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Pregnancy involves adaptations of the cellular composition in utero to establish a functioning fetal-maternal interface. Different subsets of leukocytes populate the endometrium and contribute to tolerance of the fetal allograft while protecting it from potentially threatening infections or rejection. ¬¬Innate lymphoid cells are recently discovered immune cells that, besides the gut, lung and skin, possess immunoregulatory functions in the female reproductive tract, especially during gestation. Although present at the fetal-maternal interface, the dynamics of ILC migration during pregnancy remains poorly investigated. The involvement of homing receptors in ILC migration to the uterus was the main subject of the present work.
First, the expression of homing receptors on ILCs from miscellaneous organs was assessed across the course of murine pregnancy in vivo by means of flow cytometry. Then, their migratory capacity towards pregnancy-relevant chemokines was investigated in vitro. The impact of pregnancy related hormones on the migration and homing of ILCs was then analysed in vitro via migration assays.
The results confirm altered proportions of ILCs in utero and the altered expression of homing receptors in ILCs in pregnancy. Different murine lymphoid organs showed augmented expression of chemokine receptors and decreased levels of homing integrin α4β7 in the first trimester, suggesting enhanced migration patterns of ILCs during early pregnancy. Subsequently, migration assays were used to demonstrate the role of different chemokine ligands in enhancing ILC migration.
Eventually, the alterations in homing receptor expression were correlated with female pregnancy hormones. Progesterone treatment caused similar effects on homing receptor expression in ILCs as observed during early gestation. These results represent the first study evaluating the effect of sex steroid hormones on ILC chemokine receptor distribution.
Taken together, our results indicate the involvement of pregnancy-relevant chemokines, including CCL4, CCL20 and CCL28, in the recruitment of ILCs to the uterus during pregnancy. The data highlight an endocrinological-immune crosstalk in the regulation of ILC homing to the female reproductive tract. Gestation alters chemokine receptor expression in order to regulate the access of immune cell subsets to the fetal-maternal interface. An adequate regulation is highly needed, as a lack or abundance of different subgroups could result in pregnancy complications, including fetal loss, pre-eclampsia or pre-term birth. Thus, the role of ILC chemotaxis to the pregnant uterus and its regulation are of interest in the understanding, prevention and treatment of the clinically relevant obstetric diseases.
Gynaecologic immunologic research aims to answer an important question: How does the immune system manage to protect both mother and unborn child while not harming the semi-allogeneic and thus partially unaccustomed fetus? Several distinct adaptions in both the innate and adaptive immune system take place during pregnancy. Alterations in these processes can cause dramatic consequences like pregnancy loss. Here, molecules with immunomodulatory functions can provide possible treatment options. One molecule with the described features emerged as a candidate: The transmembrane molecule mCD83 as well as its soluble form, sCD83. As mCD83 overexpressing cells and cells from pregnant mice showed similar behaviour regarding interleukin-10 secretion and B-cell (BC) development, a contribution of mCD83 in immunologic pregnancy adaptions is possible. Additionally, the soluble form could be a future therapeutic agent in pregnancy disorders, regarding its already shown benefits in therapy of various autoimmune diseases in animal models.
The aim of this work is to evaluate the expression, release and regulation of CD83 in its membrane bound and soluble forms during normal and disturbed pregnancies in mouse models.
The semi-allogeneic pairing of two inbred stems, C57Bl6/J×BALB/c, results in healthy pregnancy and was used to investigate the expression in different stages of pregnancy. Pairing CBA/J females with DBA/2J males results in resorption of fetal units and represents a poor pregnancy outcome mating (PPOM). This model in comparison with CBA/J×BALB/c pairings (presenting a good pregnancy outcome mating (GPOM)) is a model for immunologic pregnancy disturbance. It was used to detect alterations in mCD83 expression and sCD83 release during disturbed pregnancy.
During normal murine pregnancy, mCD83 expression increased with a peak on day 14 of pregnancy on B- and T-cells, while the amount of mCD83 positive cells was elevated at the end of pregnancy. PPOM mice showed higher mCD83 expression and mCD83 positive cell count on various lymphocyte subtypes in comparison to GPOM, while sCD83 levels were lower in PPOM pregnancies. Splenocytes released sCD83 in cell culture, whereby the main part under unstimulated conditions was produced by BC. Progesterone treatment of splenocytes led to a dose dependent mCD83 upregulation on T-cells and reduced mCD83 expression as well as sCD83 release from BC. Culture of splenocytes with tissue inhibitor of metalloproteinases 1 (TIMP1) resulted in elevated sCD83 release and mCD83 expression on BC. Progesterone reduced TIMP1 expression on BC in vitro.
mCD83 expression and sCD83 release showed various alterations during normal murine pregnancy as well as when comparing PPOM with GPOM. Noticeable are in particular a higher mCD83 expression on splenic BC on day 14 of pregnancy. In BC from PPOM, mCD83 expression is higher than on BC from GPOM, while PPOM mice show a lower sCD83 serum level, hinting a problem in the shedding mechanism during PPOM.
Progesterone regulates mCD83 expression on BC via TIMP1 and a yet unknown proteinase, resulting in degradation of mCD83 with lower mCD83 expression and sCD83 release. Here, the resulting expression level may vary depending on the BC surroundings and cell compartmentation.
The results thereby suggest a CD83 involvement in pregnancy and encourage further research on mCD83 expression at the feto-maternal interface as well as sCD83 in human blood and tissue. Especially the sCD83 alterations are of clinical interest, indicating the molecule as potential therapeutical option for pregnancy disturbances.
Introduction: For a successful pregnancy, a set of physiological requirements has to be fulfilled. The mother has to provide enough nutrients and the proper anatomical environment for the developing fetus and protect him and herself against pathogens. The cells of the im-mune system constantly monitor the organism in search for pathogens and mount a response to eradicate the threat. The favourable outcome of an immune response re-lays on the capacity of those cells to recognize structures that shouldn’t be present in the organism and the speed or strength at which the cells react. During pregnancy, however, a fetus is able to establish a firm contact with the endometrium of the mother and then grow for an extended period of time. This “exception to the rule” hides behind a set of fine-tuned regulations of the immune responses which are not completely un-derstood. Though many cell types have been extensively investigated in the past dec-ades, B cells play yet enigmatic roles. The aim of this work is to uncover the events occurring within the B cell development during pregnancy and to study the role of certain subtypes in healthy pregnancy and pregnancy miscarriage. Methods: For all experiments, 8-weeks-old female mice either non-pregnant, having normal preg-nancies or miscarriage were used. Organs were removed and cells isolated using standard protocols. The analysis of the population distribution was performed by Flow Cytometry. For in vitro experiments, specific cell subsets were isolated using MACS Cell Separation. Bio-plex method was used for the assessment of Immunoglobulin isotypes in serum, while CBA Array was the method used to measure cytokine levels in the supernatant of cell cultures. Statistical analysis was done using GraphPad Prism software. Results: Pregnancy had a strong impact on the murine B cell development. The restructuration of the B cell compartment could be appreciated already from the bone marrow progeni-tors, reduced in pregnant mice. Peripheral subsets drastically adapted their develop-mental pathways, with a drift towards the generation of marginal zone B cells. B cells also showed functional adaptations to gravidity, as evidenced by the changes in the immunoglobulin production and immunomodulatory capacity. Conclusions: For the first time a deep investigation of the consequences of pregnancy on the B cell development was performed, covering several aspects of B cell functionality. This work shows that B lymphocyte compartment is remodelled during pregnancy. Aberration of this process may lead to pregnancy complications including miscarriage.