IL-10 is a potent immunomodulatory cytokine that affects innate and acquired immune responses. The immunological consequences of IL-10 production during pulmonary tuberculosis (TB) are currently unknown, although IL-10 has been implicated in reactivation TB in humans and with TB disease in mice. Using Mycobacterium tuberculosis-susceptible CBA/J mice, we show that blocking the action of IL-10 in vivo during chronic infection stabilized the pulmonary bacterial load and improved survival. Furthermore, this beneficial outcome was highly associated with the recruitment of T cells to the lungs and enhanced T cell IFN-γ production. Our results indicate that IL-10 promotes TB disease progression. These findings have important diagnostic and/or therapeutic implications for the prevention of reactivation TB in humans.

Complexins play activating and inhibitory functions in neurotransmitter release. The complexin accessory helix inhibits release and was proposed to insert into SNARE complexes to prevent their full assembly. This model was supported by ‘superclamp’ and ‘poor-clamp’ mutations that enhanced or decreased the complexin-I inhibitory activity in cell–cell fusion assays, and by the crystal structure of a superclamp mutant bound to a synaptobrevin-truncated SNARE complex. NMR studies now show that the complexin-I accessory helix does not insert into synaptobrevin-truncated SNARE complexes in solution, and electrophysiological data reveal that superclamp mutants have slightly stimulatory or no effects on neurotransmitter release, whereas a poor-clamp mutant inhibits release. Importantly, increasing or decreasing the negative charge of the complexin-I accessory helix inhibits or stimulates release, respectively. These results suggest a new model whereby the complexin accessory helix inhibits release through electrostatic (and perhaps steric) repulsion enabled by its location between the vesicle and plasma membranes.DOI: http://dx.doi.org/10.7554/eLife.02391.001

Obesity is associated with chronic low-grade inflammation in peripheral tissues caused, in part, by the recruitment of inflammatory monocytes into adipose tissue. Studies in rodent models have also shown increased inflammation in the central nervous system (CNS) during obesity. The goal of this study was to determine whether obesity is associated with recruitment of peripheral immune cells into the CNS. To do this we used a bone marrow chimerism model to track the entry of green-fluorescent protein (GFP) labeled peripheral immune cells into the CNS. Flow cytometry was used to quantify the number of GFP+ immune cells recruited into the CNS of mice fed a high-fat diet compared to standard chow fed controls. High-fat feeding resulted in obesity associated with a 30% increase in the number of GFP+ cells in the CNS compared to control mice. Greater than 80% of the GFP+ cells recruited to the CNS were also CD45+ CD11b+ indicating that the GFP+ cells displayed characteristics of microglia/macrophages. Immunohistochemistry further confirmed the increase in GFP+ cells in the CNS of the high-fat fed group and also indicated that 93% of the recruited cells were found in the parenchyma and had a stellate morphology. These findings indicate that peripheral immune cells can be recruited to the CNS in obesity and may contribute to the inflammatory response.

Proteus mirabilis is a dimorphic bacterium which exists in liquid cultures as a 1.5-to 2.0-,um motile swimmer cell possessing 6 to 10 peritrichous flagella. When swimmer cells are placed on a surface, they differentiate by a combination of events that ultimately produce a swarmer cell. Unlike the swimmer cell, the polyploid swarmer cell is 60 to 80 ,um long and possesses hundreds to thousands of surface-induced flagella. These features, combined with multicellular behavior, allow the swarmer cells to move over a surface in a process called swarming. Transposon TnS was used to produce P. mirabUis mutants defective in wild-type swarming motility. Two general classes of mutants were found to be defective in swarming. The first class was composed of null mutants that were completely devoid of swarming motility. The majority of nonswarming mutations were the result of defects in the synthesis of flagella or in the ability to rotate the flagella. The remaining nonswarming mutants produced flagella but were defective in surface-induced elongation. Strains in the second general class of mutants, which made up more than 65% of all defects in swarming were motile but were defective in the control and coordination of multicellular swarming. Analysis of consolidation zones produced by such crippled mutants suggested that this pleiotropic phenotype was caused by a defect in the regulation of multicellular behavior. A possible mechanism controlling the cyclic process of differentiation and dedifferentiation involved in the swarming behavior of P. mirabilis is discussed.Proteus mirabilis is a motile gram-negative bacterium, similar in many aspects of its physiology to other members of the family Enterobacteriaceae, such as Escherichia coli and Salmonella typhimurium. It was originally described and named by Hauser in 1885 for the character in Homer's Odyssey who "has the power of assuming different shapes in order to escape being questioned" (quoted from reference 18). P. mirabilis is considered to be an opportunistic pathogen and is one of the principal causes of urinary infections in hospital patients with urinary catheters (32,34). Its ability to colonize the surfaces of catheters and the urinary tract may be aided by the characteristic first described more than a century ago and currently referred to as swarmer cell differentiation.When grown in suitable liquid media, P. mirabilis exists as 1.5-to 2.0-,um motile cells with 6 to 10 peritrichous flagella. These bacteria, called swimmer cells, display characteristic swimming and chemotactic behavior, moving toward nutrients and away from repellents (36). However, a dramatic change in cell morphology takes place when cells grown in liquid are transferred to a nutrient medium solidified with agar.

A technique of transposon mutagenesis involving the use of TnS on a suicide plasmid was developed for Proteus mirabilis. Analysis of the resulting exconjugants indicated that TnS transposed in P. mirabilis at a frequency of ca. 4.5 x 10-6 per recipient cell. The resulting mutants were stable and retained the transposon-encoded antibiotic resistance when incubated for several generations under nonselective conditions. The frequency of auxotrophic mutants in the population, as well as DNA-DNA hybridization to transposon sequences, confirmed that the insertion of the transposon was random and the Proteus chromosome did not contain significant insertional hot spots of transposition. Approximately 35% of the mutants analyzed possessed plasmid-acquired ampicillin resistance, although no extrachromosomal plasmid DNA was found. In these mutants, insertion of the Tn5 element and a part or all of the plasmid had occurred. Application of this technique to the study of swarmer cell differentiation in P. mirabilis is discussed.