Masses of the components of SB2 binaries observed with Gaia. I. Selection of the sample and mass ratios of 20 new SB2s discovered with Sophie

In anticipation of the Gaia astrometric mission, a large sample of spectroscopic binaries is being observed since 2010 with the Sophie spectrograph at the Haute--Provence Observatory. Our aim is to derive the orbital elements of double-lined spectroscopic binaries (SB2s) with an accuracy sufficient to finally obtain the masses of the components with relative errors as small as 1% when the astrometric measurements of Gaia are taken into account. Simultaneously, the luminosities of the components in the Gaia photometric band G will also be obtained. Our observation program started with 200 SBs, including 152 systems that were only known as single-lined. Thanks to the high efficiency of the Sophie spectrograph, an additional component was found for 25 SBs. After rejection of 5 multiple systems, 20 new SB2s were retained, including 8 binaries with evolved primary, and their mass ratios were derived. Our final sample contains 68 SB2s, including 2 late-type giants and 10 other evolved stars.Comment: 8 pages, 3 figures, accepted for publication in MNRA

CD4+CD25+ Immunoregulatory T Cells: New Therapeutics for Graft-Versus-Host Disease

CD4+CD25+ immunoregulatory T cells play a pivotal role in preventing organ-specific autoimmune diseases and in tolerance induction to allogeneic organ transplants. We investigated whether these cells could also control graft-versus-host disease (GVHD), the main complication after allogeneic hematopoietic stem cell transplantation (HSCT). Here, we show that the few CD4+CD25+ T cells naturally present in the transplant regulate GVHD because their removal from the graft dramatically accelerates this disease. Furthermore, the addition of freshly isolated CD4+CD25+ T cells at time of grafting significantly delays or even prevents GVHD. Ex vivo–expanded CD4+CD25+ regulatory T cells obtained after stimulation by allogeneic recipient-type antigen-presenting cells can also modulate GVHD. Thus, CD4+CD25+ regulatory T cells represent a new therapeutic tool for controlling GVHD in allogeneic HSCT. More generally, these results outline the tremendous potential of regulatory T cells as therapeutics

Continuous Activation of Autoreactive CD4+ CD25+ Regulatory T Cells in the Steady State

Despite a growing interest in CD4+ CD25+ regulatory T cells (Treg) that play a major role in self-tolerance and immunoregulation, fundamental parameters of the biology and homeostasis of these cells are poorly known. Here, we show that this population is composed of two Treg subsets that have distinct phenotypes and homeostasis in normal unmanipulated mice. In the steady state, some Treg remain quiescent and have a long lifespan, in the order of months, whereas the other Treg are dividing extensively and express multiple activation markers. After adoptive transfer, tissue-specific Treg rapidly divide and expand preferentially in lymph nodes draining their target self-antigens. These results reveal the existence of a cycling Treg subset composed of autoreactive Treg that are continuously activated by tissue self-antigens

Stealth nanocarriers based sterosomes using PEG post-insertion process

Sterosomes (STEs), a new and promising non-phospholipidic liposome platform based on palmitic acid (PA) and cholesterol (Chol) mixtures, need to have polyethylene glycol (PEG) chains grafted to their surface in order to obtain long-circulating nanocarriers in the blood stream. A post-insertion method was chosen to achieve this modification. The post-insertion process of PEG-modified distearoylphosphoethanolamine (DSPE-PEG) was monitored using the zeta potential value of STEs. Various conditions including PEG chain length and the DSPE-PEG/PA-Chol ratio, were explored. Zeta potential of STEs changed from about -40mV for non-modified STEs to values close to 0 mV by the end of the process, i.e. for PEG-modified STEs. The kinetics of DSPE-PEG insertion and the stability of the resulting PEG-modified STEs were not considerably influenced, within the investigated range, by changes in PEG chain lengths and in DSPE-PEG/PA-Chol proportion. The post-insertion of PEG chains reduced in vitro complement activation as well as in vitro macrophage uptake compared to the non-modified STEs. Moreover, longer blood circulation time in mice was established for PEG-modified STEs intravenously injected compared to non-modified STEs. These results establish that post-insertion process of PEG chains to STEs is a promising strategy for developing long-term circulating drug delivery nanocarriers

Lymphocytes T régulateurs CD4+CD25+ : concepts actuels et potentiels thérapeutiques

La population de lymphocytes T CD4+, caractérisée par une expression constitutive du CD25, joue un rôle essentiel dans la régulation de nombreuses maladies auto-immunes. Ces lymphocytes T CD4+CD25+ semblent agir par inhibition de l’activation des lymphocytes T CD4+ et CD8+. Ce sont des cellules auto-réactives d’origine thymique. Elles présentent un potentiel thérapeutique, non seulement dans le contrôle des maladies auto-immunes, mais également dans celui du rejet de greffe d’organe ou de la maladie du greffon contre l’hôte

Stimulation des lymphocytes T régulateurs chez la souris dans un contexte inflammatoire comme le diabète auto-immun

PARIS-BIUSJ-Biologie recherche (751052107) / SudocSudocFranceF