Asymmetric antibodies (AAb) in the female reproductive tract

The Emerging Importance of IgG Fab Glycosylation in Immunity

Human IgG is the most abundant glycoprotein in serum and is crucial for protective immunity. In addition to conserved IgG Fc glycans, ∼15-25% of serum IgG contains glycans within the variable domains. These so-called "Fab glycans" are primarily highly processed complex-type biantennary N-glycans linked to N-glycosylation sites that emerge during somatic hypermutation. Specific patterns of Fab glycosylation are concurrent with physiological and pathological conditions, such as pregnancy and rheumatoid arthritis. With respect to function, Fab glycosylation can significantly affect stability, half-life, and binding characteristics of Abs and BCRs. Moreover, Fab glycans are associated with the anti-inflammatory activity of IVIgs. Consequently, IgG Fab glycosylation appears to be an important, yet poorly understood, process that modulates immunity.

Progesterone induces mucosal immunity in a rodent model of human taeniosis by Taenia solium

More than one quarter of human world's population is exposed to intestinal helminth parasites. The Taenia solium tapeworm carrier is the main risk factor in the transmission of both human neurocysticercosis and porcine cysticercosis. Sex steroids play an important role during T. solium infection, particularly progesterone has been proposed as a key immunomodulatory hormone involved in susceptibility to human taeniosis in woman and cysticercosis in pregnant pigs. Thus, we evaluated the effect of progesterone administration upon the experimental taeniosis in golden hamsters (Mesocricetus auratus). Intact female adult hamsters were randomly divided into 3 groups: progesterone-subcutaneously treated; olive oil-treated as the vehicle group; and untreated controls. Animals were treated every other day during 4 weeks. After 2 weeks of treatment, all hamsters were orally infected with 4 viable T. solium cysticerci. After 2 weeks post infection, progesterone-treated hamsters showed reduction in adult worm recovery by 80%, compared to both vehicle-treated and non-manipulated infected animals. In contrast to control and vehicle groups, progesterone treatment diminished tapeworm length by 75% and increased proliferation rate of leukocytes from spleen and mesenteric lymph nodes of infected hamsters by 5-fold. The latter exhibited high expression levels of IL-4, IL-6 and TNF-α at the duodenal mucosa, accompanied with polymorphonuclear leukocytes infiltration. These results support that progesterone protects hamsters from the T. solium adult tapeworm establishment by improving the intestinal mucosal immunity, suggesting a potential use of analogues of this hormone as novel inductors of the gut immune response against intestinal helminth infections and probably other bowel-related disorders.

New target cells of the immunomodulatory effects of progesterone

It is well known that the reproductive steroid hormones, particularly progesterone, in addition to its widely recognized effects on endometrial epithelial and stromal cells and spiral arteries, affect the activities of T cells and natural killer cells in the deciduas, thus inducing active immune tolerance against the fetal antigens. The immunomodulatory effects of progesterone on T cells, B cells and natural killer cells have been discussed extensively in the literature. The aim of the present review is to sum up and discuss the results from this and other laboratories of investigations on the effects of progesterone on dendritic cells and adult stem cells, which are some of the other cell populations present at the fetal-maternal interface and possibly are related to the immunoregulation during pregnancy. These cells have been shown to have a number of specific functions but their involvement in the entire process of regulation of the immune response in pregnancy is still under discussion. The present review focuses on facts showing that the progesterone is a kind of 'regulator of regulators' in the decidua, thus creating the most favourable conditions for the development of the semi-allogeneic fetus in successful pregnancy.

Dehydroepiandrosterone to induce murine models for the study of polycystic ovary syndrome

During the last decade a battery of animal models used for the study of polycystic ovary syndrome (PCOS) have allowed a focus on different aspects of the pathology. Since dehydroepiandrosterone (DHEA) was found to be one of the most abundant circulating androgens in women with PCOS, a rodent model showing the salient features found in women with PCOS was developed by the injection of DHEA. Although insulin-sensitizing agents, such as biguanides, are clinically used in the treatment of diabetes and PCOS, the complete understanding of their mechanisms of action remains unknown. The present review discusses the molecular mechanisms involved in the development of PCOS by using the DHEA-PCOS murine model and analyzes the role of the biguanide metformin as treatment.

The persistence of paternal antigens in the maternal body is involved in regulatory T-cell expansion and fetal-maternal tolerance in murine pregnancy

PROBLEM

Mammalian pregnancy is a state of immunological tolerance and CD4(+) CD25(+) regulatory T cells (Treg) contribute to its maintenance. Knowing that Treg act in an antigen-specific way during pregnancy, we hypothesized that they are generated after maternal immune cells encounter paternal antigens.

METHOD OF STUDY

We mated wild type females with transgenic green fluorescent protein (GFP) males in an allogenic setting and killed them on different days of pregnancy.

RESULTS

Presence of paternal and maternal MHC class II(+) cells in vaginal lavage on day 0.5 of pregnancy was confirmed. Thus, antigen presentation may take place early during pregnancy in the periphery either by the direct or indirect pathways. Foxp3(+) cells known to have regulatory activity could be detected on day 2 of pregnancy in lymph nodes and shortly after implantation at the fetal-maternal interface.

CONCLUSION

Our data suggest that paternal antigens are processed early during pregnancy, which leads to the generation of Treg. The continuous release of placental antigens into the maternal circulation allows the maintenance of a Treg population which is specific for paternal antigens and mediates tolerance toward the semi-allogeneic fetus until the time point of birth.

Dehydroepiandrosterone and metformin modulate progesterone-induced blocking factor (PIBF), cyclooxygenase 2 (COX2) and cytokines in early pregnant mice

The present study examined the mechanism by which metformin (N,N'-dimethylbiguanide) prevents embryonic resorption induced in mice by dehydroepiandrosterone (DHEA). Treatment with DHEA (60mg/kg, s.c. 24 and 48h post-implantation) induces embryo resorption of early pregnant BALB/c mice while simultaneous treatment with metformin (240mg/kg, oral 24 and 48h post-implantation) prevents it. During pregnancy progesterone-induced blocking factor (PIBF) modulates prostaglandins (PGs) and cytokine production. These findings prompted us to investigate the effect of DHEA and metformin on both PIBF and cyclooxygenase 2 (COX2) expressions at the implantation sites, as well as cytokine production. PIBF and COX2 expression were detected by immunohistochemistry from DHEA and DHEA+ metformin treated 8 days-pregnant mice and serum cytokine levels of these animals were determined by ELISA. DHEA treatment both abolished PIBF expression and increased COX2 expression. Embryo resorption correlates with the lack of PIBF expression, diminished IL-6 levels and increased IL-2 concentration while metformin was able to reverse the effect of DHEA on both PIBF and COX2 expression and IL-6 levels. We concluded that hyperandrogenization induces embryo resorption in early pregnancy diminishing PIBF in implantation sites, having a pro-inflammatory effect. Metformin is able to prevent such effects.

Kinetics of regulatory T cells during murine pregnancy

PROBLEM

The semi-allogeneic fetus is usually tolerated by the maternal immune system. This was proposed to be modulated by CD4+CD25+foxp3+ regulatory T cells (Treg). We aimed to determine the kinetics of Treg during murine gestation and investigate whether changes in Treg levels respond to hormonal variations during pregnancy or generated changes in the local indolamine dioxygenase (IDO) expression.

METHOD OF STUDY

We included in our studies the well-known CBA/JxDBA/2J abortion-prone combination using CBA/JxBALB/c as controls. CBA/JxC57/BL6 and BALB/cxC57/BL6 were included as further controls. Animals were killed on days 0, 2, 5, 8, 10, and 12 of pregnancy to measure the levels of Treg, pregnancy-related hormones and IDO expression.

RESULTS

A Treg augmentation in normal pregnancy combinations could be observed on day 2 in several organs contrary to the observations made in abortion-prone mice. No differences in hormonal levels could be seen among all groups. IDO was expressed exclusively in placenta starting from day eight, showing no variations among the groups.

CONCLUSION

Differences in Treg levels and pregnancy outcome do not correlate with changes in hormonal levels. In addition, as Treg augmentation takes place early and it is observed mainly in the decidual component of the fetal-maternal interface, IDO does not seem to be the pathway underlying Treg protective activity as proposed for humans.

Immunological analogy between allograft rejection, recurrent abortion and pre-eclampsia - the same basic mechanism?

There are still controversies concerning the role of immunological mechanisms engaged both in recurrent abortions (RA) and pre-eclampsia (PE). According to some opinions, recurrent miscarriage is comparable to organ-specific autoimmune disease. Analysis of immune reactions shows that graft rejection shares many similar mechanisms with RA and PE. This fact allows us to conclude that rejection of transplanted alloantigenic organs and pregnancy loss have probably the same evolutionary origin. Subsets and functions of immunocompetent cells (T CD4, suppressor gammadeltaT, cytotoxic T CD8, Treg, Tr1, uterine NK cells), over-activation of innate immunity (activation of NK cytotoxic cells, macrophages, neutrophils and complement), changes of Th1/Th2 cytokine balance (IL-2, IL-12, IL-15, IL-18, IFNgamma, TNFalpha vs. IL-4, IL-10, TGFbeta), importance of HLA-G molecule, CD200/CD200R interaction, over-expression of adhesion molecules, fgl2 prothrombinase activation and stimulation of IDO and HO expression, all suggest that RA and PE are syndromes of fetal allograft rejection, and not organ-specific autoimmune diseases. According to that supposition, an analogy might exist between acute graft rejection and recurrent abortion, and between chronic graft rejection and pre-eclampsia.