Transferrin receptor expression and the regulation of placental iron uptake

Placental transferrin receptors, located at the apical side of syncytiotrophoblast, mediate placental iron uptake. Regulation of transferrin receptors on the fetal-maternal exchange area could be a major determinant in the regulation of trans-placental iron transport. Transferrin receptor expression in cultured human term cytotrophoblasts is on a much lower level than in choriocarcinoma cells, with a higher proportion of receptors located on the cell surface. Differentiation of cells, either due to longer culture periods or to 8-bromo-cAMP treatment does not lead to an increase of transferrin receptor expression. In vitro, the level of expression is largely regulated by the cellular density in the culture dishes. Low cellular occupancy of the dish leads to a high level of transferrin receptors. Treatment with iron-sources results in a down regulation of transferrin receptors. Thus, though the level of transferrin receptors in cultured normal trophoblast is at a constant level, unaffected by differentiation, high levels of maternal transferrin-iron availability can lead to a decrease in placental iron uptake. This feed-back mechanism makes placental iron uptake independent of maternal iron stores

Wnt target genes identified by DNA microarrays in immature CD34+ thymocytes regulate proliferation and cell adhesion

The thymus is seeded by very small numbers of progenitor cells that undergo massive proliferation before differentiation and rearrangement of TCR genes occurs. Various signals mediate proliferation and differentiation of these cells, including Wnt signals. Wnt signals induce the interaction of the cytoplasmic cofactor beta-catenin with nuclear T cell factor (TCF) transcription factors. We identified target genes of the Wnt/beta-catenin/TCF pathway in the most immature (CD4-CD8-CD34+) thymocytes using Affymetrix DNA microarrays in combination with three different functional assays for in vitro induction of Wnt signaling. A relatively small number (approximately 30) of genes changed expression, including several proliferation-inducing transcription factors such as c-fos and c-jun, protein phosphatases, and adhesion molecules, but no genes involved in differentiation to mature T cell stages. The adhesion molecules likely confine the proliferating immature thymocytes to the appropriate anatomical sites in the thymus. For several of these target genes, we validated that they are true Wnt/beta-catenin/TCF target genes using real-time quantitative PCR and reporter gene assays. The same core set of genes was repressed in Tcf-1-null mice, explaining the block in early thymocyte development in these mice. In conclusion, Wnt signals mediate proliferation and cell adhesion, but not differentiation of the immature thymic progenitor pool

Canonical Wnt signaling negatively modulates regulatory T cell function

Foxp3 is crucial for both the development and function of regulatory T (Treg) cells; however, the posttranslational mechanisms regulating Foxp3 transcriptional output remain poorly defined. Here, we demonstrate that Tcell factor 1 (TCF1) and Foxp3 associates in Treg cells and that active Wnt signaling disrupts Foxp3 transcriptional activity. A global chromatin immunoprecipitation sequencing comparison in Treg cells revealed considerable overlap between Foxp3 and Wnt target genes. The activation of Wnt signaling reduced Treg-mediated suppression both invitro and invivo, whereas disruption of Wnt signaling in Treg cells enhanced their suppressive capacity. The activation of effector Tcells increased Wnt3a production, and Wnt3a levels were found to be greatly increased in mononuclear cells isolated from synovial fluid versus peripheral blood of arthritis patients. We propose a model in which Wnt produced under inflammatory conditions represses Treg cell function, allowing a productive immune response, but, if uncontrolled, could lead to the development of autoimmunity

Immunogenicity and efficacy of one and two doses of Ad26.COV2.S COVID vaccine in adult and aged NHP

Safe and effective coronavirus disease-19 (COVID-19) vaccines are urgently needed to control the ongoing pandemic. While single-dose vaccine regimens would provide multiple advantages, two doses may improve the magnitude and durability of immunity and protective efficacy. We assessed one-and two-dose regimens of the Ad26.COV2.S vaccine candidate in adult and aged nonhuman primates (NHPs). A two-dose Ad26.COV2.S regimen induced higher peak binding and neutralizing antibody responses compared with a single dose. In one-dose regimens, neutralizing antibody responses were stable for at least 14 wk, providing an early indication of durability. Ad26.COV2.S induced humoral immunity and T helper cell (Th cell) 1-skewed cellular responses in aged NHPs that were comparable to those in adult animals. Aged Ad26.COV2.S-vaccinated animals challenged 3 mo after dose 1 with a SARS-CoV-2 spike G614 variant showed near complete lower and substantial upper respiratory tract protection for both regimens. Neutralization of variants of concern by NHP sera was reduced for B.1.351 lineages while maintained for the B.1.1.7 lineage independent of Ad26.COV2.S vaccine regimen.Molecular basis of virus replication, viral pathogenesis and antiviral strategie

Differential mRNA expression and production of interleukin-4 and interferon-gamma in stimulated peripheral blood mononuclear cells of house-dust mite-allergic patients

Summary : Optimal culture conditions were established for the analysis of interleukin-4 (IL-4) and interfe-ron-gamma (IFN- ) mRNA expression and protein production, as well as proliferative capacity of peripheral blood mononuclear cells (PBMC). These culture conditions permitted the analysis of differences in the responses of house-dust mite (HDM) allergic patients and healthy controls after polyclonal and allergen-specific stimulation. Proliferative responses were optimal when PBMC were cultured in RPMI, whereas for studying mRNA expression by RT-PCR and protein production by ELISA, PBMC should be stimulated in Yssels’s medium. Blood holding period influenced the cytokine mRNA expression and proliferative capacity of primarily the unstimulated cells. It is thus crucial to isolate PBMC as soon as possible, and in any event no later than 7 hours after blood collection. Proliferative responses to Dermatophagoides pteronyssinus-extract were observed in HDM allergic patients (mean stimulation index (SI) = 5.3 ± 0.75), but not in non-allergic subjects (mean SI = 2.3 ± 0.21). After D. pte-ronyssinus-specific stimulation, IL-4 mRNA expression was significantly (p = 0.03) increased in HDM-allergic subjects compared to non-allergic subjects. No significant differences were found in IFN- mRNA expression between HDM-allergic and non-allergic subjects. Both IFN- (p = 0.04) and IL-4 (p = 0.06) protein production were increased after D. pteronyssinus-specific stimulation in HDM-allergic subjects compared to non-allergic subjects. Our data suggest activation of both Th1 and Th2-like cells, as well as CD8 T cells in allergic patients. Furthermore, analysis of possible functional differences in PBMC between allergic and non-allergic patients, necessitates polyclonal and allergen-specific stimulation of PBMC. Moreover, proliferative responses as well as cytokine mRNA expression and protein production should be studied under optimal culture conditions to highlight the often subtle differences. Keywords : cytokine expression and production, allergy, proliferative response

T cell subsets and cytokines in allergic and non-allergic children. I. Analysis of IL-4, IFN-? and IL-13 mRNA expression and protein production

Interleukin 4 (IL-4) and IL-13 are key cytokines inducing switching to immunoglobulin E (IgE), whereas interferon (IFN-) acts inhibitory on this process. We analysed whether differences existed in IL-4, IFN- and IL-13 mRNA expression and protein production between T cells of children with allergic and non-allergic asthma, atopic dermatitis and healthy control children. IL-4 mRNA expression was increased in stimulated T cells of children with allergic asthma and atopic dermatitis, but not in those with non-allergic asthma as compared with healthy controls. Thus the increase in IL-4 expression can be considered as an underlying mechanism of the allergic disease process and not so much of the asthmatic state of the children. In unstimulated T cells of children with atopic dermatitis increased IFN- mRNA expression with a reduced IFN- protein production was found, indicating a post-translational defect in IFN-. Differences in Il-13 expression between the groups were not significant, but IL-13 was significantly correlated with the height of the radio-allergo-sorbent test (RAST) class and with the severity scoring of atopic dermatitis (SCORAD) index. This indicates the clinical relevance of IL-13 for the degree of allergen-specific sensitization and severity of atopic dermatitis. In conclusion, the imbalance in IL-4 and IFN- secretion in patients with atopic dermatitis may reflect general T cell activation in the presence of an intrinsic defect of IFN- secretion. Author Keywords: allergy; children; IL-4; IFN-; IL-1

T cell subsets and cytokines in allergic and non-allergic children. II. Analysis of IL-5 and IL-10 mRNA expression and protein production

Interleukin 5 (IL-5) has an enhancing effect on IL-4 induced immunoglobulin E (IgE) synthesis. Furthermore, IL-5 plays an important role in the differentiation, recruitment, activation and survival of eosinophils, IL-10 has a downmodulating effect on interferon (IFN-) production and can exert strong anti-inflammatory activities. Therefore, we analysed whether differences were present in IL-5 and IL-10 mRNA expression and protein production between T cells of children with allergic and non-allergic asthma, atopic dermatitis and healthy control children. We demonstrated significant increases in IL-5 mRNA expression and protein production in different T cell fractions of children with allergic and non-allergic asthma and children with atopic dermatitis as compared to healthy controls. This indicates that IL-5 is not only involved in allergy, but also plays a role in the inflammatory process of non-allergic asthma. Interestingly, IL-10 mRNA expression by purified T cells of children with allergic and non-allergic asthma and children with atopic dermatitis was strongly decreased as compared with that of healthy controls. In the peripheral blood mononuclear cell (PBMC) fraction, IL-10 mRNA expression was comparable between the four groups. We hypothesize that this decreased T cell derived IL-10 expression results in a lack of immunosuppression of the inflammatory process in these diseases. However, a role of monocyte derived IL-10 cannot be ruled out. Author Keywords: allergy; children; IL-5; IL-1

Development of immune functions related to allergic mechanisms in young children

The newborn immune system differs quantitatively and functionally from that of adults. Development of the immune system has important implications for childhood diseases. The immaturity of the immune system in the first years of life may contribute to failure of tolerance induction and in the development of allergic disease. T cell function is diminished, especially the capacity to produce cytokines; production of interferon (IFN)-gamma, and IL-4 is strongly reduced. IFN-gamma has been found to be even lower in cord blood of newborns with a family history of atopy. Differences in other cell types (natural killer cells, antigen-presenting cells, and B cells) could also play a role in the development of allergic disease. Current data suggest that irregularities in IgE synthesis, helper T cell subsets (Th1, Th2, CD45RA, and CD45RO), cytokines (IL-4, IFN-gamma), and possibly other cell types may play a role in the development of allergy in childhood. Moreover, the role of cell surface molecules, like co-stimulatory molecules (CD28, CD40L), activation markers (CD25), and adhesion molecules (LFA-1/ICAM-1, VLA-4/ VCAM-1) is also discussed. These variables are modulated by genetic (relevant loci are identified on chromosome 5q, 11q, and 14) and environmental forces (allergen exposure, viral infections, and smoke). The low sensitivity of current predictive factors for the development of allergic diseases, such as cord blood IgE levels, improves in combination with family history and by measurement of in vitro responses of lymphocytes and skin reactivity to allergens. New therapeutic approaches are being considered on the basis of our current understanding of the immunopathology of allergic disease, for instance cytokine therapy and vaccination with tolerizing doses of allergen or peptides