Dominant Role of CD80–CD86 Over CD40 and ICOSL in the Massive Polyclonal B Cell Activation Mediated by LATY136F CD4+ T Cells

Coordinated interactions between T and B cells are crucial for inducing physiological B cell responses. Mutant mice in which tyrosine 136 of linker for activation of T cell (LAT) is replaced by a phenylalanine (LatY136F) exhibit a strong CD4+ T cell proliferation in the absence of intended immunization. The resulting effector T cells produce high amounts of TH2 cytokines and are extremely efficient at inducing polyclonal B cell activation. As a consequence, these LatY136F mutant mice showed massive germinal center formations and hypergammaglobulinemia. Here, we analyzed the involvement of different costimulators and their ligands in such T–B interactions both in vitro and in vivo, using blocking antibodies, knockout mice, and adoptive transfer experiments. Surprisingly, we showed in vitro that although B cell activation required contact with T cells, CD40, and inducible T cell costimulator molecule-ligand (ICOSL) signaling were not necessary for this process. These observations were further confirmed in vivo, where none of these molecules were required for the unfolding of the LAT CD4+ T cell expansion and the subsequent polyclonal B cell activation, although, the absence of CD40 led to a reduction of the follicular B cell response. These results indicate that the crucial functions played by CD40 and ICOSL in germinal center formation and isotype switching in physiological humoral responses are partly overcome in LatY136F mice. By comparison, the absence of CD80–CD86 was found to almost completely block the in vitro B cell activation mediated by LatY136F CD4+ T cells. The role of CD80–CD86 in T–B cooperation in vivo remained elusive due to the upstream implication of these costimulatory molecules in the expansion of LatY136F CD4+ T cells. Together, our data suggest that CD80 and CD86 costimulators play a key role in the polyclonal B cell activation mediated by LatY136F CD4+ T cells even though additional costimulatory molecules or cytokines are likely to be required in this process

Approche physiopathologique et chronobiologique de la trypanosomose Africaine expérimentale

La trypanosomose humaine Africaine ou maladie du sommeil provoquée par Trypanosoma brucei (T. b.) gambiense ou rhodesiense évolue généralement en deux stades, parfois difficiles à distinguer. Les symptômes du premier stade lymphatico-sanguin sont aspécifiques alors que le stade méningo-encéphalitique se manifeste par des signes neurologiques et l'apparition des troubles du cycle veille-sommeil. Dans un modèle expérimental de rat infecté par T. b. brucei, nous avons décrit une évolution similaire en deux stades : un premier stade ne présentant pas de symptômes évidents suivi d'un second stade où une altération majeure des rythmes circadiens est observée. Le deuxième stade débute à l'apparition d'un syndrome clinique, associant anorexie, cachexie, hypothermie et hypo-activité. Ce syndrome peut apporter une aide intéressante dans la compréhension des mécanismes physiopathologiques et la mise au point de protocoles de recherche de traitementsLYON1-BU.Sciences (692662101) / SudocSudocFranceF

Bcl-2/Bax protein expression in heart, slow-twitch and fast-twitch muscles in young rats growing under chronic hypoxia conditions.

International audienceWe have studied the magnitude of apoptosis in heart, slow-twitch skeletal muscle (soleus) and fast-twitch skeletal muscle (gastrocnemius) of rats exposed to 3 weeks in vivo chronic hypoxia. Apoptosis was evaluated biochemically by DNA laddering and by TUNEL and annexin V-staining. The expression of Bax and Bcl-2 proteins was determined by immunohistochemistry and Western blotting. Western blot analysis revealed only a slight difference in Bax expression among the different tissues under normoxic and hypoxic conditions; therefore we can consider that Bax protein is constitutively expressed in muscle tissues. However a singular pattern of Bcl-2 expression was observed among the different tissues under normoxic conditions. Bcl-2 protein was more expressed in fast-twitch glycolytic muscles than in slow-twitch or oxidative muscles with a highest value found in gastrocnemius (4926 +/- 280 AU), followed by soleus (2138 +/- 200 AU) and a very low expression was displayed in the heart muscle (543 +/- 50 AU). After exposure to hypoxia for 21 days (10% O2), Bcl-2 protein expression markedly increased, (44%) in gastrocnemius, (323%) in soleus and (1178%) in heart, with significant differences (p < 0.05 student t-test), reaching a similar threshold of expression in both types of muscles. Furthermore, no sign of apoptosis was detected by TUNEL assay, annexin V-binding assay or DNA electrophoresis analysis. The latter suggested some indiscriminate fragmentations of DNA without apoptosis. In conclusion, we postulate that these protein modifications could represent a adaptative mechanism allowing a better protection against the lack of oxygen in oxidative muscles by preventing apoptosis

The enhancement of radiotherapy efficacy with docetaxel-titanate nanotubes as a new nanohybrid for localized high risk prostate cancer

International audienceFrom 30% to 50% of high risk prostate cancer patients who undergo radiation therapy (RT) will have a biochemical failure. These failures are either due to a poor local control or to distant disease which may also be related to a local failure. Taxane-based chemotherapy has proved to be useful in prostate cancer. Combining chemotherapy, such as docetaxel (DXL), with RT can enhance its efficiency, however systemic injection of the classical formulation leads to 95% uptake by healthy tissues whereas 2−5% only reach tumors; adverse side effects are a crucial problem. Moreover, multidrug resistance mechanisms often limit drug efficacy by decreasing tumor cell intracellular concentration of drugs. There is interest to develop nanocarrier of DXL to maintain drug inside cancer cells by improving its efficacy. In a previous in vitro study, we have highlighted that titanate nanotubes (TiONTs) which have a needle shape can enter and stay inside cancer cells until 10 days without cytotoxic effects induction. We suggest in this study to develop TiONt-DXL nanocarrier and to evaluate its in vivo biodistribution as well as its efficacy in association with RT on a prostate cancer model

Docetaxel-titanate nanotubes enhance radiosensitivity in an androgen-independent prostate cancer model

IF 4.320International audienceAround 40% of high-risk prostate cancer patients who undergo radiotherapy (RT) will experience biochemical failure. Chemotherapy, such as docetaxel (DTX), can enhance the efficacy of RT. Multidrug resistance mechanisms often limit drug efficacy by decreasing intracellular concentrations of drugs in tumor cells. It is, therefore, of interest to develop nanocarriers of DTX to maintain the drug inside cancer cells and thus improve treatment efficacy. The purpose of this study was to investigate the use of titanate nanotubes (TiONts) to develop a TiONts-DTX nanocarrier and to evaluate its radiosensitizing in vivo efficacy in a prostate cancer model. In vitro cytotoxic activity of TiONts-DTX was evaluated using an MTS assay. The biodistribution of TiONts-DTX was analyzed in vivo by single-photon emission computed tomography. The benefit of TiONts-DTX associated with RT was evaluated in vivo. Eight groups with seven mice in each were used to evaluate the efficacy of the nanohybrid combined with RT: control with buffer IT injection ± RT, free DXL ± RT, TiONts ± RT and TiONts-DXL ± RT. Mouse behavior, health status and tumor volume were monitored twice a week until the tumor volume reached a maximum of 2,000 mm3. More than 70% of nanohybrids were localized inside the tumor 96 h after administration. Tumor growth was significantly slowed by TiONts-DTX associated with RT, compared with free DTX in the same conditions (P=0.013). These results suggest that TiONts-DTX improved RT efficacy and might enhance local control in high-risk localized prostate cancer

CD93 is required for maintenance of antibody secretion and persistence of plasma cells in the bone marrow niche

Plasma cells represent the end stage of B-cell development and play a key role in providing an efficient antibody response, but they are also involved in numerous pathologies. Here we show that CD93, a receptor expressed during early B-cell development, is reinduced during plasma-cell differentiation. High CD93/CD138 expression was restricted to antibody-secreting cells both in T-dependent and T-independent responses as naive, memory, and germinal-center B cells remained CD93-negative. CD93 was expressed on (pre)plasmablasts/plasma cells, including long-lived plasma cells that showed decreased cell cycle activity, high levels of isotype-switched Ig secretion, and modification of the transcriptional network. T-independent and T-dependent stimuli led to re-expression of CD93 via 2 pathways, either before or after CD138 or Blimp-1 expression. Strikingly, while humoral immune responses initially proceeded normally, CD93-deficient mice were unable to maintain antibody secretion and bone-marrow plasma-cell numbers, demonstrating that CD93 is important for the maintenance of plasma cells in bone marrow niches