A Decreased Frequency of Regulatory T Cells in Patients with Common Variable Immunodeficiency

Introduction

Common variable immunodeficiency disorder (CVID) is a heterogeneous syndrome, characterized by deficient antibody production and recurrent bacterial infections in addition abnormalities in T cells. CD4⁺CD25^high regulatory T cells (Treg) are essential modulators of immune responses, including down-modulation of immune response to pathogens, allergens, cancer cells and self-antigens.

Objective

In this study we set out to investigate the frequency of Treg cells in CVID patients and correlate with their immune activation status.

Materials and Methods

Sixteen patients (6 males and 10 females) with CVID who had been treated with regular intravenous immunoglobulin and 14 controls were enrolled. Quantitative analyses of peripheral blood mononuclear cells (PBMC) were performed by multiparametric flow cytometry using the following cell markers: CD38, HLA-DR, CCR5 (immune activation); CD4, CD25, FOXP3, CD127, and OX40 (Treg cells); Ki-67 and IFN-γ (intracellular cytokine).

Results

A significantly lower proportion of CD4⁺CD25^highFOXP3 T cells was observed in CVID patients compared with healthy controls (P<0.05). In addition to a higher proportion of CD8⁺ T cells from CVID patients expressing the activation markers, CD38⁺ and HLA-DR⁺ (P<0.05), we observed no significant correlation between Tregs and immune activation.

Conclusion

Our results demonstrate that a reduction in Treg cells could have impaired immune function in CVID patients.     

Identification of noncytotoxic and IL-10-producing CD8+AT2R+ T cell population in response to ischemic heart injury

Emerging evidence suggests a cardioprotective role of the angiotensin AT2R, albeit the underlying cellular mechanisms are not well understood. We aimed in this article to elucidate a potential role of cardiac angiotensin AT2R in regulating cellular immune response to ischemic heart injury. Seven days after myocardial infarction in rats, double-immunofluorescence staining showed that AT2R was detected in a fraction of CD8(+) T cells infiltrating in the peri-infarct myocardium. We developed a method that allowed the isolation of myocardial infiltrating CD8(+)AT2R(+) T cells using modified MACS, and further characterization and purification with flow cytometry. Although the CD8(+)AT2R(-) T cells exhibited potent cytotoxicity to both adult and fetal cardiomyocytes (CMs), the CD8(+)AT2R(+) T cells were noncytotoxic to these CMs. The CD8(+)AT2R(+) T cells were characterized by upregulated IL-10 and downregulated IL-2 and INF-γ expression when compared with CD8(+)AT2R(-) T cells. We further showed that IL-10 gene expression was enhanced in CD8(+) T cells on in vitro AT2R stimulation. Importantly, in vivo AT2R activation engendered an increment of CD8(+)AT2R(+) T cells and IL-10 production in the ischemic myocardium. In addition, intramyocardial transplantation of CD8(+)AT2R(+) T cells (versus CD8(+)AT2R(-)) led to reduced ischemic heart injury. Moreover, the CD8(+)AT2R(+) T cell population was also demonstrated in human peripheral blood. Thus, we have defined the cardioprotective CD8(+)AT2R(+) T cell population, which increases during ischemic heart injury and contributes to maintaining CM viability and providing IL-10, hence revealing an AT2R-mediated cellular mechanism in modulating adaptive immune response in the heart.     

Distinct roles of jasmonates and aldehydes in plant-defense responses

Background

Many inducible plant-defense responses are activated by jasmonates (JAs), C₆-aldehydes, and their corresponding derivatives, produced by the two main competing branches of the oxylipin pathway, the allene oxide synthase (AOS) and hydroperoxide lyase (HPL) branches, respectively. In addition to competition for substrates, these branch-pathway-derived metabolites have substantial overlap in regulation of gene expression. Past experiments to define the role of C₆-aldehydes in plant defense responses were biased towards the exogenous application of the synthetic metabolites or the use of genetic manipulation of HPL expression levels in plant genotypes with intact ability to produce the competing AOS-derived metabolites. To uncouple the roles of the C₆-aldehydes and jasmonates in mediating direct and indirect plant-defense responses, we generated Arabidopsis genotypes lacking either one or both of these metabolites. These genotypes were subsequently challenged with a phloem-feeding insect (aphids: Myzus persicae), an insect herbivore (leafminers: Liriomyza trifolii), and two different necrotrophic fungal pathogens (Botrytis cinerea and Alternaria brassicicola). We also characterized the volatiles emitted by these plants upon aphid infestation or mechanical wounding and identified hexenyl acetate as the predominant compound in these volatile blends. Subsequently, we examined the signaling role of this compound in attracting the parasitoid wasp (Aphidius colemani), a natural enemy of aphids.

Principal Findings

This study conclusively establishes that jasmonates and C₆-aldehydes play distinct roles in plant defense responses. The jasmonates are indispensable metabolites in mediating the activation of direct plant-defense responses, whereas the C₆-aldehyes are not. On the other hand, hexenyl acetate, an acetylated C₆-aldehyde, is the predominant wound-inducible volatile signal that mediates indirect defense responses by directing tritrophic (plant-herbivore-natural enemy) interactions.

Significance

The data suggest that jasmonates and hexenyl acetate play distinct roles in mediating direct and indirect plant-defense responses. The potential advantage of this “division of labor” is to ensure the most effective defense strategy that minimizes incurred damages at a reduced metabolic cost.     

Rearing of Fabrea salina Henneguy (Ciliophora, Heterotrichida) with three unicellular feeds

The growth rate of the ciliate Fabrea salina was studied in batch cultures in the presence of three feeds, tested separately from each other: the Prymnesiophyceae, Isochrysis galbana obtained from pure culture, the Chlorophyceae Dunaliella salina, and the commercially available yeast Saccharomyces cerevisiae. F. salina, and D. salina were harvested below the surface from the first evaporation pond and the crystallizer pond, respectively in multi-pond salterns (Sfax, Tunisia). The highest density of Fabrea was recorded with I. galbana (26 ind ml(-1)). However, the greatest length (243 microm) was recorded with Fabrea fed with D. salina. The lowest density, length and biovolume values were recorded with Fabrea fed with S. cerevisiae. The ANOVA test showed that density (F=18, d.f.=57), length (F=33, d.f.=57), and biovolume (F=19, d.f.=57) of Fabrea fed with yeast were significantly different (p<0.001) from those when Fabrea was fed with D. salina and I. galbana. The ciliate Fabrea encountered in the Sfax saltern (Tunisia) might be a valuable food source for Tunisian marine fish hatcheries.     

Autophosphorylation and subcellular localization dynamics of a salt- and water deficit-induced calcium-dependent protein kinase from ice plant

A salinity and dehydration stress-responsive calcium-dependent protein kinase (CDPK) was isolated from the common ice plant (Mesembryanthemum crystallinum; McCPK1). McCPK1 undergoes myristoylation, but not palmitoylation in vitro. Removal of the N-terminal myristate acceptor site partially reduced McCPK1 plasma membrane (PM) localization as determined by transient expression of green fluorescent protein fusions in microprojectile-bombarded cells. Removal of the N-terminal domain (amino acids 1-70) completely abolished PM localization, suggesting that myristoylation and possibly the N-terminal domain contribute to membrane association of the kinase. The recombinant, Escherichia coli-expressed, full-length McCPK1 protein was catalytically active in a calcium-dependent manner (K0.5 = 0.15 microm). Autophosphorylation of recombinant McCPK1 was observed in vitro on at least two different Ser residues, with the location of two sites being mapped to Ser-62 and Ser-420. An Ala substitution at the Ser-62 or Ser-420 autophosphorylation site resulted in a slight increase in kinase activity relative to wild-type McCPK1 against a histone H1 substrate. In contrast, Ala substitutions at both sites resulted in a dramatic decrease in kinase activity relative to wild-type McCPK1 using histone H1 as substrate. McCPK1 undergoes a reversible change in subcellular localization from the PM to the nucleus, endoplasmic reticulum, and actin microfilaments of the cytoskeleton in response to reductions in humidity, as determined by transient expression of McCPK1-green fluorescent protein fusions in microprojectile-bombarded cells and confirmed by subcellular fractionation and western-blot analysis of 6x His-tagged McCPK1.     

Aerial surveys give new estimates for orangutans in Sabah, Malaysia

Great apes are threatened with extinction, but precise information about the distribution and size of most populations is currently lacking. We conducted orangutan nest counts in the Malaysian state of Sabah (North Borneo), using a combination of ground and helicopter surveys, and provided a way to estimate the current distribution and size of the populations living throughout the entire state. We show that the number of nests detected during aerial surveys is directly related to the estimated true animal density and that a helicopter is an efficient tool to provide robust estimates of orangutan numbers. Our results reveal that with a total estimated population size of about 11,000 individuals, Sabah is one of the main strongholds for orangutans in North Borneo. More than 60% of orangutans living in the state occur outside protected areas, in production forests that have been through several rounds of logging extraction and are still exploited for timber. The role of exploited forests clearly merits further investigation for orangutan conservation in Sabah.     

Protein kinase A-dependent phosphorylation of Lutheran/basal cell adhesion molecule glycoprotein regulates cell adhesion to laminin alpha5

Lutheran (Lu) blood group and basal cell adhesion molecule (B-CAM) antigens reside on two glycoprotein (gp) isoforms Lu and Lu(v13) that belong to the Ig superfamily and differ only by the size of their cytoplasmic tail. Lu/B-CAM gps have been recognized as laminin alpha5 receptors on red blood cells and epithelial cells in multiple tissues. It has been shown that sickle red cells exhibit enhanced adhesion to laminin alpha5 when intracellular cAMP is up-regulated by physiological stimuli such as epinephrine and that this signaling pathway is protein kinase A- and Lu/B-CAM-dependent. In this study, we analyzed the relationship between the phosphorylation status of Lu/B-CAM gps and their adhesion function to laminin alpha5. We showed that Lu isoform was phosphorylated in sickle red cells as well as in erythroleukemic K562 and epithelial Madin-Darby canine kidney cells and that this phosphorylation is enhanced by different stimuli of the PKA pathway. Lu gp is phosphorylated by glycogen synthase kinase 3 beta, casein kinase II, and PKA at serines 596, 598, and 621, respectively. Alanine substitutions of serines 596 and 598 abolished phosphorylation by glycogen synthase kinase 3 beta and casein kinase II, respectively, but had no effect on adhesion of K562 cells to laminin under flow conditions. Conversely, mutation of serine 621 prevented phosphorylation by PKA and dramatically reduced cell adhesion. Furthermore, stimulation of K562 cells by epinephrine increased Lu gp phosphorylation by PKA and enhanced adhesion to laminin. It is postulated that modulation of the phosphorylation state of Lu gp might be a critical factor for the sickle red cells adhesiveness to laminin alpha5 in sickle cell disease.     

Xylella fastidiosa Does Not Occur in Lebanon

Xylella fastidiosa has been reported as responsible for a devastating disease on olive trees in Apulia region (south‐eastern Italy), characterized by a quick decline syndrome. In Lebanon, the pathogen was recently associated with leaf scorch symptoms on oleander, and reports on leaf scorch and dieback of olive trees branches by technicians and farmers have shown an increasing trend in the main agricultural areas. To assess the occurrence and distribution of the pathogen in Lebanon, samples of twigs from olive trees (82), olive seedlings (26), grapevine (30), oleander (32) and ornamentals imported from Italy (48) were analysed by isolation on four agarized media, serological techniques (ELISA and DTBIA) using Xylella fastidiosa‐specific antibodies and by PCR, using three specific sets of primers. Results unequivocally demonstrated that all the collected samples were free from the pathogen. As well, both detection protocols and attempts at isolating the pathogen on agarized media demonstrated that oleander samples gathered from American University campus in Beirut, where X. fastidiosa was previously reported, were not infected. Nevertheless, continuous monitoring and rigorous control measures of propagative materials are necessary to prevent the introduction of Xylella fastidiosa in Lebanon.     

JAGGED1 and delta1 differentially regulate the outcome of experimental autoimmune encephalomyelitis

Notch signaling plays an important role during T cell development in the thymus and in T cell activation but the role of Notch in autoimmunity is not clear. We investigated the role of Jagged1 and Delta1 in experimental autoimmune encephalomyelitis. During experimental autoimmune encephalomyelitis, Delta1 expression is up-regulated on dendritic cells and B cells after priming while Jagged1 is up-regulated only on dendritic cells. Administration of anti-Jagged1 Ab exacerbated clinical disease while that of anti-Delta1 Ab reduced the severity of the clinical disease. In contrast, administration of Jagged1-Fc protected from disease, that of Delta1-Fc exacerbated disease. Treatment with Jagged1-Fc was associated with increased IL-10-producing Ag-specific cells in the CNS, while anti-Jagged1 decreased the frequency of IL-10-producing cells. Treatment with Delta1-Fc increased Th1 cells in the CNS, while anti-Delta-1 decreased the frequency of Th1 cells. Manipulation of Delta1 or Jagged1 had no effect on the frequency of Th17 cells or FoxP3(+) cells. Moreover, Jagged1 may play a role in CNS homeostasis because murine astrocytes specifically express Jagged1 that is up-regulated by TGF-beta, whereas IFN-gamma, TNF-alpha, and IL-17 decrease Jagged1 expression. Our study provides novel data about differential roles of Notch ligands in regulating inflammation in the periphery as well as in the CNS.