. Single, double and triple immunostaining, with one to three primary antibodies, was performed. Serial longitudinal sections were cut at 2 µm from paraffin-embedded uterine tissue specimens and placed onto 3-amino-propyltriethoxy-silane (APES; Roth, Karlsruhe, Germany) coated slides, dewaxed in xylene, rehydrated in graded ethanol and distilled water, and subjected to heat pretreatment by boiling in 0.2 mol/l sodium citrate buffer (pH 6.0) for 15 min in a microwave oven (750 W/s). The sections were treated with H2O2 prior to immunostaining to block endogenous peroxidase activity. For the single immunohistochemical staining procedure the sections were incubated with the primary antibody at the appropriate dilution, followed by the horseradish-peroxidase (HRP)-labelled LSAB kit system (biotin–streptavidin system; DAKO, Hamburg, Germany). 3,3'-diaminobenzidine (DAB; Sigma, Deisenhofen, Germany) was used as the chromogen. For double immunostaining the sections were treated with H2O2 between the two staining procedures to eliminate remaining HRP activity after the first colour reaction. The sections were then incubated with the second primary antibody, followed by incubation with the HRP-labelled LSAB kit system. For the second detection reaction the HistoGreen peroxidase substrate kit (Linaris, Wertheim, Germany), which gives a green reaction product, was used. For triple immunostaining we performed the same procedures as for double staining and used Vector SG (grey; Vector, Burlingame, CA, USA) as second chromogen, followed by HistoGreen as the third chromogen.


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Table II. Antibodies used for immunohistochemistry
 
The sections investigated did not contain uterine tissue alone, but also contained surrounding tissues such as blood vessels, ovaries and lymph nodes. The reactivity of the antibodies used was confirmed in these areas (internal positive controls). The sections were counterstained with haematoxylin, except for those subject to the triple immunostaining procedure.

‘Blocking’ immunohistochemistry
As staining of endothelial cells for HLA-DR and neural cells for CD56 would make it difficult to identify leukocytes reactive for these antigens, a blocking technique in which these cells were specifically stained first by antibodies against CD34 and S100 respectively, was employed. For this technique, the primary antibodies were used at 2x the normal concentrations and the chromogen (DAB) developed to a very high concentration of precipitate. This precipitate then completely covers the antigenic structures with the bound specific antibody, thus protecting this cellular structure from other antibodies. Subsequent staining with the second primary antibody will then produce no staining of the blocked structures.

Evaluation of results
To determine the average density of specific leukocyte subpopulations, fields containing only endometrium were randomly selected. The number of positive cells in three to 15 single fields (depending on the size of the uterus investigated) of 0.31 mm2 was determined at 250x magnification for each of the sections by two independent observers (L.R. and U.K.).

Potential differences in the findings of the two observers were investigated with Student’s t-test (significance set at P < 0.05); no statistically significant differences between their findings were noted (P > 0.9). The mean values for the various cell types in the two groups (fetuses, n = 11; neonates/children, n = 9) were analysed using the non-parametric Mann–Whitney U-test (significance set at P < 0.05).


    Results
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Histological examination revealed typical primary glands (invaginations of the surface epithelium), allowing identification of the endometrium, in all uterine tissue samples. The results of immunohistochemical staining are shown in Figure 1. The density of CD45+ cells was significantly higher (P = 0.025) in the endometrium of the neonates/children than in the fetuses. Amongst the various different leukocyte subpopulations only HLA-DR+ (P = 0.002), CD68+ (P = 0.025), CD4+ (P = 0.03) and CD56+ (P = 0.0002) cells were found to exhibit statistically significant differences in cell densities before and after birth, with the HLA-DR+ cells exhibiting the largest absolute difference. Cell density results are summarized in Figure 2.



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Figure 1. Immunohistochemical staining of immunocompetent cells in endometrial tissue. Specific staining is brown (DAB) or green (HistoGreen). Immunoreactive leukocytes are marked by arrows. All sections except (M) and (N) were counterstained by haematoxylin. (A) Staining with the common leukocyte antigen (CD45) shows positive cells to be scattered throughout the fetal endometrium. (BE) Only a few T cells reactive for CD3, CD4, CD7 or CD8 were seen. (F) CD14+ monocytes in neonatal endometrium. (G) Only very occasionally were CD16+ NK cells found in small endometrial vessels in children. (H) CD20+ B cells in neonatal endometrium. (I) In fetal endometrium, CD56 stained only nerve fibres (arrowhead). (J) in neonatal/childhood endometrium, annular staining for CD56 staining was found in single lymphocytes. (K) CD68+ macrophages in fetal endometrium. (L) Staining of numerous cells (arrows) and vessels (arrowhead) for HLA-DR in neonatal endometrium. (M and N) Double immunohistochemical staining for CD34 (brown) and HLA-DR (green) reveals HLA-DR+ leukocytes (arrows) in the endometrium of a neonate (N) but none in fetal endometrium (M). Vessels are marked by arrowheads; asterisk indicates surface epithelium, cytokeratin, grey (Vector SG), no counterstaining. (O and P) Double immunohistochemical staining for S100 protein (brown) and CD56 (green) reveals that there are no CD56+ LGL in the fetal endometrium (O) but clearly positive cells (arrows) are present in the endometrium of a child (P); vessels are marked by arrowheads. Bar = 100 µm.

 


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Figure 2. Graphs (scatterplots) showing the cell densities (cells/mm2) in the endometrium of fetuses (top) and neonates/children (bottom). An asterisk indicates cell surface markers that show a statistically significant difference in expression between fetal endometrium and neonatal/childhood endometrium. P-values: CD4 = 0.03; CD45 = 0.03; CD56 = 0.0002; CD68 = 0.025; HLA-DR = 0.002. Bar indicates median. Investigation of fetal endometrium for CD16+ cells was not possible due to the limited amount of tissue available.

 
Immunostaining with Ki-67 revealed high proliferative activity in the cells of the epithelium and the endometrial stroma in the fetal specimens (not shown). However, in the specimens from neonates/children only a few Ki-67-positive cells were detected. All the specimens investigated showed a high density of CD34+ blood vessels (Figure 1M and N).

The median number of endometrial CD45+ leukocytes was 18.6 cells/mm2 in fetal specimens and 30.6 cells/mm2 after birth (Figure 1A).

Lymphocytes
In most tissue specimens, moderate numbers of CD3+ cells were scattered irregularly throughout the endometrial stroma and epithelium (Figure 1B). The median number of CD3+ lymphocytes before and after birth was the same (3.2 cells/mm2).

A few CD4+ T-helper cells were seen, but only in the fetal uteri (median 1.3 cells/mm2; Figure 1C). The median number of CD7+ cells before and after birth was comparable (1.6 and 2.6 cells/mm2 respectively; Figure 1D). Only a few cytotoxic T cells (CD8+, median 0.6 cells/mm2 in both groups; Figure 1E) and B lymphocytes (CD20+, median 1.0 and 0.6 cells/mm2, respectively; Figure 1H) were found in the endometrial stroma in the uteri investigated.

Monocytes and mast cells
Endothelial cells were HLA-DR positive in all cases (Figure 1L), but HLA-DR-immunoreactive leukocytes were found only in neonates and children. Their median density was 19.5 cells/mm2, and they were often seen in clusters close to the surface epithelium (Figure 1N). In a double immunostaining procedure using the blocking technique with the antibody against CD34, no staining for HLA-DR was seen in the fetal endometrium, thus confirming the absence of HLA-DR+ leukocytes (Figure 1M). CD68+ cells could be detected scattered throughout the endometrial stroma in all cases (median 2.3 cells/mm2 in fetuses and 8.8 cells/mm2 after birth; Figure 1K), except one fetus at the 17th week of gestation, in which no endometrial CD68+ cells were found. A few mast cells were detected in some of the specimens (not shown). Owing to the limited number of sections per uterus in which endometrium was present, the evaluation of CD14+ cells was possible only in 14 of the 20 specimens (six fetuses, eight neonates/children). The median number of endometrial CD14+ cells was 5.85 cells/mm2 in fetuses, increasing to 28.4 cells/mm2 after birth (Figure 1F). Thus, CD14-immunoreactive cells represented the largest leukocyte subpopulation in both groups investigated.

CD56+ uterine NK cells
Single staining revealed marked reactivity for CD56 in most specimens. However, staining was restricted mainly to smooth muscle cells in the myometrium and nerve fibres (Figure 1I), and only in neonatal/childhood endometrium were some lymphocytes with annular staining detected (Figure 1J). After staining of the nerve fibres had been blocked by the antibody against S100 protein, no CD56 reactivity was observed in the fetal specimens (Figure 1O), indicating the absence of CD56+ NK cells. In contrast, a small number of CD56+ leukocytes was found scattered throughout the endometrium of neonates and children, with a median density of 3.4 cells/mm2 (Figure 1P). The density of CD56+ cells did not correlate with age (Figure 3). A very few CD16+ cells were found in the endometrium of neonates and children (median density 0.2 cells/mm2) and those cells were clearly located in small vessels (Figure 1G). Investigation of fetal endometrium for CD16+ cells was not possible due to the limited amount of tissue available.



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Figure 3. x–y plot of the density of CD56+ and HLA-DR+ cells in the endometrium of neonates and children in relation to age.

 

    Discussion
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
The distribution of immunocompetent cells in the developing uterus has so far been investigated only in the mouse model. As the immunological mechanisms involved in the regulation of the developing fetus are specific for each species, the data obtained are not necessarily applicable to the situation in man. Using immunohistochemical techniques, we examined the appearance of various different leukocyte subtypes in the endometrium of human fetuses and children up to 51/2 years of age.

The largest endometrial leukocyte populations between the 19th week of gestation and term were found to be CD14+ monocytes and CD68+ macrophages. Their proportions in relation to the total number of CD45+ bone marrow derived leukocytes were similar to those described in the adult endometrium (Bulmer et al., 1988Go). However, in contrast to the situation in neonates and children, staining for HLA-DR in the fetal endometrium was confined to vascular endothelium. Thus, at this stage of development of the fetal uterine immune system, CD68+ and CD14+ cells are negative for HLA-DR. These cells may be identical to the RFD7+/UCHM-1+/HLA-DR– majority of tissue macrophages, described by Janossy and colleagues, in the yolk sac and mesenchymal tissue of fetuses (Janossy et al., 1986Go). Since RFD7 is a marker for mature tissue macrophages (Collings et al., 1985Go), it is likely that this marker detects the same macrophage subpopulation as the CD68 antibody used in our study. However, in the endometrium of neonates and children a large number of HLA-DR+ cells with dendritic/macrophage-like morphology was found. The appearance of HLA-DR+ cells in the endometrium after birth may be due either to the induction of HLA-DR expression on the fetal monocytes/macrophages by mediators in the microenvironment or to the selective infiltration of the endometrium by HLA-DR+ cells. It is possible that interferon-{gamma} induces HLA-DR expression here, as this cytokine induces the expression of HLA-DR on fetal monocytes (Kelley et al., 1984Go) and is also known to play a key role in modulating host defences during delivery (Buonocore et al., 1995Go). On the other hand, foreign antigens or the changes in hormone levels might also induce infiltration of the endometrium by HLA-DR+ cells after birth.

CD3+ T cells accounted for 17.2% of the CD45+ endometrial cells before birth, and 10.5% after birth, the latter figure resembling that in adults (Starkey et al., 1991Go). In contrast to the situation in adults, only one-third of the CD3+ cells in the endometrium of fetuses and children were CD8+. CD4+ cells were found only in fetal endometrium and not after birth. The highest proportion of T cells were CD7+, consistent with the fact that CD7 is the earliest marker antigen expressed in T cell development (Haynes, 1990Go).

In contrast to the endometrium after the onset of puberty, where CD56+ uterine NK cells are the dominant lymphocyte population (Starkey et al., 1991Go), fetal endometrium was totally devoid of CD56+ uterine NK cells in all cases investigated, and neonatal/childhood endometrium contained only small numbers of these cells. This finding is surprising because CD56+ NK cells are found very early in the development of the immune system, and membrane CD3– CD56+ NK cells are identifiable in the fetal liver at around the 6th week of gestation (Phillips et al., 1992Go). Because only a limited amount of tissue was available in each case, there were not enough sections to perform double labelling procedures for CD56 and CD16. However, as the number of CD56+ cells was substantially higher than that of CD16+ cells, we conclude that the CD56+ cells correspond to the uterine CD56+ CD16– NK cells found in adult endometrium. In the mouse model, LGL-1+ NK cells seed the uterus during the first weeks of post-natal life, independent of onset of puberty and environmental factors (Kiso et al., 1992Go), and this study shows that this is also the case in humans. What triggers the first appearance of CD56+ uterine NK cells in human endometrium cannot be determined on the basis of the results of this study. However, it seems likely that these cells, which exhibit the same phenotype as a small proportion of NK cells in the peripheral blood, migrate into the endometrium at the onset of puberty, probably due to changes in the endometrial microenvironment induced by rising levels of steroid hormones. A recent study indicated that the high density of CD56+ NK in the uterus is not only due to homing mechanisms but, at least in pregnancy, also results from in situ expansion of these cells (Kammerer et al., 1999Go).

In summary, our data show that the leukocyte population in the endometrium of fetuses and small children is different to that in the endometrium of adult women. We demonstrated that the seeding of the endometrium with antigen-presenting HLA-DR+ cells and uterine NK cells is a post-natal event and may be induced by the changes in hormone levels occurring at this time and/or reflect the adaptation of the local immune system in the uterine mucosa to the change in circumstances from the almost sterile environment of the fetus to the normal environment of the newborn.


    Acknowledgements
 
We thank Drs S.Haehn and H.Kendziorra (Department of Pathology, University of Tuebingen, Germany), Dr C.Lang (Department of Forensic Pathology, University of Wuerzburg) and Professor N.Böhm (Department of Paediatric Pathology, University of Freiburg, Germany) for generously providing the uterine tissue and for helpful discussion. We thank Dr M.Ruck for help with the manuscript. This study was supported by a grant from the Federal Ministry of Education and Research (01KS9603) and the Interdisciplinary Center of Clinical Research Wuerzburg (IZKF) to U.K.


    References
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Bulmer, J.N., Lunny, D.P. and Hagin, S.V. (1988) Immunohistochemical characterization of stromal leucocytes in nonpregnant human endometrium. Am. J. Reprod. Immunol. Microbiol., 17, 83–90.[Medline]

Bulmer, J.N., Longfellow, M. and Ritson, A. (1991) Leukocytes and resident blood cells in endometrium. Ann. N. Y. Acad. Sci., 622, 57–68.[Medline]

Buonocore, G., De Filippo, M., Gioia, D., Picciolini, E., Luzzi, E., Bocci,V. and Bracci, R. (1995) Maternal and neonatal plasma cytokine levels in relation to mode of delivery. Biol. Neonate, 68, 104–110.[ISI][Medline]

Collings, L.A., Waters, M.F. and Poulter, L.W. (1985) The involvement of dendritic cells in the cutaneous lesions associated with tuberculoid and lepromatous leprosy. Clin. Exp. Immunol., 62, 458–467.[ISI][Medline]

Croy, B.A., Stewart, C.M., McBey, B.A. and Kiso, Y. (1993) An immunohistologic analysis of murine uterine T cells between birth and puberty. J. Reprod. Immunol., 23, 223–233.[CrossRef][ISI][Medline]

Haynes, B.F. (1990) Human thymic epithelium and T cell development: current issues and future directions. Thymus, 16, 143–157.[ISI][Medline]

Huber, A., Michael, S. and Feik, K. (1971) Functional changes in the fetal and infantile endometrium. Arch. Gynakol., 211, 583–594.[CrossRef][ISI][Medline]

Janossy, G., Bofill, M., Poulter, L.W., Rawlings, E., Burford, G.D., Navarrete, C., Ziegler, A. and Kelemen, E. (1986) Separate ontogeny of two macrophage-like accessory cell populations in the human fetus. J. Immunol., 136, 4354–4361.[Abstract/Free Full Text]

Kamat, B.R. and Isaacson, P.G. (1987) The immunocytochemical distribution of leukocytic subpopulations in human endometrium. Am. J. Pathol., 127, 66–73.[Abstract]

Kammerer, U., Marzusch, K., Krober, S., Ruck, P., Handgretinger, R. and Dietl, J. (1999) A subset of CD56+ large granular lymphocytes in first-trimester human decidua are proliferating cells. Fertil. Steril., 71, 74–79.[CrossRef][ISI][Medline]

Kammerer, U., Schoppet, M., McLellan, A.D., Kapp, M., Huppertz, H.I., Kampgen, E. and Dietl, J. (2000) Human decidua contains potent immunostimulatory CD83(+) dendritic cells. Am. J. Pathol., 157, 159–169.[Abstract/Free Full Text]

Kelley, V.E., Fiers, W. and Strom, T.B. (1984) Cloned human interferon-gamma, but not interferon-beta or -alpha, induces expression of HLA-DR determinants by fetal monocytes and myeloid leukemic cell lines. J. Immunol., 132, 240–245.[Abstract/Free Full Text]

King, A. and Loke, Y.W. (1991) On the nature and function of human uterine granular lymphocytes. Immunol. Today, 12, 432–435.[ISI][Medline]

Kiso, Y., McBey, B.A., Mason, L. and Croy, B.A. (1992) Histological assessment of the mouse uterus from birth to puberty for the appearance of LGL-1+ natural killer cells. Biol. Reprod., 47, 227–232.[Abstract]

Kodama, T., Hara, T., Okamoto, E., Kusunoki, Y. and Ohama, K. (1998) Characteristic changes of large granular lymphocytes that strongly express CD56 in endometrium during the menstrual cycle and early pregnancy. Hum. Reprod., 13, 1036–1043.[Abstract]

Mori, A., Zhai, Y.L., Toki, T., Nikaido, T. and Fujii, S. (1997) Distribution and heterogeneity of mast cells in the human uterus. Hum. Reprod., 12, 368–372.[Abstract]

Phillips, J.H., Hori, T., Nagler, A., Bhat, N., Spits, H. and Lanier, L.L. (1992) Ontogeny of human natural killer (NK) cells: fetal NK cells mediate cytolytic function and express cytoplasmic CD3 epsilon,delta proteins. J. Exp. Med., 175, 1055–1066.[Abstract]

Starkey, P.M., Sargent, I.L. and Redman, C.W. (1988) Cell populations in human early pregnancy decidua: characterization and isolation of large granular lymphocytes by flow cytometry. Immunology, 65, 129–134.[ISI][Medline]

Starkey, P.M., Clover, L.M. and Rees, M.C. (1991) Variation during the menstrual cycle of immune cell populations in human endometrium. Eur. J. Obstet. Gynecol. Reprod. Biol., 39, 203–207.[ISI][Medline]

Vassiliadou, N. and Bulmer, J.N. (1996) Quantitative analysis of T lymphocyte subsets in pregnant and nonpregnant human endometrium. Biol. Reprod., 55, 1017–1022.[Abstract]

Submitted on June 6, 2002; resubmitted on November 14, 2002; accepted on January 30, 2003.





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