12 research outputs found
Innate and adaptive stimulation of murine diverse NKT cells result in distinct cellular responses
Type II NKT Cells: An Elusive Population With Immunoregulatory Properties
Natural killer T (NKT) cells are unique unconventional T cells that are reactive to lipid antigens presented on the non-polymorphic major histocompatibility class (MHC) I-like molecule CD1d. They have characteristics of both innate and adaptive immune cells, and have potent immunoregulatory roles in tumor immunity, autoimmunity, and infectious diseases. Based on their T cell receptor (TCR) expression, NKT cells are divided into two subsets, type I NKT cells with an invariant TCRα-chain (Vα24 in humans, Vα14 in mice) and type II NKT cells with diverse TCRs. While type I NKT cells are well-studied, knowledge about type II NKT cells is still limited, and it is to date only possible to identify subsets of this population. However, recent advances have shown that both type I and type II NKT cells play important roles in many inflammatory situations, and can sometimes regulate the functions of each other. Type II NKT cells can be both protective and pathogenic. Here, we review current knowledge on type II NKT cells and their functions in different disease settings and how these cells can influence immunological outcomes
Age-associated changes in erythrocyte glutathione peroxidase activity: Correlation with total antioxidant potential
319-321Oxidative stress is believed to play a central role in aging and
age-associated diseases. It leads to oxidative changes in human red blood cells
(RBCs) in vivo and in vitro. In this study, we evaluated the
oxidative damage to the erythrocytes during aging in the humans using RBC as a
model, by measuring the cytosolic antioxidant enzyme glutathione peroxidase
(GPx) activity. GPx activity was found to be significantly decreased as a
function of human age and positively correlated with total antioxidant
capacity, while negatively correlated with SOD activity. Thus, results of the
present study showed involvement of oxidative stress as one of the risk
factors, which can initiate and/or promote human aging
Commensal bacteria induce a barrier protective response to prevent sensitization to food allergens
Environmentally-induced alterations in the commensal microbiome have been implicated in
the increasing prevalence of food allergy. We found that antibiotic treatment of neonatal
mice leads to reduced proportions of regulatory T cells (Tregs) in the colonic lamina
propria(LP), impaired production of intestinal IgA, and elevated peanut (PN) specific
IgE/IgG1 in response to sensitization. Selective colonization of gnotobiotic mice linked the
Treg/IgA inducing capacity to a consortium of bacteria within the Clostridia class.
Introduction of either a conventional SPF microbiota or a mixture of Clostridia strains to
antibiotic-treated mice restored the Treg and IgA compartments and blocked the induction
of a food allergic response. Clostridia colonized gnotobiotic mice displayed increased
expression of IL-23 and IL-22 in the colonic LP compartment and the induction of
anti-microbial REG3β expression in the epithelium. Collectively, these results suggest that
the maintenance of oral tolerance to dietary antigens relies on bacterial populations that
induce a barrier protective response, which includes activation of the IL-23/IL22 axis and
the expansion of intestinal Tregs and IgA secreting B cells. Our findings hold promise for
the development of approaches to prevent or treat food allergy based on modulation of the
composition of intestinal microbiota
MATE transport of the E-coli-derived genotoxin colibactin
International audienceVarious forms of cancer have been linked to the carcinogenic activities of microorganisms(1-3). The virulent gene island polyketide synthase (pks) produces the secondary metabolite colibactin, a genotoxic molecule(s) causing double-stranded DNA breaks(4) and enhanced colorectal cancer development(5,6). Colibactin biosynthesis involves a prodrug resistance strategy where an N-terminal prodrug scaffold (precolibactin) is assembled, transported into the periplasm and cleaved to release the mature product(7-10). Here, we show that ClbM, a multidrug and toxic compound extrusion (MATE) transporter, is a key component involved in colibactin activity and transport. Disruption of clbM attenuated pks+ E. coli-induced DNA damage in vitro and significantly decreased the DNA damage response in gnotobiotic Il10(-/-) mice. Colonization experiments performed in mice or zebrafish animal models indicate that clbM is not implicated in E. coli niche establishment. The X-ray structure of ClbM shows a structural motif common to the recently described MATE family. The 12-transmembrane ClbM is characterized as a cation-coupled antiporter, and residues important to the cation-binding site are identified. Our data identify ClbM as a precolibactin transporter and provide the first structure of a MATE transporter with a defined and specific biological function
ClbS Is a Cyclopropane Hydrolase That Confers Colibactin Resistance
Certain commensal Escherichia coli contain the <i>clb</i> biosynthetic gene cluster that
codes for small molecule prodrugs known as precolibactins. Precolibactins
are converted to colibactins by <i>N</i>-deacylation; the
latter are postulated to be genotoxic and to contribute to colorectal
cancer formation. Though advances toward elucidating (pre)Âcolibactin
biosynthesis have been made, the functions and mechanisms of several <i>clb</i> gene products remain poorly understood. Here we report
the 2.1 Ă… X-ray structure and molecular function of ClbS, a gene
product that confers resistance to colibactin toxicity in host bacteria
and which has been shown to be important for bacterial viability.
The structure harbors a potential colibactin binding site and shares
similarity to known hydrolases. <i>In vitro</i> studies
using a synthetic colibactin analog and ClbS or an active site residue
mutant reveal cyclopropane hydrolase activity that converts the electrophilic
cyclopropane of the colibactins into an innocuous hydrolysis product.
As the cyclopropane has been shown to be essential for genotoxic effects <i>in vitro</i>, this ClbS-catalyzed ring-opening provides a means
for the bacteria to circumvent self-induced genotoxicity. Our study
provides a molecular-level view of the first reported cyclopropane
hydrolase and support for a specific mechanistic role of this enzyme
in colibactin resistance
Commensal bacteria protect against food allergen sensitization.
Environmentally induced alterations in the commensal microbiota have been implicated in the increasing prevalence of food allergy. We show here that sensitization to a food allergen is increased in mice that have been treated with antibiotics or are devoid of a commensal microbiota. By selectively colonizing gnotobiotic mice, we demonstrate that the allergy-protective capacity is conferred by a Clostridia-containing microbiota. Microarray analysis of intestinal epithelial cells from gnotobiotic mice revealed a previously unidentified mechanism by which Clostridia regulate innate lymphoid cell function and intestinal epithelial permeability to protect against allergen sensitization. Our findings will inform the development of novel approaches to prevent or treat food allergy based on modulating the composition of the intestinal microbiota
Splicing regulator SRSF1-3 that controls somatic hypermutation of IgV genes interacts with topoisomerase 1 and AID
Highly protective antimalarial antibodies via precision library generation and yeast display screening
The monoclonal antibody CIS43 targets the Plasmodium falciparum circumsporozoite protein (PfCSP) and prevents malaria infection in humans for up to 9 mo following a single intravenous administration. To enhance the potency and clinical utility of CIS43, we used iterative site-saturation mutagenesis and DNA shuffling to screen precise gene-variant yeast display libraries for improved PfCSP antigen recognition. We identified several mutations that improved recognition, predominately in framework regions, and combined these to produce a panel of antibody variants. The most improved antibody, CIS43_Var10, had three mutations and showed approximately sixfold enhanced protective potency in vivo compared to CIS43. Co-crystal and cryo-electron microscopy structures of CIS43_Var10 with the peptide epitope or with PfCSP, respectively, revealed functional roles for each of these mutations. The unbiased site-directed mutagenesis and screening pipeline described here represent a powerful approach to enhance protective potency and to enable broader clinical use of antimalarial antibodies.</jats:p