Secretory immunoglobulin binding to bacteria in the mouse uterus after mating

Epithelial cells in the female reproductive tract: a central role as sentinels of immune protection

The continued presence of bacterial and viral antigens in the lumen of the vagina coupled with the periodic presence of antigens in the lumen of the upper reproductive tract provide an ongoing challenge that can compromise female reproductive health and threaten life. Separating underlying tissues from luminal antigens, polarized epithelial cells of the cervix, uterus and Fallopian tubes have evolved to protect against potential pathogens. Once thought to function exclusively by providing a crucial barrier, mucosal epithelial cells are now known to function as sentinels that recognize antigens, respond in ways that lead to bacterial and viral killing, as well as signal to underlying immune cells when pathogenic challenge exceeds their protective capacity. Unique to epithelial cells of the female reproductive tract is the regulatory control of the female sex hormones. Acting both directly and indirectly through underlying stromal cells, estradiol and progesterone regulate epithelial cell innate and adaptive immune functions to protect against potential pathogens while providing an environment that supports an allogeneic fetus. In this article, we will outline how polarized epithelial cells function as the first line of defense against potential pathogens in the female reproductive tract.

Effect of Escherichia coli and Lactobacillus rhamnosus on macrophage inflammatory protein 3 alpha, tumor necrosis factor alpha, and transforming growth factor beta release by polarized rat uterine epithelial cells in culture

Entry of bacteria from the vagina into the uterus raises the question of uterine epithelial cell (UEC) signaling in response to the presence of bacteria. Our model system helps to define microbially elicited UEC basolateral cytokine release, important in regulating underlying stromal immune cell protection. UECs from adult rats were grown in cell culture inserts to establish a confluent polarized monolayer as was determined by transepithelial resistance (TER). Polarized epithelial cell cultures were treated apically with live or heat-killed Escherichia coli or Lactobacillus rhamnosus prior to collection of basolateral media after 24 h of incubation. Coculture of polarized UECs with live E. coli had no effect on epithelial cell TER. In response to exposure to live E. coli, epithelial cell basolateral release of macrophage inflammatory protein 3 alpha (MIP3 alpha) and tumor necrosis factor alpha (TNF-alpha) increased at a time when basolateral release of biologically active transforming growth factor beta (TGF-beta) decreased. Incubation of UECs with heat-killed E. coli resulted in an increased basolateral release of MIP3 alpha and TNF-alpha, without affecting TER or TGF-beta. In contrast to E. coli, live or heat-killed L. rhamnosus had no effect on TER or cytokine release. These studies indicate that polarized rat UECs respond to gram-negative E. coli by releasing the cytokines MIP3 alpha and TNF-alpha, signals important to both the innate and adaptive immune systems. These findings suggest that UEC responses to bacteria are selective and important in initiating and regulating immune protection in the female reproductive tract.

MUC1/episialin: a critical barrier in the female reproductive tract

The female reproductive tract must resist microbial infections as well as support embryonic development, implantation and placentation. Reproductive tract mucins, in general, and Muc1/episialin, in particular, play key roles in implantation related events and in protection from microbial infection. High levels of mucin expression in the lower reproductive tract presumably affords protection against infection while down-regulation of uterine mucins has been suggested to provide access to the uterine surface. The present studies demonstrate that mucins, particularly Muc1, are effective barriers to embryo attachment. Furthermore, a strain of female Muc1 null mice in normal housing displays chronic infection and inflammation of the lower reproductive tract and markedly reduced fertility rates. This phenotype is not observed when Muc1 nulls are housed in a pathogen-free environment indicating that this phenotype results from chronic microbial exposure. Only normal endogenous flora were isolated from the reproductive tracts of affected Muc1 null mice, suggesting that these bacterial species become opportunistic with loss of the mucin barrier. Staphylococcal adherence to lower reproductive tract epithelia was found to be mediated by cell surface mucin carbohydrates. Collectively, these studies demonstrate a critical barrier role for Muc1 in various aspects of female reproductive tract physiology.

Secretion of Salmonella-specific antibodies in the oviducts of hens experimentally infected with Salmonella enteritidis

The production and secretion of Salmonella enteritidis whole cell antigen-specific antibodies in the oviducts and in the serum of laying hens experimentally infected with Salmonella enteritidis, was analyzed by ELISA. The dynamics of the antibody levels in the oviducts were identical to that in the serum. Subclasses of antibodies (IgA, IgG, and IgM) in the infected hens were found to increase significantly (p < 0.01) compared to those in the control uninfected hens throughout the experiment. IgG and IgM levels in both oviducts and in sera reached to a peak by 14 days post-inoculation, and remained elevated throughout. The secretion of IgA seemed to be transient since the IgA levels increased to a peak 7 days after both primary and secondary inoculations, and declined rapidly. The elevated levels of antibodies were followed by partial clearance of Salmonella organisms from the oviducts. The present results indicate a significant local immune reaction against the Salmonella infection and suggest an association of the local antibodies with the clearance of Salmonella from the oviducts at least partially.

Specific secretory immune responses in the female genital tract following intranasal immunization with a recombinant adenovirus expressing glycoprotein B of herpes simplex virus

Previously, we demonstrated that intranasal (i.n.) but not intraperitoneal (i.p.) immunization with a recombinant adenovirus vector expressing glycoprotein B (gB) of herpes simplex virus type 1 (HSV-1) induced mucosal immune responses and conveyed long-term protection to mice against an i.n. challenge with heterologous HSV-2. We now show that i.n. immunization of female mice with this same vector, AdgB8, provides secretory and serum-derived humoral immune responses in the genital tract. Intranasal immunization induced anti-HSVgB IgA and IgG in vaginal washes of mice, whereas i.p. immunization only induced IgG, which appeared to be serum-derived. Interestingly, intravaginal (ivag) immunization with AdgB8 resulted in little or no anti-HSVgB IgA and only low levels of specific IgG in vaginal washes. All three routes of inoculation induced gB-specific serum IgG and IgA; however, i.n. immunized mice demonstrated the highest level of serum anti-HSVgB IgA. Additionally, ivag boosting with AdgB8 did not significantly alter the serum or vaginal wash antibody responses in i.n. or i.p. immunized mice. The IgG to IgA ratios of gB-specific and total antibody titres in the serum and vaginal washes of i.n. immunized mice indicated that the IgA in the vaginal washes was likely to be secretory. Furthermore, the titres of anti-HSVgB IgA relative to total IgA were higher in vaginal washes than sera, suggesting that the gB-specific vaginal wash IgA present in i.n. immunized mice was locally produced.

A study of the microbial flora of the anterior vagina of normal sows during different stages of the reproductive cycle

Sterile guarded swabs were used to sample the anterior vaginal and cervical area of 23 normal healthy sows during various stages of the reproductive cycle. The samples were collected one week before farrowing, within 24 hours of farrowing, weekly up to weaning, at mating and at 2 and 3 weeks after mating, and then plated and incubated aerobically and anaerobically. At least one positive sample was obtained from each sow and at each stage of the reproductive cycle. Most positive samples (78.3%) were obtained on the day of farrowing and the least 3 weeks after mating (19.0%). The second highest number of positive samples (45.5%) was found immediately after mating. Although there was no significant difference among sows of different parities, there was a trend for older sows to have more positive samples after farrowing (84.6%). There was a greater decrease in positive samples after farrowing and after mating among younger sows compared with older sows. A wide range of bacteria including aerobic and anaerobic species, were recovered from 142 isolates. The more representative bacteria were Streptococcus spp (23.2%); Escherichia coli (22.5%); Staphylococcus spp (19.0%) and Corynebacterium spp (13.4%). Of the cultures, 54.7% were pure and 45.3% were mixed. Both the percentage of bacterial isolates as well as the type of culture (pure or mixed) were similar to those frequently reported in clinical cases of vulval discharge syndrome. The results indicate that sows usually develop infections of the reproductive tract at farrowing and mating but these infections do not normally persist.

WGA-binding, mucin glycoproteins protect the apical cell surface of mouse uterine epithelial cells

Expression of apical cell surface proteins and glycoproteins was examined in polarized primary cultures of mouse uterine epithelial cells (UEC). Lectin-gold cytochemistry revealed that wheat germ agglutinin (WGA) bound specifically to the components of the apical glycocalyx as well as intracellular vesicles. Double labeling with the pH sensitive dye 3-(2,4-dinitroanilino)-3'amino-N-methyldipropylamine (DAMP) demonstrated the acidic nature of the WGA-staining intracellular vesicles. The enzymatic and chemical sensitivities of the WGA binding sites on the apical cell surface were monitored both by WGA-gold staining as well as by 125I-WGA binding assays. In thin sections, a large fraction of these sites were removed by pronase; however, application of a wide variety of proteases, glycosidases, or chemical treatments to the apical surface of intact UEC failed to reduce WGA binding. In no case did treatments designed to remove sialic acids reduce 125I-WGA binding more than 12%. In contrast, endo-beta-galactosidase as well as a combination of beta-galactosidase with beta-hexosaminidase succeeded in removing 28% and 77% of these sites, respectively. These studies suggested that the majority of the apically disposed WGA binding sites involved N-acetylglucosamine residues rather than sialic acids and included lactosaminoglycans. Many of the proteins detected at the apical cell surface by lactoperoxidase-catalyzed radioiodination were WGA-binding glycoproteins. A major class of these glycoproteins displayed Mr > 200 kDa by SDS-PAGE and was heavily labeled metabolically by 3H-glucosamine or by vectorial labeling at the apical cell surface with galactosyl transferase and UDP-3H-galactose. Analyses of the 3H-labeled oligosaccharides labeled by either procedure indicated that a large fraction of the apically disposed WGA-binding oligosaccharides consisted of neutral, O-linked mucin-type structures with median MW of approximately 1,500. Oligosaccharides in this fraction were partially (15%) sensitive to endo-beta-galactosidase digestion and bound to Datura stramonium agglutinin (68%), demonstrating the presence of lactosaminoglycan sequences. UEC were an extremely effective barrier to attachment or invasion by either a highly invasive melanoma cell line, B16-BL6, or implantation-competent mouse blastocysts. In contrast, neither uterine stromal cells nor a non-polarizing UEC cell line, RL95, prevented B16-BL6 attachment.(ABSTRACT TRUNCATED AT 400 WORDS)

Immunoglobulins and monoclonal anti-blastocyst antibodies in the mouse uterine secretion during the early pre-implantation period

A Sepharose bead blot technique was used to study immunoglobulins in the uterine secretion of mice during the pre-implantation stage. Secretion collected by Sepharose beads contained IgA, IgG, and IgM. The method could be made ten-fold more sensitive by using anti-mouse IgG or IgM conjugated to Sepharose beads. It has also been demonstrated that when injected intravenously, biotinylated purified immunoglobulins, both non-specific mouse myeloma IgG and IgM and specific anti-blastocyst IgG and IgM, is able to pass into the uterine cavity of the mouse. It was further shown that when injected systemically, anti-blastocyst antibodies can reach the blastocyst. Functionally active specific antibodies against morulae and/or blastocysts may, therefore, be able to influence the pre- and peri-implantation development of the embryo and could serve as a useful model for experiments directed towards the identification of immunological contraceptive procedures.

The immune function of the endometrium

The endometrial mucosa is unique amongst mucosal sites in that it must mount an immune response against micro-organisms and resist tumour growth whilst tolerating sperm and the allogeneic fetus. Bacterial and viral infection in the uterus leads to local endometrial mucosal immune responses evidenced by the secretion of secretory component (SC), secretory IgA (sIgA) and IgG. The secretion of these molecules is under hormonal control. Trafficking of locally sensitized lymphocytes to other mucosae does not appear to occur, whereas priming at other mucosal surfaces leads to memory responses to antigen in the uterus. Proclivity to local immune function is related to sparse lymphatic supply to the endometrium together with a local distribution of antigen-presenting dendritic cells. During pregnancy, particularly in the region of the decidua and embryo, the number of Ia+ cells and the lymphatic supply become diminished. The antigenic status of sperm may lead to certain types of maternal sensitization. However, immunosuppressive factors in seminal plasma protect the sperm on its passage up the female genital tract and diminish subsequent immunogenicity. On fertilization of the oocyte, an allogenic fetus develops, that potentially could stimulate production of maternal immune effectors. Endometrial cells of various types (macrophage, decidual, NK, T cells) interact via soluble factors leading to a local immunoprotection of the fetus. Similar factors appear to operate in resisting tumour growth in the uterus.

Anti-bacterial IgA and IgG in mouse uterine luminal fluid, vaginal washings and serum

A previous study demonstrated that mouse uterine horns contained bacteria of several species on the morning after mating, and immunolabeling showed that many of these bacteria were coated with immunoglobulins. In the present study we used an ELISA technique to detect naturally-occurring antibodies against bacteria in mouse uterine luminal fluid, vaginal washings and serum. Each fluid contained specific IgA and/or IgG antibodies to five of the six bacterial species recovered from the uterus after mating. The uterine fluid antibodies that bound to the bacteria were mainly IgA molecules, while those in the serum were mainly IgG. Naturally-occurring bacterial antibodies in mouse uterine luminal fluid may play a role in protecting the endometrium against microbial infections.

Endocytosis in the uterine luminal and glandular epithelial cells of mice during early pregnancy

We have localized horseradish peroxidase (HRP) in the mouse uterus after intravenous administration on days 1 and 5 of pregnancy in an effort to understand how serum proteins reach the uterine lumen. Direct movement of HRP into uterine and glandular lumina was blocked by the epithelial tight junctions on both days. In luminal and glandular epithelial cells at both times, HRP was localized in endocytic vesicles along the basolateral membranes, multivesicular bodies (mvb), elongated dense bodies below the nucleus (bdb), and many small vesicles near the apical surface of the cells. The uptake of HRP was most extensive in the luminal epithelium on day 1: the number of tracer-containing apical vesicles and bdb was largest, and there were also clusters of vesicles containing the tracer above the nucleus. Acid phosphatase was localized on day 1 in mvb and bdb in both cell types, indicating that these structures are lysosomes. It appeared that HRP followed two pathways after basolateral endocytosis by the epithelial cells: it was transported to the apical region of the cells, where it was present in small vesicles that may release their contents into the uterine or glandular lumina, or it was transported to lysosomes. To investigate whether macromolecules may be transported from the uterine lumen to the stroma, we also studied endocytosis at the apical pole of luminal epithelial cells after intraluminal injection of HRP. There was no detectable uptake of HRP from the lumen on day 1, and no tracer was detected in the intercellular spaces or basement membrane region. On day 5, a large amount of HRP was taken up from the lumen into apical endocytic vesicles, mvb, and dense bodies, but tracer was not present in the Golgi apparatus, lateral intercellular spaces, or the basement membrane region at the times studied. These observations indicate that there was no transport of luminal macromolecules to the uterine stroma on day 1, while the possibility of transport on day 5 requires further study.

Deposition of C3 on bacteria in the mouse uterus after mating

A previous study demonstrated that several species of bacteria were present in the mouse uterine lumen on the day after mating, and that many of these bacteria had immunoglobulins bound to their surface. Neutrophilic leukocytes containing phagocytosed bacteria were also present in the lumen. Since bacteria are phagocytosed efficiently only when they are opsonized by the binding of specific antibody or C3b or both to their surface, we investigated whether the uterine bacteria were coated with C3. Immunolabeling demonstrated that an antigenic portion of C3, possibly C3b, was bound to many of the uterine bacteria. This observation suggests that bacteria in the mouse uterus after mating may be opsonized by both antibody and complement and that phagocytosis of these bacteria by neutrophils may play an important role in returning the uterus to an aseptic state before implantation.

Uptake of immunoglobulins and other proteins from serum into epithelial cells of the mouse uterus and oviduct

The transport of immunoglobulins into the lumen of the female reproductive tract is not well understood, especially in the case of IgG. In mice, there are conflicting reports concerning the presence of immunoglobulins in uterine luminal and glandular epithelial cells, and immunoglobulins have not been detected in the luminal epithelial cells of the oviduct. In the present study we detected both IgA and IgG in uterine luminal and glandular epithelial cells on day 1 of pregnancy by immunolabeling. Also, we observed that fluorescein-conjugated mouse and bovine IgG and other proteins were taken up into vesicles in uterine luminal and glandular epithelial cells after intravenous administration. These observations indicate that both kinds of epithelial cells take up immunoglobulins from the interstitial fluid on day 1 of pregnancy, and that the cells may therefore be involved in the transport of immunoglobulins and other proteins to the uterine lumen at that time. In the oviduct, we detected IgA and IgG in vesicles in the luminal epithelial cells of the preampulla by immunolabeling, and we observed fluorescein-conjugated IgA and IgG in similar vesicles after intravenous administration. The presence of IgA and IgG in vesicles in the epithelial cells of the preampulla, together with the previous demonstration of plasma cells of both isotypes and large amounts of interstitial immunoglobulins in the lamina propria of this segment, suggests that the preampulla of the oviduct may be an important site for the local immune system in the mouse female genital tract.

The effect of sperm immunization in the gastrointestinal tract on anti-sperm antibody production and fertility in female mice

The present investigation studied the effects of sperm immunization in the gastrointestinal tract on anti-sperm antibody production and fertility in female mice. For comparative purposes, mice were also immunized with sperm intraperitoneally. Intraperitoneal immunization with 5 X 10(6) washed epididymal and vas deferens sperm 3 times per week for 7 wk produced anti-sperm IgG in plasma at 1:20,000 and in vaginal washings at 1:100 as determined by ELISA. Such mice have been shown previously to have reduced fertility. In comparison, mice immunized intragastrically with 5 X 10(6) sperm once per week for 11-14 wk had anti-sperm IgA in vaginal washings at only about 1:8 as determined by ELISA. After mating at the 14th wk these mice delivered 6.5 +/- 1.4 pups, which was not significantly different from the 7.1 +/- 1.1 pups delivered by an untreated control group. Mice immunized twice intragastrically and once intravaginally during a 25-day period had no detectable anti-sperm IgA in vaginal washings by ELISA. These mice delivered 9.7 +/- 1.2 pups after mating beginning on day 32, as compared to 9.7 +/- 0.8 pups in a PBS-sham immunized group. Mice immunized once intraduodenally and then once intraperitoneally 14 days later delivered 10.4 +/- 0.9 pups after mating 10-14 days after the second immunization, while a similar group of mice whose primary sperm immunization was directly into Peyer's patches delivered 9.0 +/- 1.4 pups. We could not detect anti-sperm IgG or IgA bound to sperm in the uterine or oviduct lumen using immunohistochemical labeling after any of the groups of immunized mice were mated.(ABSTRACT TRUNCATED AT 250 WORDS)

Localization of immunoglobulins in the mouse uterus, embryo, and placenta during the second half of pregnancy

Throughout the second half of pregnancy in mice there were many plasma cells containing immunoglobulins A (IgA) and G (IgG) in the uterine endometrium. There was intense staining of IgA in uterine glands at all stages, but little staining of IgG. The staining of both immunoglobulins (Igs) in the luminal epithelium was moderate to dark on day 11, slight on day 14, and increased from day 16 to term. From day 14 to term the endometrium exhibited folds or villi around each placenta. The cores of the villi contained many plasma cells of both isotypes, and the staining of extracellular Igs in the villous cores was darker than in nonvillous endometrium. Both Igs were detected in the uterine lumen, and in visceral and parietal yolk sac endoderm cells at all stages. Near term, the staining of Igs in the visceral yolk sac was darkest in the peripheral villous portion adjacent to the endometrial villi. From day 14 to term IgG was present in the visceral yolk sac mesenchyme and embryo, consistent with its transfer from the uterine lumen to the embryo via the vitelline circulation. In contrast, IgA was not detected in yolk sac mesenchyme until day 19, when only slight staining was observed, and IgA was never detected in the embryo. Most trophoblast giant cells contained both Igs on day 11. During the remainder of pregnancy, there was staining of both Igs in labyrinthine trophoblast and in a few giant cells adjacent to the parietal yolk sac on the placenta, but there was negligible staining in the spongiotrophoblast region. Our observations suggest that the local immune system in the mouse uterus may protect the embryo during the second half of pregnancy by secreting anti-microbial immunoglobulins A and G into the uterine lumen surrounding the visceral yolk sac, and may at the same time contribute to the transfer of maternal IgG to the embryo via the yolk sac and vitelline circulation.