Environmental and T cell-intrinsic factors limit the expansion of neonatal follicular T helper cells but may be circumvented by specific adjuvants.

Follicular Th (T(FH)) cells have emerged as a new Th subset providing help to B cells and supporting their differentiation into long-lived plasma cells or memory B cells. Their differentiation had not yet been investigated following neonatal immunization, which elicits delayed and limited germinal center (GC) responses. We demonstrate that neonatal immunization induces CXCR5(high)PD-1(high) CD4(+) T(FH) cells that exhibit T(FH) features (including Batf, Bcl6, c-Maf, ICOS, and IL-21 expression) and are able to migrate into the GCs. However, neonatal T(FH) cells fail to expand and to acquire a full-blown GC T(FH) phenotype, as reflected by a higher ratio of GC T(FH)/non-GC CD4(+) T cells in immunized adults than neonates (3.8 × 10(-3) versus 2.2 × 10(-3), p = 0.01). Following the adoptive transfer of naive adult OT-II CD4(+) T cells, OT-II T(FH) cells expand in the vaccine-draining lymph nodes of immunized adult but not infant recipients, whereas naive 2-wk-old CD4(+) OT-II cells failed to expand in adult hosts, reflecting the influence of both environmental and T cell-intrinsic factors. Postponing immunization to later in life increases the number of T(FH) cells in a stepwise manner, in direct correlation with the numbers of GC B cells and plasma cells elicited. Remarkably, adjuvantation with CpG oligonucleotides markedly increased GC T(FH) and GC B cell neonatal responses, up to adult levels. To our knowledge, this is the first demonstration that the T(FH) cell development limits early life GC responses and that adjuvants/delivery systems supporting T(FH) differentiation may restore adultlike early life GC B cell responses.

Des sciences sourdes et une justice aveugle

La présente contribution a pour but d'explorer les défis soulevés par l'utilisation d'indices scientifiques au procès pénal et d'identifier les pièges tendus à une communication efficace entre le scientifique et son mandant judiciaire.

Contribution of isotope ratio mass spectrometry to the investigation of improvised explosives: isotopic study of black powders ans ammonium nitrates

The establishment of legislative rules about explosives in the eighties has reduced the illicit use of military and civilian explosives. However, bomb-makers have rapidly taken advantage of substances easily accessible and intended for licit uses to produce their own explosives. This change in strategy has given rise to an increase of improvised explosive charges, which is moreover assisted by the ease of implementation of the recipes, widely available through open sources. While the nature of the explosive charges has evolved, instrumental methods currently used in routine, although more sensitive than before, have a limited power of discrimination and allow mostly the determination of the chemical nature of the substance. Isotope ratio mass spectrometry (IRMS) has been applied to a wide range of forensic materials. Conclusions drawn from the majority of the studies stress its high power of discrimination. Preliminary studies conducted so far on the isotopic analysis of intact explosives (pre-blast) have shown that samples with the same chemical composition and coming from different sources could be differentiated. The measurement of stable isotope ratios appears therefore as a new and remarkable analytical tool for the discrimination or the identification of a substance with a definite source. However, much research is still needed to assess the validity of the results in order to use them either in an operational prospect or in court. Through the isotopic study of black powders and ammonium nitrates, this research aims at evaluating the contribution of isotope ratio mass spectrometry to the investigation of explosives, both from a pre-blast and from a post-blast approach. More specifically, the goal of the research is to provide additional elements necessary to a valid interpretation of the results, when used in explosives investigation. This work includes a fundamental study on the variability of the isotopic profile of black powder and ammonium nitrate in both space and time. On one hand, the inter-variability between manufacturers and, particularly, the intra-variability within a manufacturer has been studied. On the other hand, the stability of the isotopic profile over time has been evaluated through the aging of these substances exposed to different environmental conditions. The second part of this project considers the applicability of this high-precision technology to traces and residues of explosives, taking account of the characteristics specific to the field, including their sampling, a probable isotopic fractionation during the explosion, and the interferences with the matrix of the site.

17/2/20, procès [de Joseph] Caillaux [Sénat, Haute Cour de Justice] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 58080

17/2/20, procès [de Joseph] Caillaux [Sénat, Haute Cour de Justice] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 58085

17/4/20, procès Caillaux [Sénat, Haute Cour de Justice] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 58940

17/4/20, procès Caillaux [Sénat, Haute Cour de Justice] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 58943

19/4/20, procès Caillaux, plaidoirie de Maître Moro-Giafferi [Sénat, Haute Cour de Justice] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 58952

21/4/20, procès Caillaux [Sénat, Haute Cour de Justice] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 58994

21/4/20, procès Caillaux [Sénat, Haute Cour de Justice] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 58995

21/4/20, procès Caillaux [Sénat, Haute Cour de Justice] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 58998

21/4/20, procès Caillaux [Sénat, Haute Cour de Justice] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 59002

pH Sensitive surfactants from lysine: assessment of their cytotoxicity and environmental behavior

The toxicity and environmental behavior of new pH-sensitive surfactants from lysine are presented. Three different chemical structures are studied: surfactants with one amino acid and one alkyl chain, surfactants with two amino acids on the polar head and one alkyl chain, and gemini surfactants. The pH sensitivity of these compounds can be tuned by modifying their chemical structures. Cytotoxicity has been evaluated using erythrocytes and fibroblast cells. The toxic effects against these cells depend on the hydrophobicity of the molecules as well as their cationic charge density. The effect of hydrophobicity and cationic charge density on toxicity is different for each type of cells. For erythrocytes, the toxicity increases as hydrophobicity and charge density increases. Nevertheless, for fibroblasts cationic charge density affects cytotoxicity in the opposite way: the higher charge density, the lower the toxicity. The effect of the pH on hemolysis has been evaluated in detail. The aquatic toxicity was established using Daphnia magna. All surfactants yielded EC50 values considerably higher than that reported for cationic surfactants based on quaternary ammonium groups. Finally, their biodegradability was evaluated using the CO2 headspace test (ISO 14593). These lysine derivatives showed high levels of biodegradation under aerobic conditions and can be classified as"readily biodegradable compounds".

Potential impact of environmental bacteriophages in spreading antibiotic resistance genes

The idea that bacteriophage transduction plays a role in the horizontal transfer of antibiotic resistance genes is gaining momentum. Such transduction might be vital in horizontal transfer from environmental to human bodyassociated biomes and here we review many lines of evidence supporting this notion. It is well accepted that bacteriophages are the most abundant entities in most environments, where they have been shown to be quite persistent. This fact, together with the ability of many phages to infect bacteria belonging to different taxa, makes them suitable vehicles for gene transfer. Metagenomic studies confirm that substantial percentages of the bacteriophage particles present in most environments contain bacterial genes, including mobile genetic elements and antibiotic resistance genes. When specific genes of resistance to antibiotics are detected by real-time PCR in the bacteriophage populations of different environments, only tenfold lower numbers of these genes are observed, compared with those found in the corresponding bacterial populations. In addition, the antibiotic resistance genes from these bacteriophages are functional and generate resistance to the bacteria when these genes are transfected. Finally, reports about the transduction of antibiotic resistance genes are on the increase.