M. Eikmans

Calcineurin inhibitors affect B cell antibody responses indirectly by interfering with T cell help

In general, humoral immune responses depend critically upon T cell help. In transplantation, prevention or treatment of humoral rejection therefore require drugs that ideally inhibit both B cell and T helper cell activity. Here, we studied the effects of commonly used immunosuppressive drugs [tacrolimus, cyclosporin, mycophenolic acid (MPA) and rapamycin] on T cell helper activity and on T cell‐dependent B cell responses. T cells were activated polyclonally in the presence of immunosuppressive drugs in order to analyse the effect of these drugs on T cell proliferation, co‐stimulatory ligand expression and cytokines. The impact of immunosuppressive drugs on T cell‐dependent immunoglobulin production by B cells was addressed in T–B cell co‐cultures. All drugs affected T cell proliferation and attenuated T cell co‐stimulatory ligand (CD154 and CD278) expression when T cells were activated polyclonally. Tacrolimus, cyclosporin and rapamycin also attenuated B cell stimulatory cytokine mRNA levels in T cells. As a consequence, a decrease in immunoglobulin levels was observed in autologous T–B cell co‐cultures, where T cell help is essential for immunoglobulin production. In contrast, when pre‐activated T cells were used to stimulate autologous B cells, calcineurin inhibitors failed to inhibit B cell immunoglobulin production, whereas MPA and rapamycin did show inhibition. From these studies, it is evident that calcineurin inhibitors affect the humoral immune response by interfering with T helper signals, but not by targeting B cells directly. Furthermore, our studies support the necessity of intervening in T cell helper function to attenuate humoral responses.

Alternatively spliced isoforms of fibronectin in immune-mediated glomerulosclerosis: the role of TGFβ and IL-4

Fibronectin (FN) is the main extracellular matrix component in glomerulosclerotic lesions. There are different FN isoforms that result from alternative splicing at the EDA and EDB regions of FN mRNA. Increased inclusion of EDA and EDB, which can be elicited by TGFβ, may be conducive to the development of glomerulosclerosis (GS). TGFβ and IL‐4 have previously been shown to play a role in the development of GS. In this study, the mRNA splicing patterns for EDA+ and EDB+ fibronectin were investigated in vivo in various experimental sclerotic glomerulopathies, in vitro in rat mesangial cells (MC) that were stimulated by TGFβ or transfected with IL‐4, and in human kidney biopsies with GS from patients with various kidney diseases. Analysis of glomerular FN mRNA demonstrated inclusion of both ED regions in rats with anti‐Thy1 nephritis or chronic serum sickness and in mice with anti‐GBM glomerulonephritis. Inclusion of both the EDA and EDB regions was associated with glomerular TGFβ expression. In contrast, in mice with Th2‐mediated graft‐versus‐host disease, a model for lupus nephritis, the FN transcripts included neither the EDA nor the EDB region, and renal TGFβ expression was absent. Compared to normal MCs in culture, MCs transfected with IL‐4 produced lower amounts of FN and demonstrated less EDA inclusion, while MC that had been treated with TGFβ showed increased production of FN and more EDA inclusion. Renal biopsies from patients with renal diseases, except those taken from patients with lupus nephritis, showed higher TGFβ levels, higher FN levels, and more EDA inclusion than controls. TGFβ may be a key player in the development of GS by inducing local FN production and alternative splicing of FN mRNA. In lupus glomerulonephritis, in which the involvement of TGFβ in GS is less prominent, Th2 cytokines such as IL‐4 probably account for increased intrarenal collagen synthesis and subsequent FN accumulation from the circulation. In conclusion, neither alternative FN splicing, nor a high transcription level of TGFβ, appears to be a general prerequisite for the development of GS. Copyright

The immunomodulating effect of seminal plasma on T cells

Seminal plasma (SP) contains immunomodulatory factors that may contribute to the formation of a tolerogenic environment at the embryo implantation site. The main focus of this study was to investigate the influence of SP on female T cells in the presence and absence of antigen-presenting cells (APCs) in an in vitro model. Female PBMCs and T cells were incubated with SP from seminal fluid samples of known and variable sperm quality. The immediate effect of SP on the mRNA expression of CD25, IL-10, IFN-γ, and Foxp3 was measured. Furthermore, proliferative responses, cytokine production, and CD25 expression were determined. Exposure to SP leads to increased mRNA expression of CD25, IL-10, and Foxp3 in T cells. Induction of mRNA for IL-10 and CD25 was dependent on the presence of APCs. Both PBMCs and T cells exposed to SP showed a proliferative response and produced several cytokines. The proliferative effects of SP on T cells observed were independent of sperm quality parameters, cytokines or soluble HLA molecules in SP. Furthermore, the presence of SP induced a higher expression of CD25 on the membrane of CD4+ T cells. SP has a direct immunomodulatory effect on T cells, as reflected in a proliferative response and upregulation of Foxp3. The presence of APCs is needed to induce IL-10 and CD25 upregulation in T cells exposed to SP. In conclusion, SP has both a direct and an indirect effect mediated through APCs on T cells.

Preeclampsia in autologous and oocyte donation pregnancy: is there a different pathophysiology?

Oocyte donation (OD) is a specific method of artificial reproductive technology that is accompanied by a higher risk of preeclampsia during pregnancy. The pathophysiological mechanism underlying preeclampsia in OD pregnancies is thought to differ from preeclampsia in autologous pregnancies. As preeclampsia in autologous pregnancies is suggested to be associated with complement activation, we studied C4d deposition, circulating complement components and placental complement regulatory proteins in preeclamptic OD pregnancies. Women with uncomplicated and preeclamptic pregnancies after OD or spontaneous conception were selected. We stained the placentas for C4d, marker for complement activation, measured complement factors C1q, C3 and C4 in maternal sera and quantified the placental mRNA expression of complement regulatory proteins CD46, CD55 and CD59. A significantly (p < 0.03) higher incidence of C4d deposition was observed in placentas from women with preeclampsia compared with uncomplicated pregnancies, both OD and autologous. The level of complement factors in serum did not differ between the groups. Children born in the autologous preeclampsia group were significantly lower in birth weight (p < 10th percentile) compared with the preeclamptic OD group. In addition, the placental mRNA expression level of complement regulatory proteins was significantly lower in uncomplicated and preeclamptic OD compared with the autologous pregnancies. In line with autologous preeclampsia pregnancies, there is excessive activation of complement in preeclamptic OD pregnancies. However, in contrast to autologous pregnancies this is not associated with counterbalancing upregulation of complement regulatory proteins. Furthermore, C4d deposition in OD pregnancies is not related to the severity of preeclampsia, suggesting another trigger or regulatory mechanism of placental C4d deposition in preeclamptic OD pregnancies.

The seed to success: The role of seminal plasma in pregnancy

A lack of immunologic tolerance of the mother toward her child and in placentation can result in early or late pregnancy complications, including implantation failure, miscarriage, preeclampsia, and fetal growth restriction. Seminal plasma has the potential of influencing the maternal immune system for acceptance of the semi-allogeneic fetus. Here we elaborate on studies which provide evidence that an optimal balance of pro-inflammatory and immunomodulatory factors is necessary for the induction of immunologic tolerance and the process of implantation and placentation. Seminal plasma is a source of immunological mediators at conception, which can influence the function of maternal immune cells. Identifying the relevant factors in seminal plasma and the mechanisms by which they affect the maternal reproductive tract in relation to pregnancy outcome is a challenge for future research.

Lower frequency of the HLA-G UTR-4 haplotype in women with unexplained recurrent miscarriage

HLA-G expressed by trophoblasts at the fetal-maternal interface and its soluble form have immunomodulatory effects. HLA-G expression depends on the combination of DNA polymorphisms. We hypothesized that combinations of specific single nucleotide polymorphisms (SNPs) in the 3untranslated region (3UTR) of HLA-G play a role in unexplained recurrent miscarriage. In a case control design, 100 cases with at least three unexplained consecutive miscarriages prior to the 20th week of gestation were included. Cases were at time of the third miscarriage younger than 36 years, and they conceived all their pregnancies from the same partner. The control group included 89 women with an uneventful pregnancy. The association of HLA-G 3UTR SNPs and specific HLA-G haplotype with recurrent miscarriage was studied with logistic regression. Odds ratios (OR) and 95% confidence intervals (95% CI) were reported. Individual SNPs were not significantly associated with recurrent miscarriage after correction for multiple comparisons. However, the presence of the UTR-4 haplotype, which included +3003C, was significantly lower in women with recurrent miscarriage (OR 0.4, 95% CI 0.2-0.8, pu202f=u202f0.015). In conclusion, this is the first study to perform a comprehensive analysis of HLA-G SNPs and HLA-G haplotypes in a well-defined group of women with recurrent miscarriage and women with uneventful pregnancy. The UTR-4 haplotype was less frequently observed in women with recurrent miscarriage, suggesting an immunoregulatory role of this haplotype for continuation of the pregnancy without complications. Thus, association of HLA-G with recurrent miscarriage is not related to single polymorphisms in the 3UTR, but is rather dependent on haplotypes.