The eosinophilic leukocyte. Fine structure studies of changes in the uterus during the estrous cycle

Spatial adaptation of eosinophils and their emerging roles in homeostasis, infection and disease

Eosinophils are bone marrow-derived granulocytes that are traditionally associated with type 2 immune responses, such as those that occur during parasite infections and allergy. Emerging evidence demonstrates the remarkable functional plasticity of this elusive cell type and its pleiotropic functions in diverse settings. Eosinophils broadly contribute to tissue homeostasis, host defence and immune regulation, predominantly at mucosal sites. The scope of their activities primarily reflects the breadth of their portfolio of secreted mediators, which range from cytotoxic cationic proteins and reactive oxygen species to multiple cytokines, chemokines and lipid mediators. Here, we comprehensively review basic eosinophil biology that is directly related to their activities in homeostasis, protective immunity, regeneration and cancer. We examine how dysregulation of these functions contributes to the physiopathology of a broad range of inflammatory diseases. Furthermore, we discuss recent findings regarding the tissue compartmentalization and adaptation of eosinophils, shedding light on the factors that likely drive their functional diversification within tissues.

Eosinophils as potential biomarkers in respiratory viral infections

Eosinophils are bone marrow-derived granulocytes that, under homeostatic conditions, account for as much as 1-3% of peripheral blood leukocytes. During inflammation, eosinophils can rapidly expand and infiltrate inflamed tissues, guided by cytokines and alarmins (such as IL-33), adhesion molecules and chemokines. Eosinophils play a prominent role in allergic asthma and parasitic infections. Nonetheless, they participate in the immune response against respiratory viruses such as respiratory syncytial virus and influenza. Notably, respiratory viruses are associated with asthma exacerbation. Eosinophils release several molecules endowed with antiviral activity, including cationic proteins, RNases and reactive oxygen and nitrogen species. On the other hand, eosinophils release several cytokines involved in homeostasis maintenance and Th2-related inflammation. In the context of SARS-CoV-2 infection, emerging evidence indicates that eosinophils can represent possible blood-based biomarkers for diagnosis, prognosis, and severity prediction of disease. In particular, eosinopenia seems to be an indicator of severity among patients with COVID-19, whereas an increased eosinophil count is associated with a better prognosis, including a lower incidence of complications and mortality. In the present review, we provide an overview of the role and plasticity of eosinophils focusing on various respiratory viral infections and in the context of viral and allergic disease comorbidities. We will discuss the potential utility of eosinophils as prognostic/predictive immune biomarkers in emerging respiratory viral diseases, particularly COVID-19. Finally, we will revisit some of the relevant methods and tools that have contributed to the advances in the dissection of various eosinophil subsets in different pathological settings for future biomarker definition.

Eosinophilia in cancer and its regulation by sex hormones

Gender differences in the functionality of the immune system have been attributed, in part, to direct and indirect effects of sex steroids, especially estrogens, on immune cell repertoire and activity. Notable are studies that have defined roles for estrogens in the regulation of the biology of dendritic cells (DCs), macrophages, T cells and natural killer (NK) cells. Although estrogens can modulate eosinophil function, the mechanisms by which this occurs and how it contributes to the pathobiology of different diseases remains underexplored. Furthermore, although the importance of eosinophils in infection is well established, it remains unclear as to how these innate immune cells, which are present in different tumors, impact the biology of cancer cells and/or response to therapeutics. The observation that eosinophilia influences the efficacy of immune checkpoint blockers (ICBs) is significant considering the role of estrogens as regulators of eosinophil function and recent studies suggesting that response to ICBs is impacted by gender. Thus, in this review, we consider what is known about the roles of estrogen(s) in regulating tissue eosinophilia/eosinophil function and how this influences the pathobiology of breast cancer (in particular). This information provides the context for a discussion of how estrogens/the estrogen receptor (ER) signaling axis can be targeted in eosinophils and how this would be expected to influence the activity of standard-of-care interventions and contemporary immunotherapy regimens in cancer(s).

Identification of Two Eosinophil Subsets in Induced Sputum from Patients with Allergic Asthma According to CD15 and CD66b Expression

Two subsets of eosinophils have been described: resident eosinophils with homeostatic functions (rEOS) in healthy subjects and in patients with nonallergic eosinophilic asthma, and inflammatory eosinophils (iEOS) in blood and lung samples from patients with allergic asthma. We explored if it would be possible to identify different subsets of eosinophils using flow cytometry and the gating strategy applied to induced sputum. We conducted an observational cross-sectional single-center study of 62 patients with persistent allergic asthma. Inflammatory cells from induced sputum samples were counted by light microscopy and flow cytometry, and cytokine levels in the supernatant were determined. Two subsets of eosinophils were defined that we call E1 (CD66b-high and CD15-high) and E2 (CD66b-low and CD15-low). Of the 62 patients, 24 were eosinophilic, 18 mixed, 10 paucigranulocytic, and 10 neutrophilic. E1 predominated over E2 in the eosinophilic and mixed patients (20.86% vs. 6.27% and 14.42% vs. 4.31%, respectively), while E1 and E2 were similar for neutrophilic and paucigranulocytic patients. E1 correlated with IL-5, fractional exhaled nitric oxide, and blood eosinophils. While eosinophil subsets have been identified for asthma in blood, we have shown that they can also be identified in induced sputum.

Biologicals in atopic disease in pregnancy: An EAACI position paper

Biologicals have transformed the management of severe disease phenotypes in asthma, atopic dermatitis, and chronic spontaneous urticaria. As a result, the number of approved biologicals for the treatment of atopic diseases is continuously increasing. Although atopic diseases are among the most common diseases in the reproductive age, investigations, and information on half-life, pharmacokinetics defining the neonatal Fc receptors (FcRn) and most important safety of biologicals in pregnancy are lacking. Given the complex sequence of immunological events that regulate conception, fetal development, and the intrauterine and postnatal maturation of the immune system, this information is of utmost importance. We conducted a systematic review on biologicals in pregnancy for indications of atopic diseases. Evidence in this field is scarce and mainly reserved to reports on the usage of omalizumab. This lack of evidence demands the establishment of a multidisciplinary approach for the management of pregnant women who receive biologicals and multicenter registries for long-term follow-up, drug trial designs suitable for women in the reproductive age, and better experimental models that represent the human situation. Due to the very long half-life of biologicals, preconception counseling and healthcare provider education are crucial to offer the best care for mother and fetus. This position paper integrates available data on safety of biologicals during pregnancy in atopic diseases via a systematic review with a detailed review on immunological considerations how inhibition of different pathways may impact pregnancy.

The emerging roles of eosinophils in mucosal homeostasis

Eosinophils are granulocytes, typically implicated as end-stage effector cells in type-II immune responses. They are capable of producing a wide array of pre-formed molecules which render them with vast potential to influence a wide variety of processes. Nonetheless, eosinophil research has traditionally focused on their role in anti-helminthic responses and pathophysiological processes in type-II immune disorders, such as allergy and asthma, where eosinophilia is a hallmark phenotype. However, a number of key studies over the past decade have placed this restricted view of eosinophil function into question, presenting additional evidence for eosinophils as critical regulators of various homeostatic processes including immune maintenance, organ development, and tissue regeneration.

Spatio-temporal distribution of eosinophils in the mouse uterus during peri-implantation period

Embryo implantation is an immunologically paradoxical event. In humans and rodents, blastocysts adhere to uterine epithelium and then invade into endometrial stroma, while maternal body is protected from extraneous materials by its immune system. Eosinophils, a kind of leucocytes involving parasitic infections and allergic response, increase in number in uterus when serum estrogen level is elevated during estrus cycles. However, response of uterine eosinophils to ovarian estrogen during peri-implantation period is not clear. Therefore, we investigated the distribution of eosinophils in murine peri-implantation uterus. On day 0.5 of pregnancy, eosinophils were found primarily in endometrial stroma near the luminal epithelium, whereas they were primarily distributed in basal endometrium and myometrium on day 3.5 of pregnancy. The number of uterine eosinophils on day 4.5 of pregnancy was significantly increased by inhibition of maternal estrogen action. Collectively, our results indicate that the ovarian estrogen negatively regulates uterine eosinophil distribution during peri-implantation period and provide insight into a role of maternal immune system in embryo implantation.

Oestrogen amplifies pre-existing atopy-associated Th2 bias in an experimental asthma model

BACKGROUND

The prevalence and severity of asthma, particularly the most common (atopic) form of the disease, increase amongst females but not males after puberty, and asthma activity also changes throughout the menstrual cycle and during pregnancy. The contribution of female sex hormones to asthma pathogenesis is incompletely understood.

OBJECTIVE

To obtain insight into the role of oestrogen (E2) in experimental atopic asthma, and guide future research on sex-related variations in atopic asthma susceptibility/intensity in humans.

METHODS

We utilized an experimental model comprising rat strains expressing dichotomous Th2-high vs Th2-low immunophenotypes exemplified by eosinophilia, mirroring differences between human atopics/non-atopics. We compared the efficiency of Th2-associated immunoinflammatory mechanisms, which differed markedly between the two strains, and between sexes in the Th2-high strain, and determined the effects of E2 administration on these differences.

RESULTS

Unique to the Th2-high strain, eosinophil: neutrophil ratios in the airways at baseline and following sensitization/aeroallergen challenge were logfold higher in females relative to males, and this was reflected by higher baseline blood eosinophil numbers in females. Pretreatment of Th2-high males with E2 abrogated this sex difference by selectively boosting Th2-associated genes in the airways and eosinophilia, but was without corresponding effect in the Th2-low strain. In contrast, parallel E2 effects on myeloid and lymphoid cell populations were relatively modest.

CONCLUSIONS AND CLINICAL RELEVANCE

E2 acts to amplify the eosinophilic component of pre-existing Th2-high immunophenotype, possibly acting at the level of the common eosinophil/neutrophil precursor in bone marrow to preferentially drive eosinophil differentiation. Constitutive granulocyte profiles in which the balance between eosinophils and neutrophils is skewed towards eosinophils have been identified in independent cohort studies as markers of asthma risk, and these findings suggest that more detailed studies on the role of E2 in this context, and in relation to asthma pathogenesis in post-pubertal females in particular, appear warranted.

Homeostatic Eosinophils: Characteristics and Functions

Eosinophils are typically considered to be specialized effector cells that are recruited to the tissues as a result of T helper type 2 (Th2) cell responses associated with helminth infections or allergic diseases such as asthma. Once at the site of injury, eosinophils release their cytotoxic granule proteins as well as preformed cytokines and lipid mediators, contributing to parasite destruction but also to exacerbation of inflammation and tissue damage. Accumulating evidence indicates that, besides their roles in Th2 responses, eosinophils also regulate homeostatic processes at steady state, thereby challenging the exclusive paradigm of the eosinophil as a destructive and inflammatory cell. Indeed, under baseline conditions, eosinophils rapidly leave the bloodstream to enter tissues, mainly the gastrointestinal tract, lungs, adipose tissue, thymus, uterus, and mammary glands, where they regulate a variety of important biological functions, such as immunoregulation, control of glucose homeostasis, protection against obesity, regulation of mammary gland development, and preparation of the uterus for pregnancy. This article provides an overview of the characteristics and functions of these homeostatic eosinophils.

Multi-parameter flow cytometric analysis of uterine immune cell fluctuations over the murine estrous cycle

Investigating immune cell populations within various reproductive tissues commonly utilises flow cytometric methods. With advances in fluorophore technology and equipment capabilities, multiple cell types from a single tissue sample can be identified by using different combinations of cell surface markers to distinguish specific cell populations. Here a protocol optimized for mouse uterine tissue was used to show the proportional changes in dendritic cells, monocyte/macrophages, T and B cells, NK and NK T cells, and the granulocytes, neutrophils and eosinophils at each of the four stages of the estrous cycle. Importantly, we demonstrate that use of anti-SiglecF or assessment of FSC/SSC plots could be used to differentiate monocyte/macrophage and eosinophil populations that otherwise cannot be distinguished by use of the common combination of antibodies against F4/80 and CD11b. Our results clearly indicate that within the uterus a dynamic population of immune cells resides, with many cell types reaching peak abundance at estrus and metestrus phases of the cycle, consistent with their importance in the response to paternal antigens and/or pathogens encountered after insemination.

Estrogen Signaling Modulates Allergic Inflammation and Contributes to Sex Differences in Asthma

Asthma is a chronic airway inflammatory disease that affects ~300 million people worldwide. It is characterized by airway constriction that leads to wheezing, coughing, and shortness of breath. The most common treatments are corticosteroids and β2-adrenergic receptor antagonists, which target inflammation and airway smooth muscle constriction, respectively. The incidence and severity of asthma is greater in women than in men, and women are more prone to develop corticosteroid-resistant or “hard-to-treat” asthma. Puberty, menstruation, pregnancy, menopause, and oral contraceptives are known to contribute to disease outcome in women, suggesting a role for estrogen and other hormones impacting allergic inflammation. Currently, the mechanisms underlying these sex differences are poorly understood, although the effect of sex hormones, such as estrogen, on allergic inflammation is gaining interest. Asthma presents as a heterogeneous disease. In typical Th2-type allergic asthma, interleukin (IL)-4 and IL-13 predominate, driving IgE production and recruitment of eosinophils into the lungs. Chronic Th2-inflammation in the lung results in structural changes and activation of multiple immune cell types, leading to a deterioration of lung function over time. Most immune cells express estrogen receptors (ERα, ERβ, or the membrane-bound G-protein-coupled ER) to varying degrees and can respond to the hormone. Together these receptors have demonstrated the capacity to regulate a spectrum of immune functions, including adhesion, migration, survival, wound healing, and antibody and cytokine production. This review will cover the current understanding of estrogen signaling in allergic inflammation and discuss how this signaling may contribute to sex differences in asthma and allergy.

Leukocyte population dynamics and detection of IL-9 as a major cytokine at the mouse fetal-maternal interface

Despite much interest in the mechanisms regulating fetal-maternal interactions, information on leukocyte populations and major cytokines present in uterus and placenta remains fragmentary. This report presents a detailed and quantitative study of leukocyte populations at the mouse fetal-maternal interface, including a comparison between pregnancies from syngeneic and allogeneic crosses. Our results provide evidence for drastic differences not only in the composition of leukocyte populations in the uterus during pregnancy, but also between uterine and placental tissues. Interestingly, we have observed a significant decrease in the number of myeloid Gr1+ cells including monocytes, and myeloid CD11c+ cells including DCs in placenta from an allogeneic pregnancy. In addition, we have compared the expression levels of a panel of cytokines in non-pregnant (NP) or pregnant mouse uterus, in placenta, or in their isolated resident leukocytes. Qualitative and quantitative differences have emerged between NP, pregnant uterus and placenta. Unexpectedly, IL-9 was the major cytokine in NP uterus, and was maintained at high levels during pregnancy both in uterus and placenta. Moreover, we have found that pregnancy is associated with an increase in uterine IL-1a and a significant decrease in uterine G-CSF and GM-CSF. Comparing allogeneic versus syngeneic pregnancy, less allogeneic placental pro-inflammatory cytokines CCL2 (MCP-1), CXCL10 (IP-10) and more IL1-α in whole uterus was reproducibly observed. To our knowledge, this is the first report showing a detailed overview of the leukocyte and cytokine repertoire in the uterus of virgin females and at the fetal-maternal interface, including a comparison between syngeneic and allogeneic pregnancy. This is also the first evidence for the presence of IL-9 in NP uterus and at the maternal-fetal interface, suggesting a major role in the regulation of local inflammatory or immune responses potentially detrimental to the conceptus.

Spermatozoa and seminal plasma induce a greater inflammatory response in the ovine uterus at oestrus than dioestrus

Leukocyte infiltration and increased synthesis of cytokines in response to insemination is considered to enhance reproductive success. The present study investigated the inflammatory response to whole semen, spermatozoa and seminal plasma, with and without the addition of antibiotics, in the ovine uterus at oestrus and dioestrus. Seminal plasma and spermatozoa both contributed to increased IL-8 secretion (P < 0.01) by endometrial epithelial cells and a concurrent infiltration by neutrophils (P < 0.01). Increased GM-CSF secretion (P < 0.01) occurred in response to whole semen and spermatozoa when antibiotics were not used. Macrophages and eosinophils increased (P < 0.05) in the endometrial stroma when antibiotics were not used, and fewer mast cells were detected in the deep endometrial stroma after treatments containing antibiotics (P < 0.05). Neutrophil and IL-8 responses to insemination were greater at oestrus (P < 0.01) than at dioestrus and the GM-CSF response followed a similar trend. Eosinophil numbers were increased at oestrus (P < 0.01) but minimally affected by insemination. More macrophages were located in the superficial endometrial stroma at oestrus. These results indicate that spermatozoa, seminal plasma and possibly bacteria contribute to the post-insemination inflammatory response, and that leukocytes, GM-CSF and IL-8 secretion in the ovine uterus are influenced by ovarian hormones.

Indirect evaluation of estrogenic activity post heterotopic ovarian autograft in rats

PURPOSE

To morphologically evaluate the estrogenic effect on the uterus and vagina of rats submitted to ovarian autografts.

METHODS

Twenty Wistar EPM-1 adult rats were bilaterally ovariectomized, followed by ovarian transplants in retroperitoneal regions. The animals were divided in four groups of five animals, according to the day of euthanasia: G4, G7, G14 and G21, corresponding to the 4th, 7th, 14th and 21st day after surgery, respectively. Vaginal smears were collected from the first day of surgery until euthanasia day. After that, the vagina and uterus were removed, fixed in 10% formaldehyde and submitted to histological analysis and stained with hematoxiline and eosine.

RESULTS

All animals showed estrous cycle changes during the experiment. In 4th day, the uterus showed low action of estrogen with small number of mitosis and eosinophils as well as poor development. On the 7th day, the endometrium was atrophic without mitotic signals and presented a small number of eosinophils. On the 14th and 21th days the histological findings were similar, with the presence of mitosis in the endometrial glands and intense leucocyte infiltration with a large number of eosinophils. Morphometric results showed that the endometrial and myometrial thickness as well as the number of eosinophils presented the highest values during the 14th and 21th days of the evaluation. The 7th day group also presented the lowest eosinophil numbers. Vaginal epithelium features were: 4th and 7th day groups presented non-keratinized stratified epithelium with 5 and 2 cell layers, respectively. The 14th and 21st day groups presented non-keratinized stratified epithelium with 14 and 15 cell layers.

CONCLUSION

Experimental ovarian autografts in the evaluated organs presented maximum estrogen activity after the 21st day of surgery, according to morphological and morphometric data.

Presence of the P2X(7) purinergic receptor on immune cells that invade the rat endometrium during oestrus

Eosinophils, macrophages and other leucocytes invade the uterine endometrium during oestrus and play a role in the tissue remodeling and immune responses that occur prior to implantation of the fertilized ovum. Adenosine 5'-triphosphate (ATP) and its metabolites influence uterine function via ATP receptors. In this study, we investigated the presence and localisation of the P2X(7) nucleotide receptor in the cells that infiltrate the uterine endometrium of adult female rats during oestrus at the electron microscope level, using gold-silver pre-embedding immunocytochemical techniques. P2X(7) receptor expression was found in the cytoplasm and the cell membrane of eosinophils, macrophages and fibroblasts in the endometrium during oestrus. These results suggest that ATP-mediated responses may be important in uterine preparation and remodeling before implantation and that this may involve several types of cells. In particular, the presence of P2X(7) receptors on endometrial stromal cells may indicate their involvement in apoptosis and immune and inflammatory responses.

Interleukin-5 transgene expression and eosinophilia are associated with retarded mammary gland development in mice

Eosinophils are prevalent in the female reproductive tract, where they may contribute to regulation of development and maintenance of epithelial integrity. The present study examined the effects of constitutive interleukin-5 (IL-5) expression and overabundance of eosinophils on the development and function of the mammary gland, uterus, and ovary in mice. Eosinophils were up to 13-fold and 4-fold more abundant in the uterus and mammary gland, respectively, in female IL-5 transgenic (IL-5Tg) mice than in wild-type (Wt) animals. Eosinophils were present in large numbers in regressing corpora lutea in IL-5Tg mice but not in ovaries from Wt mice. Postpubertal mammary gland development was retarded in IL-5Tg mice, with impaired terminal end bud formation and an altered pattern of epithelial cell proliferation across the mammary fat pad coincident with disrupted ductal branching and extension. By 10 wk of age, the ductal tree was complete in both genotypes. Onset of first estrus was also delayed in IL-5Tg mice, but once IL-5Tg mice reached puberty, serum estrogen content across the cycle and estrous cycle duration were normal. The histology of uterine tissue and epithelial cell turnover were unchanged. Capacity to mate and achieve pregnancy was not affected by maternal IL-5 transgene expression, although at Day 18 of gestation, a modest decrease in the fetal:placental weight ratio was observed. Furthermore, parturition and ability to lactate and nurture postnatal pup development were not compromised. These data demonstrate an effect of IL-5 overexpression on ductal morphogenesis during postpubertal mammary gland development that is consistent with a direct regulatory role for eosinophils in these events, but these data also show that eosinophil excess does not have long-term consequences for adult reproductive function.

A simple method for the in situ detection of eosinophils

A simple and rapid method for identifying eosinophils in tissue sections is described. The assay is based on the incubation of frozen tissue sections with phenol red and the detection of cellular fluorescence. A one-to-one relationship was observed between cells exhibiting fluorescence following exposure to phenol red and eosinophils as identified by histochemical detection of eosinophil peroxidase (EPO) activity. Using the phenol red assay, eosinophils were detected in various eosinophil-infiltrated tissues, including uteri of rats from day 1 of pregnancy and uteri of prepubertal estrogen-treated rats. Intensity of the fluorescing eosinophils was dependent upon phenol red concentration and duration of incubation. The phenol red method of eosinophil identification was disrupted by co-incubation with resorcinol, an EPO inhibitor, or catalase, a hydrogen peroxide scavenger. The merits of this assay are its simplicity and compatibility with other procedures, such as histochemistry, immunocytochemistry, and in situ ligand-receptor binding.

Eotaxin is required for eosinophil homing into the stroma of the pubertal and cycling uterus

The presence of eosinophils in the endometrium of rodents during the estrous cycle or after E2 administration to ovariectomized animals is well documented. Nevertheless, the chemoattractant for eosinophils and the function of E-dependent eosinophils during the estrous cycle remain unknown. Using mice homozygous for a null mutation in the gene for eotaxin, a specific chemokine for eosinophils, we have identified eotaxin as being necessary for eosinophil homing into the uterine stroma, and regulated by E2 during the estrous cycle. In the absence of eosinophils, the onset of estrous cycle displayed a 2-wk delay along with the first age of parturition, suggesting a possible local role of eosinophils present in the pubertal uterus in preparing the mature uterus for pregnancy. However, despite the absence of eosinophils, once the mice reach maturity, their estrous cycles as well as their reproductive functions were normal. Our results demonstrate that E2 acts through eotaxin to recruit eosinophils to the uterine stroma during the estrous cycle in mice, but that these cells do not have a function in regulating either the duration of the estrous cycle or fertility of mice.

Fibroblasts and eosinophils in normal fibroplasia of ferret vulval skin, shown by light and electron microscopy; with special reference to eosinophil degranulation

In order to compare aspects of normal fibroplasia with reports for pathologically fibrotic tissue, light and electron microscopic observations were made on ferret vulval skin, which proliferates markedly with the onset of estrus and regresses equally fast after mating. Estrous tissue, which contained hypertrophied fibroblasts, new collagen, elastic fibers and ground substance, was invaded by numerous eosinophils with extensive release of granules. Eosinophil degranulation was both extra- and intracellular; some cells, completely disintegrated, had released all contents into the extracellular matrix. Extruded granules reacted positively for major basic protein. In regression, diminished fibroblasts incorporated collagen fibrils. Many of the features seen in this normal fibroplasia in ferret vulval skin are similar to those in pathologic situations. Thus, in particular, the presence of degranulating eosinophils in pathologic fibrosis does not necessarily indicate that they are the cause of the disease. Our information and that from other sources implies a role for eosinophils in connective tissue change.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) targets myeloid leukocytes in the uterus during the post-mating inflammatory response in mice

Factors in seminal plasma elicit a surge of GM-CSF expression in uterine epithelial cells after mating in mice. This study investigates the nature of the endometrial cell populations targeted by epithelial GM-CSF. In quantitative RT-PCR studies, expression of the alpha-subunit of the GM-CSF receptor (GM-CSF-R) parallelled GM-CSF expression, being maximal during the 48 h period after mating and declining thereafter. Expression of mRNA encoding beta-common chain (AIC2B) also increased after mating and remained high until the time of embryo implantation on day 4 of pregnancy. Cells expressing GM-CSF receptors were identified in sections of uterus on the day after mating using 125I-GM-CSF, and were located predominantly in the endometrial stroma subjacent to the luminal epithelium, co-localising with abundant populations of myeloid leukocytes. Cells expressing GM-CSF receptor were identified as macrophages, granulocytes and putative dendritic cells by flow cytometric analysis using lineage and receptor subunit specific antibodies. Recombinant GM-CSF injected into the uterine lumen of ovariectomised mice was found to elicit a dose-dependant accumulation of macrophages and granulocytes in the endometrium, in a pattern of distribution comparable to that seen in uteri after natural mating. Together, these data indicate a role for epithelial cell-derived GM-CSF in mediating the recruitment and potentially in modifying the behaviour of uterine leukocytes during the post-mating inflammatory response in mice.

Eosinophil accumulation in rat uterus following estradiol administration is modulated by laminin and its integrin receptors

Eosinophils accumulate into the uterus of ovariectomized rats, after treatment with estradiol (E2). We have investigated whether this feature is related to interactions of eosinophils with uterine extracellular matrix proteins: laminin (LM) and fibronectin (FN). Eosinophils isolated from the peritoneal cavity of ovariectomized rats displayed estrogen receptors measured at both binding activity and mRNA levels. An increased number of laminin binding sites, calculated by Scatchard analysis using iodinated LM was determined in E2-treated eosinophils (70,100 +/- 28,000 sites/cell vs 21,000 +/- 5,000 sites/cell in controls). Eo binding to 125I-LM- was inhibited by the E8-LM fragment. Estradiol up-regulated the expression in eosinophils of alpha 6 and beta 2 integrin subunits evaluated by flow-cytometry as well as by alpha 6 mRNA expression. After E2 treatment, eosinophils showed higher adhesiveness to LM-coated dishes (10 +/- 2 vs 56 +/- 3%) which was inhibited by monoclonal antibodies against alpha 6, beta 1 and beta 2 integrins and by the steroid antagonist tamoxifen. These monoclonal antibodies also blocked the attachment of stimulated eosinophils to uterine cryostat sections obtained from spayed rats previously treated with estradiol. We did not detect any apparent influence of E2 on basal eosinophil adherence or binding to FN although alpha 4 and alpha 5 integrin subunits were expressed in eosinophils. Expression of laminin and merosin in the uterus was determined immunohistochemically. Our results suggest that integrin-laminin interactions may contribute to the preferential eosinophil recruitment in vivo.

Is asthma an endocrine disease?

The prevalence of pediatric asthma has increased in many parts of the world. This increase started more than 30 years ago and is particularly obvious in studies which document the onset of asthma in native populations when they change to a "Western" lifestyle. Besides a genetic influence, numerous environmental factors have been described for the development of asthma. Genetic factors are unlikely to explain the sharp increase within the short time period and also allergen and pollution exposure or any specific infection does not actually seem to be the main cause for this phenomenon. Another factor, however, that fits well into the geographical and temporal background of the asthma epidemic is the mother's oral contraceptive use. We therefore review the epidemiological association with later asthma in the children, give a summary of estrogen effects on immune function and develop a preliminary theory how oral contraception could influence later pregnancy.

Eosinophil lysis and free granules: an in vivo paradigm for cell activation and drug development

Release of cytotoxic granule proteins from activated eosinophil granules is considered to be a key pathogenic mechanism in eosinophilic diseases. Degenerated eosinophils and extracellular eosinophil granules have been repeatedly depicted. The present overview describes evidence that eosinophil lysis and distribution of free eosinophil granules (as opposed to 'classical degranulation') is an important mechanism by which eosinophils affect their surroundings. Here, Carl Persson and Jonas Erjefält summarize how recent reports on the induction of eosinophil lysis in vivo provide a new paradigm for eosinophil activation and thus constitute a novel basis for pharmacological manipulations in eosinophilic diseases.

Increased eosinophil granule proteins in gut lavage fluid from patients with inflammatory bowel disease

OBJECTIVE

To explore the potential role of eosinophils in the pathogenesis of inflammatory bowel disease (IBD).

DESIGN

We measured the concentrations of eosinophil granule proteins-namely, major basic protein, eosinophil peroxidase, eosinophil cationic protein, and eosinophil-derived neurotoxin-in gut lavage fluid.

MATERIAL AND METHODS

Ten healthy persons and 17 patients with IBD (9 with Crohn's disease and 8 with ulcerative colitis) underwent gut lavage. Each study subject submitted an early specimen when lavage effluent became liquid and a late specimen when the output became clear. The concentrations of the granule proteins were measured by immunoassay.

RESULTS

The median concentrations of eosinophil-derived neurotoxin and eosinophil cationic protein were significantly higher in patients with IBD than in control subjects for both early and late lavage specimens. Excretion of eosinophil peroxidase was also significantly higher in patients with IBD than in the healthy control subjects, but only in the early specimens. No differences were noted in the concentrations of any of the proteins between patients with ulcerative colitis and those with Crohn's disease.

CONCLUSION

Concentrations of eosinophil granule proteins were increased in whole gut lavage fluid from patients with IBD in comparison with healthy control subjects. These results encourage further studies of the role of eosinophils in the pathogenesis of IBD.

Immunohistochemical localization of the eosinophil major basic protein in the uterus horn and cervix of the rat at term and after parturition

Distribution of the eosinophil major basic protein (MBP) was studied in the rat uterus horn and cervix by means of immunohistochemistry using an antiserum raised against rat MBP. Various hormonal contexts were investigated: pre- and post-parturition, the estrous cycle, and ovariectomy followed by hormonal treatment or without treatment. MBP was detectable in the cervix as early as 12 h post-partum, appearing in the stroma close to the myometrium. The MBP had spread throughout the stroma toward the luminal epithelium after a few days. In contrast, no MBP was seen in sections of the corresponding pre- and post-partum uteri and in the pre-partum cervix. In cycling rats, MBP was distributed equally in the cervix and uterus and was more abundant during proestrus and estrus. In ovariectomized rats subsequently treated with progesterone, no MBP was detected in the cervix or uterus. In the cervix of ovariectomized rats treated with estradiol, MBP first appeared in the muscle layer situated between the two cervical lumina and then reached the stroma; within a few days only the stroma was stained. Inversely, in the uterus MBP-staining first appeared in the stroma. In conclusion, analysis of the distribution of MBP in rat uterus revealed a marked difference in the response of the cervix and horn to a hormonal environment.

Tissue distribution of constitutive and induced soluble peroxidase in rat. Purification and characterization from lacrimal gland

A thorough search for a soluble peroxidase in 31 different tissues of rat indicated the presence of a constitutive activity only in lacrimal, preputial and submaxillary gland. An induced soluble peroxidase activity was also detected in the lactating mammary gland and in the estrogen-induced uterine secretory fluid. The lacrimal gland was the richest source of the enzyme. No peroxidase activity was detected in the lactating mammary gland of mouse and hamster nor in the preputial gland of mouse and uterine fluid of hamster. The three constitutive and two induced soluble peroxidases of rat had a native molecular mass of 73 kDa by gel filtration and they showed a similar mobility in native PAGE. Lactoperoxidase of cow's milk and solubilized rat membrane-bound peroxidases of uterus, intestine and bone marrow showed in native PAGE a mobility which was distinctly different from that of rat soluble peroxidases. As the lacrimal gland of rat was the richest source of soluble peroxidase, the enzyme was purified from this gland to apparent homogeneity; SDS/PAGE then showed a single band of molecular mass 75 kDa which was similar to that obtained by gel filtration. Peroxidase also purified from preputial and submaxillary gland, as well as commercial lactoperoxidase, had a similar molecular mass on SDS/PAGE to purified lacrimal peroxidase. The visible spectrum of lacrimal peroxidase was similar to that of lactoperoxidase but different from membrane-bound peroxidase of rat neutrophils. On isoelectric focussing, purified lacrimal peroxidase resolved into about 14 multiple forms spanning a pI range of 6.5-3.5 while lactoperoxidase focussed at the cathode. Evidence presented suggests that the multiple forms are possibly due to differences in glycosylation. Immunodiffusion, immunoprecipitation and Western blot using antilacrimal peroxidase serum showed a similar interacting species for all five soluble peroxidases of rat while membrane-bound peroxidases showed no interaction. Although in immunodiffusion, the antiserum failed to cross-react with lactoperoxidase it did interact with lactoperoxidase on Western blot. The results indicate that the various constitutive and induced soluble peroxidases of rat tissues are similar to lacrimal peroxidase but are distinctly different from the known membrane-bound peroxidases of rat. However the lacrimal peroxidase shows both similarities as well as dissimilarities with bovine lactoperoxidase. This soluble peroxidase system of rat could be useful to study tissue-specific regulation of gene expression at the molecular level.

Complement C3 synthesis, peroxidase activity and eosinophil chemotaxis in the rat uterus: effect of estradiol and testosterone

Treatment of immature rats with estradiol (E2) produced a large increase in uterine peroxidase activity which was accompanied by an increase in eosinophil chemotactic factor (ECF-U). The synthesis of complement C3 was also induced in the uterus and the amount of this 180 kDa protein was determined both by immunoprecipitation and after separation by polyacrylamide gel electrophoresis. Testosterone (T) did not produce an increase in any of these parameters although it antagonized the estrogen-induced increase in uterine peroxidase activity and these effects were more pronounced in estrogen-primed animals. This antagonism was prevented by the antiandrogen, flutamide. Testosterone showed little effect on eosinophil chemotactic activity and did not inhibit the E2-stimulated synthesis of C3. The results with T were supported by the lack of any significant effect by flutamide which antagonizes receptor-mediated androgenic events. These findings are discussed in relation to the action of other types of hormonal steroids (progesterone, dexamethasone) in inhibiting these estrogen-induced molecular changes in the rat uterus and contribute to our understanding of steroid-steroid interaction and the regulation of uterine function.

Investigations concerning the relationship of ovarian eosinophilia to ovulation and luteal function in the sheep

Eosinophilic leukocytes are attracted into the preovulatory follicle and regressing corpus luteum of sheep. Eosinophils produce a wide array of potent bioactive substances that could play a role in ovarian function. Circulatory eosinophils were depleted by treatment of ewes with prednisolone, thereby producing ovarian eosinopenia. Ovulation occurred in these animals. However, circulatory concentrations of progesterone during the ensuing luteal phase were less than normal. This insufficiency was attributed in part to a suppressed angiogenic response in the formative corpus luteum. Regression of the corpus luteum induced by prostaglandin F2 alpha was not affected by administration of prednisolone. Thus, an obligatory role of eosinophils in the mechanics of ovulation and luteal regression in the sheep is unlikely.

Identification and tissue localization of an eosinophil 17 kDa protein accumulating in rat uterus upon estradiol treatment

In a previous paper (J. Steroid Biochem. 29 (1988) 475-480), the isolation of a 17 kDa protein that was dramatically induced in the uterus of estrogen-treated spayed rats was presented. We now describe a new purification procedure that is compatible with microsequencing of the 17 kDa protein. The protein partial N-terminal amino acid sequence analysis gave 28 residues that revealed a strong homology to the human major basic protein (MBP) of eosinophils described by Wasmoen et al. (J. Biol. Chem. 263 (1988) 12559-12563). Polyclonal rabbit antibodies were raised against this protein and used for tissue or blood cell analysis after electrophoresis and Western blotting. The 17 kDa protein was found to be constitutively present in the stomach and small intestine of the rat and guinea-pig. Estrogen treatment had a clearcut effect in guinea-pig uterus, but not as drastic as that observed in rat uterus. The protein was abundant in purified rat eosinophils. The antibodies cross-reacted with human MBP and an equivalent molecular weight human polymorphonuclear leukocyte protein. Immunohistochemical staining of rat uterus sections showed that the protein was first only associated with eosinophils that emigrate upon estrogen treatment; it then spread throughout the stroma and the deep glandular epithelium. It was not found in the myometrium. In conclusion, the appearance of a 17 kDa protein that is presumably the rat MBP is clearly regulated in the rat uterus.

Progesterone promotes a massive infiltration of the rat uterine cervix by the eosinophilic polymorphonuclear leukocytes

Rat uterine cervices contained an eosinophilic infiltrate during labor, whereas samples of cervices obtained from nonpregnant controls had no infiltrate. A heavy eosinophilic invasion, which closely resembled that of the cervix uteri at term, could be reproduced in ovariectomized rats following progesterone administration, but not in spayed rats injected with estrogen. Light and electron microscopic evidence showing a widespread collagenolysis in the cervical stroma at term is presented. This collagenolysis follows the eosinophilic invasion. On the basis of these observations, a possible role for the eosinophilic infiltrate of the uterine cervix is discussed.

Effect of estrophilic platinum complex on the mouse uterus

Resistance of hormone-dependent mammary carcinoma to cisplatin as a potent antitumor agent led to the synthesis of other estrophilic platinum complexes. In this investigation, the effects of a newly synthesized estrogen-receptor affine platinum complex on the mouse uterus were studied using light and electron-microscopy. The results have been compared with Tamoxifen, cisplatin and the estrophilic ligand. Both estrophilic ligand and estrophilic platinum complex produced strong estrogenic effects as well as features characteristic of the uterine epithelial cell in the luteal phase of the cycle, corresponding to a massive stimulation of the surface and glandular epithelial cells. The uteri showed large glandular lumina. An increase in the number of multivesicular and residual bodies, accompanied by a proliferation of eosinophilic granulocytes, was also seen. The appearance of inter- and intracellular lumina and the activation of smooth muscle cells represent further characteristic effects of the estrophilic ligand and estrophilic platinum complex. Anticipated increases in the incidence of cell death and/or deviant cyto-nuclear architecture in the uteri treated with cisplatin or platinum complex, were not observed.

Leucocyte surface antigens in metrial gland tissue of ovariectomized pregnant rats, deciduomata-bearing rats and in uterine tissue of non-pregnant rats

The effects of withdrawal of ovarian hormones and absence of paternal antigens on numbers and distribution of cells expressing Ia, Thy 1.1 or leucocyte-common (LC) antigens in the rat metrial gland have been assessed. The distribution of these markers in non-pregnant uterus at various stages of the oestrous cycle has also been investigated. In primigravid rats at Day 15 of gestation, following ovariectomy on Day 12, marker distribution was not different from that in uninterrupted pregnancy. However, there was a significant increase in the percentage of cells expressing LC antigen, which was not accompanied by an increase in the percentage of the glycoprotein-containing, LC antigen-positive granulated metrial gland (GMG) cells. It was suggested that the accumulation of LC antigen-positive, non-GMG cells might represent the precursors of GMG cells. In deciduomata-bearing rats, there was a significantly lower percentage of LC antigen-bearing cells at Day 13 of pseudopregnancy than in pregnant rats at Day 13, but no difference in the percentages of GMG cells was noted. Cells expressing Ia, LC or Thy 1.1 antigens were detected in the endometrial stroma, surrounding endometrial glands and the luminal epithelium of the non-pregnant uterus.

The eosinophilic leukocyte: structure and function

The evidence reviewed here indicates that the eosinophil has the ability to kill many species of helminths and likely does so during worm infection. This toxic ability appears to be regulated by several other cells including mast cells, monocytes, and T lymphocytes. Eosinophils kill helminths through their ability to generate potent oxidants and through their content of cationic proteins, which likely achieve high concentrations at points of granule deposition. Eosinophils also participate in inflammation in human disease especially asthma, skin diseases, and heart disease. Though present concepts hold that the mast cell is the cornerstone of the allergic inflammatory response (450), the findings that eosinophils bind IgE and are activated by antigen-IgE complexes and that the eosinophil can elaborate many inflammatory mediators raise the possibility that the eosinophil might also be involved in the initiation of inflammatory responses. Finally, an eosinophil-related protein appears to play an undefined role in human reproduction.

Rat uterine tissue and cell responses to the presence of plain and indomethacin-delivering IUDs

Plain silastic intrauterine devices or those containing 270 micrograms of indomethacin were inserted into the caudal portion of one uterine horn of mature Wistar rats. After a 3-week period animals were fixed by perfusion on the morning of day 2 after estrus. Segments of uterine tissue corresponding to regions adjacent to and cranial to the devices as well as an equivalent portion of the contralateral horn were embedded in glycol methacrylate. A group of control animals without any form of device were treated in an identical manner. Sections cut from these segments were evaluated by grid-point stereology to ascertain changes in tissue volumes and cell populations. It was found that the presence of plain devices induced hypertrophy in the stroma and myometrium of the portion of the uterus adjacent to the device. The presence of indomethacin in such devices prevented stromal hypertrophy. No changes in populations of fibroblasts or areas of glandular or vascular tissue were evident in any treatment group. Cell populations of neutrophils, eosinophils, and mononuclear cells, however, were elevated in the superficial stroma of the horns bearing either type of device; this feature was more pronounced for neutrophils in the presence of the indomethacin devices. Neutrophils, rather than eosinophils, predominated in the epithelia of the uterus bearing either type of IUD. Conversely, eosinophil populations were reduced in the superficial tissues cranial to the devices delivering indomethacin. Neutrophils and mononuclear cells were also found to be elevated in the deep stroma of tissues adjacent to both the plain and medicated device.

Elevated serum levels in human pregnancy of a molecule immunochemically similar to eosinophil granule major basic protein

We have shown that serum levels of a molecule immunochemically similar to eosinophil granule major basic protein (MBP) are elevated in pregnant women throughout gestation. MBP levels increase during gestation and plateau at approximately 7,500 ng/ml by the 20th wk (greater than 10-fold above normal). Levels return to normal after delivery, with a T1/2 of 13.7 d. The MBP in pregnancy serum is remarkably similar to the eosinophil granule MBP in that: (a) pregnancy MBP fully inhibits the binding of radiolabeled MBP standard in a double antibody radioimmunoassay; (b) this inhibition reaction is specific for human MBP because pregnancy serum produces no inhibition of the binding of radiolabeled guinea pig MBP in the guinea pig MBP radioimmunoassay; (c) in a two-site immunoradiometric assay for MBP, slopes of dose-response curves for pregnancy serum, purified MBP, and serum from a patient with hypereosinophilic syndrome are identical, and maximal binding is comparable; (d) reduction and alkylation of pregnancy sera increases measured MBP 100-fold, as previously shown for eosinophil granule MBP in serum; and (e) the MBP in pregnancy serum demonstrates the same pattern of heat lability as has been previously reported for MBP. Four observations have raised the possibility that the eosinophil is not the source of the MBP in pregnancy serum: (a) no correlation between serum MBP level and peripheral blood eosinophil count exists in pregnant women, in contrast to previous studies of patients with eosinophilia; (b) levels of three other eosinophil-associated proteins are normal or low in pregnancy sera, whereas the serum levels of these proteins are elevated in patients with eosinophilia; (c) the slopes of dose-response curves for pregnancy sera and MBP standards differ in the double antibody radioimmunoassay; and (d) the molecule in pregnancy serum elutes from Sephadex G-50 columns at the void volume, while eosinophil granule MBP and the MBP in serum of patients with eosinophilia elute at a volume consistent with the previously established molecular weight of 9,300. These findings suggest that the MBP in pregnancy serum is derived from a source other than the eosinophil.

Oxygen-dependent microbicidal systems of phagocytes and host defense against intracellular protozoa

The role of oxygen-dependent microbicidal systems of leukocytes in the host defense against the major nonerythrocytic intracellular protozoa which infect man--Toxoplasma gondii, Trypanosoma cruzi, and the Leishmania species--is reviewed. The hydrogen peroxide-halide-peroxidase microbicidal system is uniformly cidal to these organisms in vitro. Peroxidase-independent oxygen product(s) toxicity is more variable. Studies to data indicate that phagocytes which contain granule peroxidase and which have the capacity to generate a vigorous respiratory burst; eg, neutrophils and monocytes, possess substantial activity against these protozoa. The absence of granule peroxidase together with the markedly attenuated respiratory burst of resident macrophages leaves these cells with a severe microbicidal defect. These protozoa can enter resident macrophages in the absence of antibody and survive and replicate within the intracellular environment. Enhancement of the antiparasite activity of resident macrophages can be accomplished either by activation of these cells by exposure to sensitized T-cell products, or by the introduction of exogenous peroxidase into the vacuole. Other factors influencing the ability of protozoa to survive intracellularly include the capacity of these organisms to avoid effective triggering of the macrophage respiratory burst and the levels of endogenous scavengers of oxygen products within the parasite.

Identification by immunofluorescence of eosinophil granule major basic protein in lung tissues of patients with bronchial asthma

To clarify the role of the eosinophil in asthma, tests were done to find out whether eosinophil granule major basic protein (MBP) is present at sites of epithelial damage in cases of asthma; this protein is toxic to respiratory epithelium and its levels are raised in the sputa of patients with asthma. The test used was an indirect immunofluorescence test, and the specimens tested were formalin-fixed, paraffin-embedded lung tissue obtained post mortem from patients with asthma and from control patients who had died of other diseases. The antiserum used was specific for MBP because it stained only eosinophils in the peripheral blood and because its activity was removed by absorption with MBP. Both controls and asthmatic patients had MBP in the cells, but patients dying of status asthmaticus also had extracellular MBP in mucus plugs, on damaged epithelial surfaces, and in necrotic areas below the basement membrane. Patients who had died of other diseases associated with severe asthma also had extracellular MBP in mucus plugs and on damaged epithelial surfaces. The results suggest that MBP in the eosinophil granule is released into respiratory tissue of patients with severe asthma and that it is associated with tissue damage.

Role for endogenous and acquired peroxidase in the toxoplasmacidal activity of murine and human mononuclear phagocytes

Oxygen products generated by the respiratory burst of mononuclear phagocytes are microbicidal to intracellular pathogens including Toxoplasma gondii. The toxicity of one of these products, H(2)O(2), is markedly amplified by the granule peroxidase of circulating phagocytes in the presence of a halide. Eosinophil peroxidase (EPO) binds firmly to the surface of T. gondii and such organisms remain viable as determined by vital staining, uptake of 2-deoxyglucose, and survival and replication in human fibroblasts. They are, however, rapidly killed by the addition of H(2)O(2) and iodide under conditions in which control organisms are unaffected. We have used EPO bound to T. gondii to explore the role of peroxidase in the toxoplasmacidal activity of mononuclear phagocytes. Resident mouse peritoneal macrophages lack a granule peroxidase and have a weak respiratory burst; toxoplasma survive and replicate within these cells. However, these cells acquire significant toxoplasmacidal activity, as assessed microscopically and by the inhibition of uracil uptake, when organisms are coated with EPO before ingestion, an effect which is decreased by the hemeprotein inhibitors, aminotriazole and azide. EPO on the surface of Toxoplasma does not increase their ingestion by macrophages or the associated respiratory burst. Monocytes from patients with hereditary myeloperoxidase deficiency have a significant toxoplasmacidal defect that is abolished when EPO-coated organisms are used. In contrast, the toxoplasmacidal defect of monocytes from chronic granulomatous disease patients is unaffected by surface-bound EPO. In these studies, replication of surviving intracellular organisms varied inversely with the magnitude of the respiratory burst: replication was greatest in fibroblasts, slightly less in resident macrophages, and least in monocytes; it was significantly greater in chronic granulomotous disease than in normal or myeloperoxidase-deficient monocytes. These studies support a role for oxygen products and endogenous peroxidase in the optimal killing of T. gondii by monocytes and demonstrate that peroxidase-negative phagocytes can utilize peroxidase on the surface of ingested organisms to augment microbicidal activity.

Eosinophil peroxidase-induced mast cell secretion

Eosinophil peroxidase (EPO) at relatively low levels (4-30 mU), when supplemented with H2O2 and a halide, induced mast cell degranulation. Histamine release occurred without concomitant release of the cytoplasmic marker lactic dehydrogenase (LDH), and this, together with ultrastructural studies, indicated a noncytotoxic effect comparable with that induced by other mast cell secretagogues. At pH 7.4, iodide was effective at concentrations down to 10(-5) M, and although chloride alone was ineffective at 0.1 M, a combination of 0.1 M chloride and 10(-6) iodide could meet the halide requirement. Chloride alone was effective at pH 6.5 and 6.0. EPO could be replaced by myeloperoxidase. When the EPO level was increased to 100 mU, combination with H2O2- and iodide-induced cytotoxic histamine release as indicated by concomitant LDH release and ultrastructural evidence of cell disruption. This cytotoxic response reverted to a secretory one on the addition of albumin. Peroxidase was detected on the surface of extruded granules by diaminobenzidine cytochemistry. The mast cell granule (MCG)/EPO complex when supplemented with H2O2 and iodide was more effective than free EPO in the stimulation of mast cell secretion. The stimulation of mast cell mediator release by the EPO-H2O2-halide system and the formation of MCG/EPO complexes with augmented cytotoxic activity may influence the adjacent inflammatory response.

The peroxidase activity of rat uterus

The peroxidase activity in the uterine extract of rats previously given a low dose of oestradiol has been examined. From sexually mature rats, two peroxidases of apparent molecular weights of 92 000 (peroxidase I) and 40 000 (peroxidase II) and of different mobilities in polyacrylamide disc gel electrophoresis were found. The two peroxidases were separated and characterized in terms of their substrate specificities, kinetics, pH optima for activity, inhibitors and stabilities. Both enzymes appeared to be classic haemoprotein peroxidases of very similar properties. Peroxidase II was further purified.

The occurrence of uterine stromal and intraepithelial monocytes and heterophils during normal late pregnancy in the rat

The steady decline in plasma progesterone level that occurs during the last week of pregnancy in the normal rat (Wiest, '70) provides good opportunity to study the effect of withdrawal of progesterone on uterine differentiation. Evidence is presented that tissue monocytes, heterophils, and eosinophils are regular components of the normal late gestational uterus and that their number increases as term approaches. Uterine monocytes and heterophils are located in the endometrial and myometrial stroma as well as within the basal intercellular compartment of the luminal epithelium. Stromal monocytes are distributed throughout the attenuated endometrium of late gestation, but are more common immediately beneath the luminal epithelium. In the myometrium, monocytes and heterophils occur, often as perivascular, clusters in the connective tissue septum that separates the two layers of smooth muscle. Eosinophils are present especially in the deep endometrial and myometrial stroma, and increase in number as plasma estrogen rises immediately before parturition. A small population of lymphocytes is regularly present. An important feature of the prepartum uterine stroma is the sparseness of macrophages. Near term, however, the beginnings of monocytic-macrophagic transformation are noticeable as the cell surface becomes more irregular and organelles associated with endocytic activity arise. The prepartum monocytes are positioned in the same histological sites that during the postpartum period of regression will be occupied by macrophages (Padykula and Campbell, '76). Since it is generally accepted that monocytes are precursors of macrophages, this spatial correlation raises the possibility that cellular preparations for regression commence before birth. The possible significance of prepartum monocytic infiltration is discussed in relation to the effect of changing plasma and uterine concentrations of progesterone on uterine collagenase activity. The steady increase in uterine leucocytes which occurs concomitantly with decreasing uterine binding capacity for progesterone supports the hypothesis by Siiteri et al. ('77) that progesterone in high local concentrations has an anti-inflammatory effect.