Maria C. Jenmalm

Decreased gut microbiota diversity, delayed Bacteroidetes colonisation and reduced Th1 responses in infants delivered by Caesarean section

Objective The early intestinal microbiota exerts important stimuli for immune development, and a reduced microbial exposure as well as caesarean section (CS) has been associated with the development of allergic disease. Here we address how microbiota development in infants is affected by mode of delivery, and relate differences in colonisation patterns to the maturation of a balanced Th1/Th2 immune response. Design The postnatal intestinal colonisation pattern was investigated in 24 infants, born vaginally (15) or by CS (nine). The intestinal microbiota were characterised using pyrosequencing of 16S rRNA genes at 1 week and 1, 3, 6, 12 and 24 months after birth. Venous blood levels of Th1- and Th2-associated chemokines were measured at 6, 12 and 24 months. Results Infants born through CS had lower total microbiota diversity during the first 2 years of life. CS delivered infants also had a lower abundance and diversity of the Bacteroidetes phylum and were less often colonised with the Bacteroidetes phylum. Infants born through CS had significantly lower levels of the Th1-associated chemokines CXCL10 and CXCL11 in blood. Conclusions CS was associated with a lower total microbial diversity, delayed colonisation of the Bacteroidetes phylum and reduced Th1 responses during the first 2 years of life.

Characterization of the CD200 Receptor Family in Mice and Humans and Their Interactions with CD200

CD200 (OX2) is a broadly distributed cell surface glycoprotein that interacts with a structurally related receptor (CD200R) expressed on rodent myeloid cells and is involved in regulation of macrophage function. We report the first characterization of human CD200R (hCD200R) and define its binding characteristics to hCD200. We also report the identification of a closely related gene to hCD200R, designated hCD200RLa, and four mouse CD200R-related genes (termed mCD200RLa-d). CD200, CD200R, and CD200R-related genes were closely linked in humans and mice, suggesting that these genes arose by gene duplication. The distributions of the receptor genes were determined by quantitative RT-PCR, and protein expression was confirmed by a set of novel mAbs. The distribution of mouse and human CD200R was similar, with strongest labeling of macrophages and neutrophils, but also other leukocytes, including monocytes, mast cells, and T lymphocytes. Two mCD200 receptor-like family members, designated mCD200RLa and mCD200RLb, were shown to pair with the activatory adaptor protein, DAP12, suggesting that these receptors would transmit strong activating signals in contrast to the apparent inhibitory signal delivered by triggering the CD200R. Despite substantial sequence homology with mCD200R, mCD200RLa and mCD200RLb did not bind mCD200, and presently have unknown ligands. The CD200 receptor gene family resembles the signal regulatory proteins and killer Ig-related receptors in having receptor family members with potential activatory and inhibitory functions that may play important roles in immune regulation and balance. Because manipulation of the CD200-CD200R interaction affects the outcome of rodent disease models, targeting of this pathway may have therapeutic utility.

The composition of the gut microbiota throughout life, with an emphasis on early life

Abstract The intestinal microbiota has become a relevant aspect of human health. Microbial colonization runs in parallel with immune system maturation and plays a role in intestinal physiology and regulation. Increasing evidence on early microbial contact suggest that human intestinal microbiota is seeded before birth. Maternal microbiota forms the first microbial inoculum, and from birth, the microbial diversity increases and converges toward an adult-like microbiota by the end of the first 3–5 years of life. Perinatal factors such as mode of delivery, diet, genetics, and intestinal mucin glycosylation all contribute to influence microbial colonization. Once established, the composition of the gut microbiota is relatively stable throughout adult life, but can be altered as a result of bacterial infections, antibiotic treatment, lifestyle, surgical, and a long-term change in diet. Shifts in this complex microbial system have been reported to increase the risk of disease. Therefore, an adequate establishment of microbiota and its maintenance throughout life would reduce the risk of disease in early and late life. This review discusses recent studies on the early colonization and factors influencing this process which impact on health.

Low gut microbiota diversity in early infancy precedes asthma at school age

Low total diversity of the gut microbiota during the first year of life is associated with allergic diseases in infancy, but little is known how early microbial diversity is related to allergic disease later in school age.

Altered early infant gut microbiota in children developing allergy up to 5 years of age.

Background Early colonization with bifidobacteria and lactobacilli is postulated to protect children from allergy, while Clostridium (C.) difficile colonization might be associated with allergic disease. Previous studies of infant gut microbiota in relation to subsequent allergy development have mostly employed culture‐dependent techniques, studied genera of bacteria and the follow‐up period was limited to 2 years.

Influence of early gut microbiota on the maturation of childhood mucosal and systemic immune responses

Introduction Among sensitized infants, those with high, as compared with low levels, of salivary secretory IgA (SIgA) are less likely to develop allergic symptoms. Also, early colonization with certain gut microbiota, e.g. Lactobacilli and Bifidobacterium species, might be associated with less allergy development. Although animal and in vitro studies emphasize the role of the commensal gut microbiota in the development of the immune system, the influence of the gut microbiota on immune development in infants is unclear.

Cytokines in breast milk from allergic and nonallergic mothers.

The allergy-preventing effect of breast-feeding remains controversial, possibly because of individual variations in the composition of the breast milk. The aim of this study was to investigate the concentrations of cytokines involved in allergic reactions and IgA antibody production in breast milk from allergic and nonallergic mothers. The cytokine concentrations were determined in colostrum and 1-mo milk samples from 24 mothers with, and 25 mothers without, atopic symptoms, using commercial ELISA kits. The immunosuppressive cytokine transforming growth factor-β was predominant and was detectable in all milk samples. IL-6 was detected in the majority of colostral and mature milk samples, whereas the other cytokines were less commonly detected. The concentrations of IL-6, IL-10, and transforming growth factor-β, which are all involved in IgA synthesis, correlated with each other and with total IgA concentrations in colostrum. The concentrations of IL-4 were higher in colostrum from allergic than nonallergic mothers, and similar trends were seen for IL-5 and IL-13. In conclusion, transforming growth factor-β and IL-6 were the predominant cytokines in human milk. The correlation between the concentrations of cytokines involved in IgA synthesis, i.e. IL-10, IL-6, and transforming growth factor-β, may explain the stimulatory effect on IgA production in breast-fed babies. Varying concentrations of IL-4, IL-5, and IL-13 may explain some of the controversy regarding the possible allergy-preventive effect of breast-feeding.

Macrophages at the Fetal–Maternal Interface Express Markers of Alternative Activation and Are Induced by M-CSF and IL-10

During pregnancy, the maternal immune system is challenged by the presence of the fetus, which must be tolerated despite being semiallogeneic. Uterine mucosal (or decidual) macrophages (Mϕ), one of the major leukocyte populations at the fetal–maternal interface, have been implicated in fetal tolerance, but information regarding their regulation is scarce. In this study, we investigated the role of several factors potentially involved in the differentiation and polarization of decidual Mϕ with an in vitro Mϕ differentiation model. By using flow cytometry, we showed that M-CSF and IL-10 were potent inducers of M2 (immunoregulatory) Mϕ markers expressed on human decidual Mϕ (CD14, CD163, CD206, CD209). In contrast, proinflammatory stimuli, and unexpectedly also the Th2-associated IL-4 and IL-13, induced different patterns of expression, indicating that a Th2-dominated environment is not required for decidual Mϕ polarization. M-CSF/IL-10–stimulated and decidual Mϕ also showed similar cytokine secretion patterns, with production of IL-10 as well as IL-6, TNF, and CCL4. Conversely, the proinflammatory, LPS/IFN-γ–stimulated Mϕ produced significantly higher levels of TNF and no IL-10. We also used a gene array with 420 Mϕ-related genes, of which 100 were previously reported to be regulated in a global gene expression profiling of decidual Mϕ, confirming that M-CSF/IL-10–induced Mϕ are closely related to decidual Mϕ. Taken together, our results consistently point to a central role for M-CSF and in particular IL-10 in the shaping of decidual Mϕ with regulatory properties. These cytokines may therefore play an important role in supporting the homeostatic and tolerant immune milieu required for a successful pregnancy.

Regulation of myeloid cell function through the CD200 receptor

Myeloid cells play pivotal roles in chronic inflammatory diseases through their broad proinflammatory, destructive, and remodeling capacities. CD200 is widely expressed on a variety of cell types, while the recently identified CD200R is expressed on myeloid cells and T cells. CD200 deletion in vivo results in myeloid cell dysregulation and enhanced susceptibility to autoimmune inflammation, suggesting that the CD200-CD200R interaction is involved in immune suppression. We demonstrate in this study that CD200R agonists suppress mouse and human myeloid cell function in vitro, and also define a dose relationship between receptor expression and cellular inhibition. IFN-γ- and IL-17-stimulated cytokine secretion from mouse peritoneal macrophages was inhibited by CD200R engagement. Inhibitory effects were not universal, as LPS-stimulated responses were unaffected. Inhibition of U937 cell cytokine production correlated with CD200R expression levels, and inhibition was only observed in low CD200R expressing cells, if the CD200R agonists were further cross-linked. Tetanus toxoid-induced human PBMC IL-5 and IL-13 secretion was inhibited by CD200R agonists. This inhibition was dependent upon cross-linking the CD200R on monocytes, but not on cross-linking the CD200R on CD4+ T cells. In all, we provide direct evidence that the CD200-CD200R interaction controls monocyte/macrophage function in both murine and human systems, further supporting the potential clinical application of CD200R agonists for the treatment of chronic inflammatory diseases.

FOXP3+ Regulatory T Cells and T Helper 1, T Helper 2, and T Helper 17 Cells in Human Early Pregnancy Decidua

In pregnancy, the decidua is infiltrated by leukocytes promoting fetal development without causing immunological rejection. Murine regulatory T (Treg) cells are known to be important immune regulators at this site. The aim of the study was to characterize the phenotype and origin of Treg cells and determine the quantitative relationship between Treg, T-helper type 1 (TH1), TH2, and TH17 cells in first-trimester human decidua. Blood and decidual CD4+ T cells from 18 healthy first-trimester pregnant women were analyzed for expression of Treg-cell markers (CD25, FOXP3, CD127, CTLA4, and human leukocyte antigen-DR [HLA-DR]), chemokine receptors (CCR4, CCR6, and CXCR3), and the proliferation antigen MKI67 by six-color flow cytometry. Treg cells were significantly enriched in decidua and displayed a more homogenous suppressive phenotype with more frequent expression of FOXP3, HLA-DR, and CTLA4 than in blood. More decidual Treg cells expressed MKI67, possibly explaining their enrichment at the fetal-maternal interface. Using chemokine receptor expression profiles of CCR4, CCR6, and CXCR3 as markers for TH1, TH2, and TH17 cells, we showed that TH17 cells were nearly absent in decidua, whereas TH2-cell frequencies were similar in blood and decidua. CCR6+ TH1 cells, reported to secrete high levels of interferon gamma (IFNG), were fewer, whereas the moderately IFNG-secreting CCR6− TH1 cells were more frequent in decidua compared with blood. Our results point toward local expansion of Treg cells and low occurrence of TH17 cells. Furthermore, local, moderate TH1 activity seems to be a part of normal early pregnancy, consistent with a mild inflammatory environment controlled by Treg cells.