Requirement for MyD88 signaling in B cells and dendritic cells for germinal center anti-nuclear antibody production in Lyn-deficient mice.

The intracellular tyrosine kinase Lyn mediates inhibitory receptor function in B cells and myeloid cells, and Lyn(-/-) mice spontaneously develop an autoimmune and inflammatory disease that closely resembles human systemic lupus erythematosus. TLR-signaling pathways have been implicated in the production of anti-nuclear Abs in systemic lupus erythematosus and mouse models of it. We used a conditional allele of Myd88 to determine whether the autoimmunity of Lyn(-/-) mice is dependent on TLR/MyD88 signaling in B cells and/or in dendritic cells (DCs). The production of IgG anti-nuclear Abs, as well as the deposition of these Abs in the glomeruli of the kidneys, leading to glomerulonephritis in Lyn(-/-) mice, were completely abolished by selective deletion of Myd88 in B cells, and autoantibody production and glomerulonephritis were delayed or decreased by deletion of Myd88 in DCs. The reduced autoantibody production in mice lacking MyD88 in B cells or DCs was accompanied by a dramatic decrease in the spontaneous germinal center (GC) response, suggesting that autoantibodies in Lyn(-/-) mice may depend on GC responses. Consistent with this view, IgG anti-nuclear Abs were absent if T cells were deleted (TCRß(-/-) TCRδ(-/-) mice) or if T cells were unable to contribute to GC responses as the result of mutation of the adaptor molecule SAP. Thus, the autoimmunity of Lyn(-/-) mice was dependent on T cells and on TLR/MyD88 signaling in B cells and in DCs, supporting a model in which DC hyperactivity combines with defects in tolerance in B cells to lead to a T cell-dependent systemic autoimmunity in Lyn(-/-) mice.

Ndfip1 enforces a requirement for CD28 costimulation by limiting IL-2 production.

Although the pathways that permit IL-2 production and the full activation of T cells upon Ag encounter are fairly well defined, the negative regulatory circuits that limit these pathways are poorly understood. In this study, we show that the E3 ubiquitin ligase adaptor Ndfip1 directs one such negative regulatory circuit. T cells lacking Ndfip1 produce IL-2, upregulate IL-2Rα, and proliferate, in the absence of CD28 costimulation. Furthermore, T cells in mice lacking both Ndfip1 and CD28 become activated, produce IL-4, and drive inflammation at barrier surfaces. Ndfip1 constrains T cell activation by limiting the duration of IL-2 mRNA expression after TCR stimulation. Ndfip1 and IL-2 have a similar expression pattern, and, following TCR stimulation, expression of both Ndfip1 and IL-2 requires the activity of NFAT and Erk. Taken together, these data support a negative regulatory circuit in which factors that induce IL-2 expression downstream of TCR engagement also induce the expression of Ndfip1 to limit the extent of IL-2 production and, thus, dampen T cell activation.

Sphaerochaeta globosa gen. nov., sp. nov. and Sphaerochaeta pleomorpha sp. nov., free-living, spherical spirochaetes.

Free-living bacteria with spherical cells 0.5-2.5 µm in diameter were isolated from freshwater sediment. 16S rRNA gene sequence analysis placed the new isolates within the phylum Spirochaetes ('spirochaetes'). The isolates never displayed a helical morphology or motility. Growth occurred in the presence of 100 mg ampicillin l(-1) in complex and defined mineral salts medium amended with vitamins, yeast extract and monosaccharides, disaccharides or soluble starch as fermentable substrates. Two distinct isolates, designated Buddy(T) and Grapes(T), exhibited doubling times of 21±2 and 15±1 h in glucose-amended medium and grew at 15-37 and 15-30 °C. Optimum growth was observed between 25 and 30 °C and pH 6.5-7.5, with no growth below pH 5 or above pH 10. Hexose and pentose fermentation yielded ethanol, acetate and formate as major end products. Growth was strictly fermentative and anaerobic, but the isolates tolerated brief oxygen exposure. Nitrate, sulfate, thiosulfate and carbon dioxide were not used as electron acceptors, but soluble Fe(III) was reduced to Fe(II) in glucose-amended medium. The DNA G+C base contents of isolates Buddy(T) and Grapes(T) were 45.5-46.4 and 47.0-49.2 mol%, respectively. Phospholipid fatty acid (PLFA) profiles contained large proportions of C(14:0) and C(16:0) straight-chain saturated fatty acids; C(16:1)ω7c and C(16:1)ω9c dominated the mono-unsaturated PLFAs in isolate Grapes(T), whereas isolate Buddy(T) also possessed C(18:1)ω5c, C(18:1)ω7c and C(18:1)ω9c fatty acids. Branched monoenoic acids accounted for up to 12.4 and 30% of the total PLFA in isolates Grapes(T) and Buddy(T), respectively. Based on their unique morphological features and the phylogenetic distance from their closest relatives, we propose the new genus, Sphaerochaeta gen. nov., to accommodate the new isolates within the novel species Sphaerochaeta globosa sp. nov. (type strain Buddy(T) =DSM 22777(T) =ATCC BAA-1886(T)) and Sphaerochaeta pleomorpha sp. nov. (type strain Grapes(T) =DSM 22778(T) =ATCC BAA-1885(T)). Sphaerochaeta globosa is the type species of the genus.

TGF-ß induces the expression of the adaptor Ndfip1 to silence IL-4 production during iTreg cell differentiation.

Mice deficient in the adaptor Ndfip1 develop inflammation at sites of environmental antigen exposure. We show here that such mice had fewer inducible regulatory T cells (iT(reg) cells). In vitro, Ndfip1-deficient T cells expressed normal amounts of the transcription factor Foxp3 during the first 48 h of iT(reg) cell differentiation; however, this expression was not sustained. Abortive Foxp3 expression was caused by production of interleukin 4 (IL-4) by Ndfip1(-/-) cells. We found that Ndfip1 expression was transiently upregulated during iT(reg) cell differentiation in a manner dependent on transforming growth factor-ß (TGF-ß). Once expressed, Ndfip1 promoted degradation of the transcription factor JunB mediated by the E3 ubiquitin ligase Itch, thus preventing IL-4 production. On the basis of our data, we propose that TGF-ß signaling induces Ndfip1 expression to silence IL-4 production, thus permitting iT(reg) cell differentiation.

Geobacter lovleyi sp. nov. strain SZ, a novel metal-reducing and tetrachloroethene-dechlorinating bacterium.

A bacterial isolate, designated strain SZ, was obtained from noncontaminated creek sediment microcosms based on its ability to derive energy from acetate oxidation coupled to tetrachloroethene (PCE)-to-cis-1,2-dichloroethene (cis-DCE) dechlorination (i.e., chlororespiration). Hydrogen and pyruvate served as alternate electron donors for strain SZ, and the range of electron acceptors included (reduced products are given in brackets) PCE and trichloroethene [cis-DCE], nitrate [ammonium], fumarate [succinate], Fe(III) [Fe(II)], malate [succinate], Mn(IV) [Mn(II)], U(VI) [U(IV)], and elemental sulfur [sulfide]. PCE and soluble Fe(III) (as ferric citrate) were reduced at rates of 56.5 and 164 nmol min(-1) mg of protein(-1), respectively, with acetate as the electron donor. Alternate electron acceptors, such as U(VI) and nitrate, did not inhibit PCE dechlorination and were consumed concomitantly. With PCE, Fe(III) (as ferric citrate), and nitrate as electron acceptors, H(2) was consumed to threshold concentrations of 0.08 +/- 0.03 nM, 0.16 +/- 0.07 nM, and 0.5 +/- 0.06 nM, respectively, and acetate was consumed to 3.0 +/- 2.1 nM, 1.2 +/- 0.5 nM, and 3.6 +/- 0.25 nM, respectively. Apparently, electron acceptor-specific acetate consumption threshold concentrations exist, suggesting that similar to the hydrogen threshold model, the measurement of acetate threshold concentrations offers an additional diagnostic tool to delineate terminal electron-accepting processes in anaerobic subsurface environments. Genetic and phenotypic analyses classify strain SZ as the type strain of the new species, Geobacter lovleyi sp. nov., with Geobacter (formerly Trichlorobacter) thiogenes as the closest relative. Furthermore, the analysis of 16S rRNA gene sequences recovered from PCE-dechlorinating consortia and chloroethene-contaminated subsurface environments suggests that Geobacter lovleyi belongs to a distinct, dechlorinating clade within the metal-reducing Geobacter group. Substrate versatility, consumption of electron donors to low threshold concentrations, and simultaneous reduction of electron acceptors suggest that strain SZ-type organisms have desirable characteristics for bioremediation applications.