Endometrial lymphoid tissue: an immunohistological study

Immunohistochemical study of immune cells in the bovine endometrium at different stages of the oestrous cycle

Normal uteri were collected from 34 maiden heifers at slaughter and their stage of the oestrous cycle was determined from the ovarian structures. Cells expressing major histocompatibility complex (MHC) class II were widely distributed in the epithelium and lamina propria of the endometrium and were the most abundant population studied. The expression of MHC class II increased in the endometrium during the follicular phase of the cycle. Macrophages occurred throughout the stratum compactum and stratum spongiosum and their density did not appear to vary with the stage of the cycle. CD4+ cells were found mainly in the stratum spongiosum, whereas CD8+ cells were present mainly within the luminal and glandular epithelia and in the stratum compactum. The density of the populations of CD4+ and CD8+ cells increased markedly during the mid-to-late luteal and follicular phases, respectively, of the cycle. In the endometrium lymphoid aggregates were observed only rarely and no B cells were identified in any of the heifers.

Effects of progestogens on human endometrium

The effect of progestogens on endometrium depends on the dosage, duration of exposure, the type of progestogen, and the presence or absence of estrogen. Mechanisms of progestogen action in endometrium are mainly expressed through the binding of hormone to specific nuclear receptors. Exogenous progestogens seem to influence the hypothalamic-pituitary-ovarian-endometrial axis differently in different individuals. Endogenous hormones resulting from ovarian secretion have effects on the endometrium independent of, and in combination with, exogenous progestogens. Endometrial morphological changes with progestogens vary from suppression of endometrial glandular growth, through stromal decidualization and leukocytic infiltration to glandular atrophy and stromal focal necrosis. In a minority of cases resulting from very prolonged treatment connective tissue fibers increase to some degree and may be accompanied by endometrial fibrosis and calcification. Clinical and histological data have demonstrated that all these changes, including fibrosis and calcification, return to normal in a short period after discontinuing treatment. Endometrial changes during progestogen therapy are often accompanied by leukocyte infiltration, especially when necrosis occurs. White blood cells constitute an important component of normal endometrium. The number and the type of leukocytes change during the normal menstrual cycle apparently related to circulating ovarian hormonal changes. Exogenous progestogens also influence white blood cells, by increasing total numbers and certain specific cell types. Changes in endometrial white blood cell function as a consequence of exogenous progestogens are unclear, but it is possible that the increase of leukocyte infiltration resulting from exogenous progestogens plays an important role in evoking progestational endometrial necrosis.

Regulatory roles of IFN-gamma in human endometrium

Available data suggest that several microenvironments exist within the complex structure of human endometrium. Predecidual reaction which is associated with the expression of VLA-1 and alpha 1 PEG first appears in the stromal cells around the spiral arteries. Expression of Ber-EP4 is limited to a distinct group of stromal cells that reside around glands and underneath surface epithelium. A distinctly different group of stromal cells that surround lymphoid cells express HLA-DR molecules. The proliferative activity of endometrial epithelium is markedly higher in the upper functionalis and is gradually diminished towards the basalis. In addition, several proteins, including HLA-DR and some members of the integrin family of molecules are strongly expressed in the basalis epithelium. The expression of these proteins in endometrial epithelium is gradually diminished towards the surface. The gradual rather than abrupt changes in the expression of proteins and proliferative activity across the length of endometrial epithelium argues against separation of endometrium into the distinct regions of basalis and functionalis. Rather, such distribution is in favor of existence of a polarized microenvironment in human endometrium. Emerging evidence suggests that the development of this microenvironment is mediated by T cells activated within lymphoid aggregates with consequent secretion of IFN-gamma. IFN-gamma regulates HLA-DR expression and proliferation of endometrial epithelium. Maximal impact of the cytokine is exerted in regions close to the source of cytokine with a gradual dissipation of the effect distant from this source. Therefore, this cytokine may be the prototype of a group of paracrine factors that induce a polarized microenvironment in human endometrium.

Cytokine regulation of cellular proliferation in endometriosis

OBJECTIVE

This study was designed (1) to characterize the resident leukocyte population in ectopic endometrium (EE), (2) to assess proliferative activity of cellular components in EE, (3) to assess whether resident leukocytes in EE express IFN gamma mRNA and (4) to demonstrate endometrial epithelial cell IFN gamma receptors in EE.

STUDY DESIGN

Biopsies of EE and normal eutopic endometrium (UE) were studied immunocytochemically using monoclonal antibodies specific for CD45 leukocyte common antigen, CD3 (a T cell marker), CD11c (a macrophage marker), and Ki67 (proliferation marker). Leukocyte types were identified immunocytochemically, followed by in situ hybridization to assess expression of IFN gamma mRNA. IFN gamma receptor expression was assessed by immunocytochemistry.

RESULTS

The percentage of scattered stromal cells staining for each CD marker was greater in EE than in UE. The proliferative activity of endometrial stromal cells and epithelial cells was significantly less in EE than in UE. The overall concentration of T cells and macrophages expressing IFN gamma mRNA was significantly greater in EE than in UE. The percentage of each leukocyte type expressing IFN gamma mRNA was also greater in EE than in UE, and IFN gamma receptors were present in glandular epithelium of EE.

CONCLUSIONS

These findings support a possible paracrine role for resident leukocytes and IFN gamma in regulating cell proliferation in endometriosis.

The effect of progesterone on the accumulation of leukocytes in the human endometrium

OBJECTIVE

Our purpose was to determine the role of progesterone on the number and type of leukocytes found in human endometrium.

STUDY DESIGN

Endometrial tissue was obtained from normally cycling women and from women receiving hormone replacement therapy for premature ovarian failure. All tissues were formalin fixed, sectioned, and stained with specific antibodies to leukocytes, T cells, B cells, and macrophages. Each tissue was also dated by means of published techniques. Quantitation was performed by counting all immunopositive cells in five high-powered fields. Data were compared by analysis of variance and Mann-Whitney U test.

RESULTS

Leukocytes increased from 31.1 to 99.1 per high-powered field (p = 0.0001), and T cells increased from 10.9 to 20.4 per high-powered field (p = 0.001) after 12 days of progesterone treatment of women with ovarian failure. Normally menstruating women in the late luteal phase had similar concentrations. Neither B cells nor macrophages were found to increase with progesterone treatment.

CONCLUSIONS

These data indicate that progesterone results in an increased leukocyte and T-cell concentration in human endometrium.

MHC Class II positive cells and T cells in the equine endometrium throughout the oestrous cycle

The quantity and distribution of MHC Class II positive cells and T cells in the equine endometrium was investigated throughout the oestrous cycle. Significantly more MHC Class II positive cells were detected in the stratum compactum and stratum spongiosum of endometria from naturally cycling mares during the follicular than during the luteal phase of the oestrous cycle. Significantly more T cells were also detected in the stratum compactum, but not stratum spongiosum, of these mares during the follicular phase. Furthermore, there was a marked increase in the number of MHC Class II positive cells and T cells in the endometria of ovariectomised mares treated with oestradiol compared with progesterone. An increase in the expression of MHC Class II antigen by endometrial epithelial cells was also observed in mares treated with oestradiol and in some naturally cycling mares during the follicular phase.

Immunohistochemical characterization of leucocyte subpopulations in endometriotic lesions

Leucocyte subpopulations localized in endometriotic lesions were analysed using the avidin-biotin immunoperoxidase technique on 15 biopsies obtained by CO2 laser excision. Qualitative assessment of the leucocyte subpopulations was performed with a panel of antihuman monoclonal antibodies for leucocytes (anti-Hle-1), T-lymphocytes (anti-leu-4), T helper/inducer (anti-leu-3a), T suppressor/cytotoxic (anti-leu-2a), B cells (anti-leu-12), HLA-DR (anti-HLA-DR), macrophages (anti-leu-M3) and natural killer cells (anti-leu-7, anti-leu-11; anti-leu-19). Leucocyte common antigen (anti-Hle-1)-positive cells were present in all lesions and were the most frequent stromal leucocytes. Of these, the T lymphocytes are the most frequent subpopulation together with the macrophages. The CD4/CD8 ratio was 0.78. No anti-leu-7 and/or anti-leu-11-positive cells were found although a substantial amount of anti-leu-19-positive cells were found in each lesion. There were very few B cells present in the ectopic endometrial lesions. In conclusion, an important amount of cytotoxic lymphocytes (anti-leu-2a -and anti-leu-19-positive cells) and macrophages (anti-leu-M3) were found in the endometriotic lesions. The possible importance of these intraendometriotic leucocytes for the pathophysiology of endometriosis will be discussed.

Enhanced expression of resident leukocyte interferon gamma mRNA in endometriosis

PROBLEM

Previous studies have shown that the endometrial epithelial/stromal cell proliferative activity of endometriosis is significantly less than that of normal endometrium and that the concentration of resident stromal leukocytes is significantly greater in ectopic than in eutopic endometrium. Other work has shown that interferon gamma (IFN gamma), secreted by resident leukocytes, inhibits endometrial cell proliferation in vitro. Accordingly, we hypothesized that the lower proliferative activity of endometriosis may be related to enhanced resident leukocyte IFN gamma production. This study was designed to assess whether resident leukocytes in endometriosis express IFN gamma mRNA and to compare this expression to that of normal endometrium.

METHODS

Biopsies of ectopic endometrium (N = 16) from women in the follicular phase and normal proliferative (N = 9) and secretory (N = 8) endometria were examined for IFN gamma expression. Using monoclonal antibodies specific for CD45 (leukocyte common antigen), CD3 (a T-cell marker) and CD11c (a macrophage marker), leukocyte types were identified immunocytochemically, followed by in situ hybridization to examine expression of IFN gamma mRNA.

RESULTS

Results demonstrated that (1) the overall concentration of T cells and macrophages expressing IFN gamma mRNA is significantly greater in endometriosis as compared to eutopic endometrium, and (2) the percent of each leukocyte type expressing IFN gamma mRNA is greater in endometriosis than in normal endometrium.

CONCLUSIONS

These findings support a possible paracrine role for resident leukocytes in regulating cell proliferation in endometriosis.

An immunohistological study of MHC class II expression and T lymphocytes in the endometrium of the mare

The distribution of T lymphocytes and of cells bearing MHC Class II antigens in the endometrium of the mare was studied using an avidin-biotin-peroxidase staining method. The cells within the endometrium which expressed MHC Class II were macrophages, lymphocytes, monocytes, dendritic cells, epithelial cells and endothelial cells. MHC Class II expression increased significantly (P < 0.05) in the luminal epithelium and tended (P = 0.0573) to increase in the subepithelial layers during oestrus. Numbers of T lymphocytes did not differ between oestrus and dioestrus. MHC Class II expression and T lymphocyte numbers were not significantly different in samples collected on Day 14 of dioestrus and on Day 14 of pregnancy. The presence of endometritis greatly increased MHC Class II expression and T lymphocyte numbers within the endometrium.

Endometrial lymphoid tissue in the timed endometrial biopsy: morphometric and immunohistochemical aspects

OBJECTIVES

The purpose of this study was to provide a morphometric profile of endometrial granulated lymphocytes and to investigate qualitative and quantitative differences in leukocyte subsets in precisely timed luteal phase endometrial biopsies.

STUDY DESIGN

Endometrial biopsies were obtained from 24 normal fertile women at 4, 7, 10, and 13 days after the luteinizing hormone surge. Endometrial granulated lymphocytes were assessed morphometrically in 2 microns resin sections. Eleven monoclonal antibodies were used to characterize leukocytes in frozen sections. Semiquantitation was performed with a Quantimet 970 image analyzer. Data were analyzed with one-way analysis of variance.

RESULTS

CD8+ (T suppressor-cytotoxic) cells increased significantly from 4 to 7 days after the luteinizing hormone surge, whereas CD68+ macrophages increased from days 10 to 13. Lymphocytes with an unusual phenotype (CD56+, CD38+, CD2+) increased dramatically after 7 days. The volume fraction of endometrium occupied by the nuclei of endometrial granulated lymphocytes did not alter, but their mean nuclear diameter and axial ratio decreased from days 7 to 13.

CONCLUSION

The morphometric findings indicate in situ proliferation of endometrial granulated lymphocytes rather than migration from the peripheral circulation. T lymphocytes, macrophages, and endometrial granulated lymphocytes increase significantly between certain stages of the luteal phase.

The distribution and possible function of gamma interferon-immunoreactive cells in normal endometrium and myometrium

T-lymphocytes are present in normal endometrium, where they may have a role in the control of glandular maturation. T-cell activity could be related to the local secretion of cytokines such as gamma interferon, which has an anti-proliferative effect on endometrial epithelial cells in vitro. We have examined gamma interferon immunoreactivity and T-cell distribution in 24 normal pre-menopausal uteri. Endometrial appearances were representative of all stages of the menstrual cycle. Most cells in the lymphoid aggregates in the stratum basalis were stained by T-cell and gamma interferon antisera. T-lymphocytes were also scattered in glandular epithelium and throughout the stroma of basal and functional layers; immunoreactivity for gamma interferon was less consistent in these cells. There was no alteration in the intensity or distribution of gamma interferon staining in different phases of the menstrual cycle. Endometrial granulocytes (K-cells) present mainly in the late secretory endometria were not reactive with the gamma interferon antiserum. In addition to endometrial staining, T-cells were distributed in all areas of the myometrium in most uteri, and many myometrial lymphocytes were gamma interferon positive. These results support a role for gamma interferon in endometrial physiology, possibly as an inhibitor of epithelial proliferation.

Macrophage- and lymphocyte-subtypes in the endometrium during different phases of the ovarian cycle

The presence of immunocompetetive cells in the endometrium during the proliferative and secretory phase of the ovarian cycle is demonstrated on the light and electron microscopic level using monoclonal antibodies (MoAb). Subtypes of monocytes, macrophages and T-lymphocytes appear during the different phases in variable extent and different localization. Some subpopulations of the monocyte/macrophage system and T-helper lymphocytes increase in number on day 21/22. Our observations indicate that cells with bone marrow origin take part in functional events of the endometrium during the ovarian cycle.

Isolation of maternal mononuclear cells from placentas for use in in vitro functional assays

Interest in immunoregulatory mechanisms within uteroplacental tissues, particularly in malarial infection during pregnancy, prompted us to develop a technique to extract maternal mononuclear cells from human term placentas. This method is described. The phenotypes of isolated cells were characterised for expression of CD45, CD3, CD4, CD8, CD14, CD15, CD68, CD22, CAM 5.2 and class II MHC antigens and compared with those in situ in frozen sections of the same placentas. Isolated mononuclear cell preparations were examined for contamination by fetal trophoblasts. Fetal leukocyte contamination appeared unlikely since histological sections of placental tissue, after the extraction of maternal leukocytes, showed intact chorionic villi with no disruption of fetal stem vessels. This technique produces preparations of maternal placental mononuclear cells which are representative of cells in situ, show minimal fetal cell contamination and are suitable for functional studies.

Distinct subsets of stromal cells confined to unique microenvironments in human endometrium throughout the menstrual cycle

Human endometrial stroma exhibits rather uniform morphology throughout the endometrium. However, predecidualization develops characteristically around vessels and subsequently around glands and under surface epithelium, demonstrating existence of regional differences among stromal cells. Immunoreactivity of stromal cells in endometrial tissues from various phases of the menstrual cycle, as elucidated by employing monoclonal antibodies to cytokeratin, vimentin, very late antigen-1 (VLA-1), Ber-EP4, and HLA-DR, revealed presence of phenotypically distinct subsets of stromal cells confined to unique microenvironments throughout the menstrual cycle. All stromal cells strongly expressed vimentin and weakly expressed cytokeratin. However, Ber-EP4 positive stromal cells were distinctly confined around glands and to the subluminal regions of the surface epithelium. The intervening stromal cells were Ber-EP4 negative. The HLA-DR positive stromal cells were characteristically present in three different locations: around glands and under surface epithelium, around blood vessels and around HLA-DR positive lymphoid cells. From all antigens studied, only expression of VLA-1 in the stromal cells showed a characteristic change throughout the menstrual cycle. Stromal cells in the proliferative and early secretory phases were VLA-1 negative. However, VLA-1 characteristically developed initially in the HLA-DR positive cells around vessels and then in HLA-DR/Ber-EP4 positive cells around glands and under surface epithelium. Eventually, all stromal cells in the upper functionalis expressed VLA-1 in the late secretory phase of the menstrual cycle. These data underscore a heterogeneity in stromal cells not exemplified by their morphology. Also, they provide a basis for understanding the differences that the stroma exhibits in morphologic and functional differentiation throughout the menstrual cycle.

Immunoreactive endometritis

A benign polyclonal lymphoid proliferation of the endometrium which bears morphological resemblance to the malignant lymphoma is found among women with bleeding disturbances. Seven previous cases have so far been reported in the literature. A retrospective examination of 11,648 endometrial specimens revealed 287 examples of chronic endometritis (2.5%) of which 29 displayed lymphoid proliferation. We found no evidence of malignant haematologic disorder after a median observation of 68 months and no positive association with prior or present infectious disease. Histological follow-up of ten patients showed that changes could persist for up to 12 months. We name this benign condition 'immunoreactive endometritis'.

Cytokine regulation of human endometrial function

Human endometrium undergoes sequences of proliferation, and secretion followed by menstruation in a predictable fashion. The importance of systemic factors, steroid hormones, in driving endometrium through these phases is well known. However, it is becoming increasingly apparent that a group of factors collectively called cytokines may also serve a key role as local modulators of endometrial function. Expression of the receptors for cytokines, production of cytokines and the ability to demonstrate modulation of a host of functions of both endometrial epithelium and stroma indicate that human endometrium is uniquely poised to respond to cytokines.

Demonstration and characterization of HLA-DR positive cells in the stroma of human endometrium

The proportion of stromal cells expressing DR antigens of the HLA system or reacting with an anti-macrophage antibody was studied by immunohistochemical methods in human proliferative, secretory and post-menopausal endometria. DR+ cells showed a rounded morphology with short expansions and represented 13-25% of the stromal cells in the proliferative and 16-43% in the secretory endometrium. The cells reacting with the anti-macrophage antibody were similar to DR+ cells, but their number was between 1/2 and 1/10 of DR+ cells. In the post-menopausal endometria no DR+ cells or elements reacting with anti-macrophage antibody were observed. These results suggest that a significant proportion of endometrial stromal cells expressing type II histocompatibility antigens do not belong to the monocyte-phagocyte system and that their number is under hormonal regulation.

The relation between serum sex steroid levels and plasma cell infiltrates in endometritis

We measured serum levels of progesterone and estradiol among 35 patients with endometritis confirmed by endometrial biopsy. The onset of symptoms took place predominantly in the proliferative phase of the cycle. A negative correlation was found between the serum progesterone levels and the histopathologic severity of plasma cell endometritis. Our results suggest that the hormonal status contributes to the immune response and susceptibility to endometrial infection.

Isolation and functional studies of granulated lymphocytes in first trimester human decidua

Granulated lymphoid cells (CD2+, CD7+, CD38+, NKH1+, CD3-, CD5-, CD4-, CD8-, CD25-) are prominent in human endometrial stroma in the late secretory phase of the menstrual cycle and in early pregnancy, and may play an important role in implantation and placentation. Cell suspensions enriched for granulated lymphoid cells were prepared from first trimester human decidua using a panning technique; cells were labelled with the monoclonal antibody NKH1 and separated by adherence to immunoglobulin-coated plates. The enriched cells were characterized with a panel of monoclonal antibodies using an indirect immuno-alkaline phosphatase method, and subjected to various functional assays. Most cells in the enriched preparations showed the characteristic morphology of granulated lymphocytes in smears stained with toluidine blue or May Grunwald Giemsa. CD45+ cells were obtained up to 98 +/- 1% purity (n = 10) and CD2+ cells were enriched up to 84 +/- 4%. The enriched populations were efficient effectors in a K562 chromium-release assay but showed minimal proliferative response to phytohaemagglutinin, concanavalin A, ionomycin and phorbol 12, 13 dibutyrate (PdBU), interleukin 1 or interleukin 2. The precise lineage and in vivo function of decidual granulated lymphocytes remains to be established.

The non-Hodgkin's lymphomas: old and new thinking

Knowledge of non-Hodgkin's lymphomas has increased enormously in the last 10-15 years. The various types are considered to reflect the normal immunological processes that take place in the lymphoid tissue after antigenic challenge. This concept, which states that non-Hodgkin's lymphomas are neoplastic counterparts of normal processes, has implications for morphology, immunology and clinical behaviour. Based on this concept, as well as on immunohistological and functional data, a hypothetical scheme of B-cell development is proposed. The relation to normal physiology also holds for lymphomas localized outside the lymph nodes. Normal structure and function in two important extranodal lymphoid tissues, the gastrointestinal mucosa and the skin-associated lymphoid tissues, are related to the lymphomas arising in these sites. This relation and some of its implications are discussed, with special reference to the important processes of homing and recirculation of lymphocytes.

Immunohistochemical characterization of stromal leucocytes in nonpregnant human endometrium

Stromal leucocytes in normal premenopausal human endometrium were characterised by an indirect immunoperoxidase technique employing a panel of monoclonal antibodies. T cells were scanty in proliferative endometrium but increased in frequency in the secretory phase of the menstrual cycle. An additional population of phenotypically unusual lymphocytes (CD2-positive, CD3-negative) was detected in the stratum functionalis in mid- and late secretory phase endometrium, particularly in areas exhibiting pseudodecidual change. The distribution of these unusual lymphocytes mirrored that of the so-called "endometrial stromal granulocytes," which have recently been shown to be granulated lymphocytes. Macrophages were common throughout the menstrual cycle. B lymphocytes were detected in lymphoid aggregates in the basalis but rarely in the functionalis.

Immunohistologic study of the leukocytic infiltrate in maternal uterine tissues in normal and preeclamptic pregnancies at term

The leukocytic infiltrate in maternal uterine tissues at term in normal and preeclamptic pregnancies was studied immunohistologically using a number of monoclonal antibodies. No differences in the quantity and type of infiltrate are apparent between normal and preeclamptic pregnancy tissues. A large population of macrophages has been identified. Suppressor/cytotoxic T lymphocytes expressing major histocompatibility complex (MHC) class II products but lacking interleukin-2 receptor expression constitute the other component of the bone marrow-derived cell population. The suppressor/cytotoxic cells are seen around both arteries with and without physiologic changes and are seen also in acute atherosis. While it is suggested that the maternal immune response, further functional studies of these leukocytes are required to define their role in normal pregnancy.

The expression of class II MHC gene products by fallopian tube epithelium in pregnancy and throughout the menstrual cycle

The expression of HLA class II antigens by human fallopian tube epithelium was investigated in ectopic tubal pregnancy, in normal early and full-term intrauterine pregnancy, and during the menstrual cycle. Monoclonal antibodies directed against non-polymorphic (DA6.231, CR3/43, B7/21) and polymorphic (DA6.147, DA6.164, anti-leu-10) determinants of the HLA-D locus were used in a standard indirect immunoperoxidase method on fresh cryostat sections of fallopian tube. In ectopic pregnancy the tube epithelium showed uniform, intense reactivity for DR, DP and DQ. A similar reaction pattern was observed in normal first-trimester pregnancy. At term, most epithelial cells were DR-, DP- and DQ-positive, but a few were DP- and DQ-negative. In fallopian tubes from non-pregnant individuals, a variable number of epithelial cells labelled for DR alpha and DR beta but there was essentially no reactivity for DP or DQ. These results suggest differential regulation of class II MHC gene expression by tube epithelial cells, possibly mediated by hormones and/or a trophoblast product.

The immunocytochemical distribution of leukocytic subpopulations in human endometrium

Thirty human endometria were selected from women aged 21-54 years who had undergone routine dilation and curettage procedures for tubal ligation, infertility dating, and irregular menstrual cycling. Histologic sections of the cases chosen were examined to exclude any major pathologic condition (including chronic endometritis). The specimens were stained with monoclonal antibodies to a common leukocytic antigen (H Leu-1 and PD7/26), pan-T-cell antigen (UCHT1), T helper/inducer and T suppressor/cytotoxic antigens (Leu-3a and UCHT4, respectively), pan-B cell antigen (To15 and Leu-12), and macrophage antigens (UCHM1 and Leu-M3). Other antibodies used included TAL-1B5 (anti-HLA-DR), Leu-7 (natural killer cell) and Na 1/34 (anti-T6/Langerhans/interdigitating reticulum cell). The endometria contained significant numbers of common leukocyte antigen-positive cells (occupying approximately 10-15% of the stroma), the numbers of which appeared to increase in the late secretory/pre-menstrual phase (20-25% of the stroma). The major leukocyte populations were T cells and macrophages; the latter, with neutrophils, appeared to account for the premenstrual increase in leukocytes. T cells were distributed both diffusely in the stroma and in periglandular stromal aggregates closely applied to the glands. The T8+ suppressor/cytotoxic population was predominant within the stromal nodules. In addition, scattered intraepithelial T suppressor/cytotoxic cells were present. Macrophages (UCHM1 and HLA-DR+) were also distributed diffusely in the stroma and as part of the periglandular stromal aggregates, in areas sending long cell processes into the epithelium. B cells appeared to be limited to scattered cells in the stroma, only increasing in number within lymphoid follicles. Natural killer cells, as defined by Leu-7+ cells, were also present, scattered singly in the stroma and within lymphoid follicles. The demonstration of large mononuclear dendritic-appearing Na 1/34+ cells within the glands of the endometrium in 5/30 cases suggests the presence of T6+ Langerhans/interdigitating reticulum cells in the endometrium. Thus, the normal endometrium has an important population of immunologically competent cells. Further study of these cell populations may elucidate their contribution, if any, to pathologic conditions in the endometrium.

Induction of HLA-DR antigen expression in human endometrial epithelial cells in vitro by recombinant gamma-interferon

Recent studies suggest that HLA-DR antigens may be inducible in some normal epithelial cells. Therefore, we studied the expression of these molecules in epithelial cell cultures derived from 9 proliferative and 7 secretory endometria with and without treatment by recombinant gamma-interferon (gamma-IFN). A panel of monoclonal antibodies to HLA-DR antigens, T cells, B cells, macrophages, endothelial cells, and cytokeratin was used to stain the cultured cells by the avidin-biotin complex method. The cultures consisted only of epithelial cells as demonstrated by expression of cytokeratin and by electron microscopy and did not contain any T or B cells, macrophages, or endothelial cells. The endometrial epithelial cells were HLA-DR-negative under routine culture conditions but expressed HLA-DR antigens after gamma-IFN treatment in a dose- and time-dependent fashion. The findings indicate that endometrial epithelium can actively synthesize HLA-DR antigens in vitro after induction by gamma-IFN.

Localization of immunoglobulin-containing cells in human endometrium in the first trimester of pregnancy and throughout the menstrual cycle

The distribution of immunoglobulins in normal human endometrium throughout the menstrual cycle and in early pregnancy has been studied with an immunoperoxidase technique. In first-trimester decidua, IgG was detected within many cells of differing morphology and size. Large IgG-containing cells were often binucleate and were believed to be decidual cells. Examination of serial sections showed no kappa or lambda light-chain restriction, suggesting absorption of the immunoglobulin content. Medium-sized, irregular, IgG-containing cells were macrophages. An additional substantial population of small hyperchromatic IgG-containing cells were prominent around arterioles and adjacent to endometrial glands. From examination of adjacent sections stained with phloxine tartrazine, it was concluded that these represented endometrial granulocytes. Labelling for light chains again suggested absorption of the immunoglobulin content. In contrast, in non-pregnant endometrium immunoglobulin-containing stromal cells were uncommon, although IgG and IgA were detected in gland epithelium and secretions and in the stromal interstitium particularly in the secretory phase. These results support the notion that human endometrium lacks a classical secretory immune system and highlight the requirement for correlation between studies of cell surface markers, morphology and cell surface receptors.

The T-lymphocyte population in first-trimester human decidua does not express the interleukin-2 receptor

The expression of the IL-2 receptor by T lymphocytes in human uterine decidua has been studied with two monoclonal antibodies to the IL-2 receptor employed in immunoperoxidase labelling of serial cryostat sections. Infiltrating T lymphocytes in early pregnancy decidua do not express the IL-2 receptor. Endometrial gland epithelium in early pregnancy showed unexpected reactivity with one of the mAbs to the IL-2 receptor (Tac). Thus, despite the close proximity of fetal trophoblast, macrophages and T-lineage lymphocytes in decidua in early pregnancy, IL-2 receptor-bearing lymphocytes are completely absent.

Nature of "basal" and "reserve" cells in oviductal and cervical epithelium in man

The epithelium of the human fallopian tube (oviduct) and cervix were studied by histological, immunohistological, and ultrastructural methods with a view to establishing the nature of the so called "basal" and "reserve" cells. The results indicated that the "basal" cells of the oviductal epithelia were T lymphocytes, with a predominance of T cytotoxic and suppressor cells. A more heterogeneous inflammatory cell population was present in cervical epithelium, although once again T cytotoxic and suppressor cells were the most numerous subtype. The intraepithelial inflammatory cells were quite distinct from the cells commonly referred to as "reserve" cells (reserve cell hyperplasia), which have epithelial characteristics. The origin of the "reserve" cells is unclear, but they seem to arise within the epithelium. They probably represent an early sign of squamous metaplasia. The lymphoid tissue of fallopian tube and endocervix shows similarities with that of the endometrium and mucosal associated lymphoid tissue in general.

Lymphoid tissue and cyclical endometrium

Images