The outer membrane of gram-negative bacteria is a permeability barrier that prevents the efficient uptake of molecules with large scaffolds. As a consequence, a number of antibiotic classes are ineffective against gram-negative strains. Herein we carried out a high throughput screen for small molecules that make the outer membrane of Escherichia coli more permeable. We identified MAC13243, an inhibitor of the periplasmic chaperone LolA that traffics lipoproteins from the inner to the outer membrane. We observed that cells were (1) more permeable to the fluorescent probe 1-N-phenylnapthylamine, and (2) more susceptible to large-scaffold antibiotics when sub-inhibitory concentrations of MAC13243 were used. To exclude the possibility that the permeability was caused by an off-target effect, we genetically reconstructed the MAC13243-phenotype by depleting LolA levels using the CRISPRi system.

Galectin-1 is a galactoside-binding lectin expressed in multiple tissues that has pleiotropic immunomodulatory functions. We previously showed that galectin-1 activates human monocyte-derived dendritic cells (MDDCs) and triggers a specific genetic program that up-regulates DC migration through the extracellular matrix, an integral property of mucosal DCs. Here, we identify the galectin-1 receptors on MDDCs and immediate downstream effectors of galectin-1-induced MDDC activation and migration. Galectin-1 binding to surface CD43 and CD45 on MDDCs induced an unusual unipolar co-clustering of these receptors and activates a dose-dependent calcium flux that is abrogated by lactose. Using a kinome screen and a systems biology approach, we identified Syk and protein kinase C tyrosine kinases as mediators of the DC activation effects of galectin-1. Galectin-1, but not lipopolysaccharide, stimulated Syk phosphorylation and recruitment of phosphorylated Syk to the CD43 and CD45 co-cluster on MDDCs. Inhibitors of Syk and protein kinase C signaling abrogated galectin-1-induced DC activation as monitored by interleukin-6 production; and MMP-1, -10, and -12 gene up-regulation; and enhanced migration through the extracellular matrix. The latter two are specific features of galectin-1-activated DCs. Interestingly, we also found that galectin-1 can prime DCs to respond more quickly to low dose lipopolysaccharide stimulation. Finally, we underscore the biological relevance of galectin-1-enhanced DC migration by showing that intradermal injection of galectin-1 in MRL-fas mice, which have a defect in skin DC emigration, increased the in vivo migration of dermal DCs to draining lymph nodes. Dendritic cells (DCs)5 are critical regulators of immunity that sample and present antigen, initiate adaptive immune responses through T cell interactions, and maintain self-tolerance through T cell instruction (1, 2). To effectively mount an immune response, DCs must encounter antigen and receive a signal to initiate an activation program termed "maturation." Both exogenous and endogenous signals can initiate DC maturation. Exogenous maturation signals include Toll-like receptor ligation via pathogen components such as bacterial proteins (e.g. LPS), bacterial DNA (through CpG-containing motifs), and viral double-stranded RNA (3, 4). In synergy with these pathogen signals, or alone, endogenous DC activators include inflammatory cytokines, prostaglandins, and other danger signals (5).Recent work has also demonstrated that galectins, a family of endogenous ␤-galactoside binding lectins, can initiate DC maturation (6 -8). The galectins have numerous known immunomodulatory activities involving T and B cells, but the role of these lectins in DC function is only beginning to be investigated. Galectin-9 matures DCs into IL-12-producing cells, which can elicit a Th1 response from T cells following co-culture (8). On the other hand, galectin-3 influences the type of adaptive immune response initiated by DCs but does not directly affect the maturation proc...

By adapting OPT to include the capability of imaging in the near infrared (NIR) spectrum, we here illustrate the possibility to image larger bodies of pancreatic tissue, such as the rat pancreas, and to increase the number of channels (cell types) that may be studied in a single specimen. We further describe the implementation of a number of computational tools that provide: 1/ accurate positioning of a specimen's (in our case the pancreas) centre of mass (COM) at the axis of rotation (AR) 2 ; 2/ improved algorithms for post-alignment tuning which prevents geometric distortions during the tomographic reconstruction 2 and 3/ a protocol for intensity equalization to increase signal to noise ratios in OPT-based BCM determinations 3. In addition, we describe a sample holder that minimizes the risk for unintentional movements of the specimen during image acquisition. Together, these protocols enable assessments of BCM distribution and other features, to be performed throughout the volume of intact pancreata or other organs (e.g. in studies of islet transplantation), with a resolution down to the level of individual islets of Langerhans.

Group A streptococci (GAS) express a superantigen, SpeB, having cysteine protease activity. SpeB exhibits several properties that might contribute to virulence, the most recently discovered being the ability to cleave immunoglobulin G (IgG) in a manner similar to that of papain. In the present study, we confirmed this latter finding and found that the irreversible inhibition of SpeB protease activity completely abolishes IgG cleavage. SpeB cleavage of IgG was not species restricted since SpeB cleaved both human, rabbit, and mouse IgG. In order to investigate the nature of the SpeB cleavage of IgG, antibodies were immobilized prior to exposure to SpeB, either by unspecific binding of the Fc to GAS surface proteins or by antigen-specific binding. Analysis of the IgG molecules by SDS-PAGE showed that SpeB could cleave antigen-bound antibodies, while the IgG bound to IgG-binding proteins was protected from cleavage. In a phagocytosis assay using whole blood, the M49 GAS strain NZ131 showed a significantly higher survival than its isogenic speB mutant. Furthermore, the addition of extracellular supernatant derived from an overnight culture of native NZ131 increased the survival of its isogenic speB derivative. This indicates that SpeB's ability to cleave off the Fc part of antigen-bound IgG contributes to GAS escape from opsonophagocytosis while not interfering with the formation of a host-like coat by unspecific IgG binding.

To investigate whether the multifocal inflammatory disease in TGFβ1-deficient mice is caused by self-antigen (self-Ag)-specific autoreactive T cells, or whether it is caused by antigen independent, spontaneous hyperactivation of T cells, we have generated Tgfb1 −/− and Tgfb1 −/− Rag1 −/− mice expressing the chicken OVA-specific TCR transgene (DO11.10). On a Rag1-sufficient background, Tgfb1 −/− DO11.10 mice develop a milder inflammation than do Tgfb1 −/− mice, and their T cells display a less activated phenotype. The lower level of activation correlates with the expression of hybrid TCR (transgenic TCRβ and endogenous TCRα), which could recognize self-Ag and undergo activation. In the complete absence of self-Ag recognition (Tgfb1 −/− DO11.10 Rag1 −/− mice) inflammation and T-cell activation are eliminated, demonstrating that self-Ag recognition is required for the hyper-responsiveness of TGFβ1-deficient T cells. Thus, TGFβ1 is required for the prevention of autoimmune disease through its ability to control the activation of autoreactive T cells to self-Ag.