André Sollwedel

Abnormal T-cell reactivity against paternal antigens in spontaneous abortion: adoptive transfer of pregnancy-induced CD4+CD25+ T regulatory cells prevents fetal rejection in a murine abortion model.

Mammalian pregnancy is thought to be a state of immunological tolerance. The mechanisms underlying this phenomenon are still poorly understood. Here, we determined whether an inappropriate function of T regulatory (Treg) cells is involved in the pathogenesis of spontaneous abortion. We evaluated spleen and decidual lymphocytes from CBA/J mice undergoing immunological abortion (DBA/2J-mated) or having normal pregnancy (BALB/c-mated) on day 14 of gestation for ex vivo cytokine production after PMA or paternal antigen (alloantigen) stimulation. Treg activity was characterized by quantifying CD4(+)CD25(+) cells, foxp3 expression, and interleukin-10 secretion. Decidual lymphocytes from abortion CBA/J mice contained a significantly higher frequency of interferon-gamma-producing T cells specific for paternal antigens compared to those from normal pregnancy (7.8% versus 2.7%, P < 0.05). Compared to virgin CBA/J females, normal pregnant mice showed strongly elevated numbers of CD4(+)CD25(+) and interleukin-10(+) Treg cells in the thymus whereas significantly lower frequencies of Treg cells were observed in abortion mice. Very interestingly, CD4(+)CD25(+) Treg cells from normal pregnant and nonpregnant CBA/J mice could inhibit both proliferation and interferon-gamma secretion of lymphocytes from abortion mice in vitro whereas in vivo prevention of fetal rejection could only be achieved after adoptive transfer of Treg cells from normal pregnant mice. Our data suggest that pregnancy-induced Treg cells play a vital role in maternal tolerance to the allogeneic fetus.

Pre‐eclampsia is not Associated with Changes in the Levels of Regulatory T Cells in Peripheral Blood

The acceptance of the semi‐allogeneic fetus within the maternal environment requires tolerance mechanisms not fully characterized yet. Normal pregnancy is known to be associated with a Th2 profile. Furthermore, regulatory T cells (Tregs) were proposed to regulate the Th2/Th1 balance at early stages of pregnancy. Treg may avoid the shift to a Th1 profile, thus preventing miscarriage. Accordingly, spontaneous abortion is characterized by a Th1 dominance and diminished levels of Treg. The major aim of the present work was to investigate if pre‐eclampsia, a late immunological complication of pregnancy, is characterized by similar hallmarks.

Mechanisms of action of regulatory T cells specific for paternal antigens during pregnancy.

OBJECTIVE: To investigate whether pregnancy-induced regulatory T cells are generated specifically for paternal antigens or expanded by hormonal changes and to study regulatory T cell–related mechanisms during pregnancy. METHODS: We used murine models of normal, abortion-prone, and pseudopregnancy to characterize regulatory T cells and hormones by methods such as flow cytometry, molecular biology techniques, and chemiluminescence. Antigen specificity was studied in experiments in which animals were vaccinated with paternal antigens or adoptively transferred with regulatory T cells. To analyze regulatory T cell–mediated mechanisms, we used neutralizing antibodies against IL-10 or TGF-&bgr;. RESULTS: Regulatory T cells are activated by male antigens, and minor antigens are protected by linked immunosuppression. Our data exclude the possibility that regulatory T cell expansion during pregnancy is exclusively driven by hormonal changes. An increase in systemic regulatory T cell levels in pseudopregnant females after mating with vasectomized males but not after pseudopregnancy induced mechanically confirms generation of regulatory T cells specific for paternal antigens. As for the mechanisms, neutralizing IL-10 abrogates the protective effect of regulatory T cells, whereas blockage of TGF-&bgr; does not provide the same effect. CONCLUSION: Our data confirm that regulatory T cells act in an antigen-specific manner during pregnancy and strongly suggest that IL-10 is involved in regulatory T cell–mediated protection of the fetus. These data contribute to the knowledge of the basic mechanisms regulating immune tolerance during pregnancy, a major biologic question with important medical implications. LEVEL OF EVIDENCE: II

Protection from Abortion by Heme Oxygenase-1 Up-Regulation Is Associated with Increased Levels of Bag-1 and Neuropilin-1 at the Fetal-Maternal Interface

Tolerance mechanisms allowing pregnancy success resemble those involved in allograft acceptance. Heme oxygenase (HO) is a tissue-protective molecule, which allows graft acceptance and is known to have antiapoptotic effects on several cell types. We previously reported down-regulated levels of HO-1 and HO-2 in placenta from allopregnant mice undergoing abortion. In this study, we analyzed whether the up-regulation of HO-1 by cobalt-protoporphyrin (Co-PP) during implantation window can rescue mice from abortion. Induction of HO-1 by Co-PP treatment prevented fetal rejection, whereas the down-regulation of HOs by zinc-protoporphyrin application boosted abortion. The beneficial effect of HO-1 induction was not related to a local shift to Th2-profile or to a change in the NO system. Interestingly, the expression of the antiapoptotic/cytoprotective molecule Bag-1 as well as the levels of neuropilin-1, a novel marker for T regulatory cells, were up-regulated after Co-PP treatment. Our data strongly support a very important role for HO-1 in fetal allotolerance and suggest that HO-1 might be protective by up-regulating tissue protective molecules, i.e., Bag-1, and by activating T regulatory cells rather than by changing the local cytokine profile.

Classification of common variable immunodeficiencies using flow cytometry and a memory B-cell functionality assay.

BACKGROUND The population of patients with common variable immunodeficiency (CVID) comprises a heterogeneous group of patients with different causes of hypogammaglobulinemia predisposing to recurrent infections, higher incidence of autoimmunity, and malignancy. Although memory B cells (memBcs) are key players in humoral defense and their numbers are commonly reduced in these patients, their functionality is not part of any current classification. OBJECTIVE We established and validated a memBc enzyme-linked immunosorbent spot (ELISpot) assay that reveals the capacity of memBcs to develop into antibody-secreting cells and present an idea for a new classification based on this functional capacity. METHODS The memBc ELISpot assay, combined with flow cytometry, was applied to patients with confirmed CVID in comparison with age-matched healthy control subjects. RESULTS Ex vivo frequency of IgG-, IgM-, and IgA-secreting plasmablasts was significantly diminished by 27.2-, 2.4-, and 23.3-fold, respectively, compared with that seen in healthy control subjects. Moreover, in vitro differentiation of memBcs into antibody-secreting cells was 6.1-, 2.6-, and 3.7-fold significantly reduced for IgG-, IgM-, and IgA-secreting cells, respectively. Proliferation of memBcs correlates inversely to immunoglobulin-secreting capacity, suggesting compensatory hyperproliferation. Furthermore, patients with no serum IgA can still have a detectable IgA ELISpot assay result in vitro. Most importantly, the large heterogeneity of memBc function in patients with CVID homogenously grouped by means of fluorescence-activated cell sorting allowed additional subclassification based on memBc/plasmablast function. CONCLUSION These data suggest almost normal memBc/immunoglobulin-secreting plasmablast functionality in some patients if sufficient stimulatory signals are delivered, which might open up opportunities for new therapeutic approaches.

Mechanisms behind flare of renal lupus during murine pregnancy

The outcome of pregnancy in systemic lupus erythematosus is still controversial. The authors recently reported the disappearance of the manifestation of the skin disease but a diminished survival rate in lupus-prone animals undergoing several pregnancies. It was postulated that lupus-prone animals must have subclinical renal symptoms at an early age and that immune and hormonal changes during pregnancy exacerbate immune reactions in the kidneys, leading to a shortened life span. Here, the authors analysed changes at day 14 of pregnancy in lupus-prone LPR (MRL/lpr) mice and MRL controls regarding cytokines, regulatory T (Treg) cells and deposition of immunocomplexes. Worsened kidney function was observed during pregnancy, even in the absence of lupus signs. This was accompanied by renal inflammation and higher interferon-gamma and interleukin-10 levels. C3 and immunoglobulin G deposition was enhanced in kidney and placenta from lupus-prone pregnant animals. Pregnancy enhanced the levels of Treg cells in control animals but not in lupus-prone animals. As pregnancy-induced Treg cells were shown to be specific for paternal antigens it is not to be expected that these Treg cells can help to destroy autoreactive cells. The authors conclude that early subclinical kidney disease in lupus-prone animals exacerbates during pregnancy. Albeit obtained with an experimental animal model, their data are potentially of importance for lupus patients of reproductive age.