Genetic variation in PTPN22 corresponds to altered function of T and B lymphocytes

A variant of the PTPN22 gene, 1858C/T, is associated with an increased risk for the development of a wide array of autoimmune disorders. It is known that the protein tyrosine phosphatase Lyp encoded by this gene has an inhibitory effect on the proximal TCR signaling pathways. However, the consequences of carrying this variant and the mechanism by which it contributes to the development of autoimmunity are poorly understood. In this study, we demonstrate that homozygosity for this variant results in a profound deficit in T cell responsiveness to Ag stimulation. Heterozygosity for the variant allele is associated with reduced responsiveness of CD4+ memory T cells, characterized by diminished calcium mobilization, expression of CD25, and IL-10 production upon TCR stimulation. Additionally, the presence of the variant allele is associated with an increase in circulating memory T cells. We further demonstrate that these effects are not limited to the T cell compartment. Individuals with the variant allele have fewer memory B cells and these cells display a reduced response to stimulation via the BCR indicative of a B cell intrinsic defect. By identifying an immunologic phenotype in healthy subjects which correlates with the PTPN22 1858C/T genotype, we can now explore specific hypotheses regarding pathogenesis of diseases associated with the PTPN22 1858T variant.     

GarA is an essential regulator of metabolism in Mycobacterium tuberculosis

Alpha‐ketoglutarate is a key metabolic intermediate at the crossroads of carbon and nitrogen metabolism, whose fate is tightly regulated. In mycobacteria the protein GarA regulates the tricarboxylic acid cycle and glutamate synthesis by direct binding and regulation of three enzymes that use α‐ketoglutarate. GarA, in turn, is thought to be regulated via phosphorylation by protein kinase G and other kinases. We have investigated the requirement for GarA for metabolic regulation during growth in vitro and in macrophages. GarA was found to be essential to Mycobacterium tuberculosis, but dispensable in non‐pathogenic Mycobacterium smegmatis. Disruption of garA caused a distinctive, nutrient‐dependent phenotype, fitting with its proposed role in regulating glutamate metabolism. The data underline the importance of the TCA cycle and the balance with glutamate synthesis in M. tuberculosis and reveal vulnerability to disruption of these pathways.     

In Vivo Labeling by CD73 Marks Multipotent Stromal Cells and Highlights Endothelial Heterogeneity in the Bone Marrow Niche

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Utilization of Methylthio-s-Triazine for Growth of Soil Fungi

Aspergillus niger van Tieghem, Aspergillus tamarii Kita, and Aspergillus flavus Link ex Fries utilized the methylthio moiety of 2,4-bis(isopropylamino) -6-methyl-mercapto-s-triazine (prometryne) as a sulfur nutrient source. Other soil fungal isolates not affected by prometryne concentrations to 1 mg/ml culture included: Aspergillus oryzae (Ahlburg) Cohn, Curvularia lunata (Wakker) Boedijn, Trichoderma viride Persoon ex Fries, Alternaria tenuis Nees ex Corda, Penicillium funiculosum Thom, and Paecilomyces varioti Bainier.     

Low-dose antigen promotes induction of FOXP3 in human CD4+ T cells

Low Ag dose promotes induction and persistence of regulatory T cells (Tregs) in mice, yet few studies have addressed the role of Ag dose in the induction of adaptive CD4(+)FOXP3(+) Tregs in humans. To this end, we examined the level of FOXP3 expression in human CD4(+)CD25(-) T cells upon activation with autologous APCs and varying doses of peptide. Ag-specific T cells expressing FOXP3 were identified by flow cytometry using MHC class II tetramer (Tmr). We found an inverse relationship between Ag dose and the frequency of FOXP3(+) cells for both foreign Ag-specific and self Ag-specific T cells. Through studies of FOXP3 locus demethylation and helios expression, we determined that variation in the frequency of Tmr(+)FOXP3(+) T cells was not due to expansion of natural Tregs, but instead, we found that induction, proliferation, and persistence of FOXP3(+) cells was similar in high- and low-dose cultures, whereas proliferation of FOXP3(-) T cells was favored in high Ag dose cultures. The frequency of FOXP3(+) cells positively correlated with suppressive function, indicative of adaptive Treg generation. The frequency of FOXP3(+) cells was maintained with IL-2, but not upon restimulation with Ag. Together, these data suggest that low Ag dose favors the transient generation of human Ag-specific adaptive Tregs over the proliferation of Ag-specific FOXP3(-) effector T cells. These adaptive Tregs could function to reduce ongoing inflammatory responses and promote low-dose tolerance in humans, especially when Ag exposure and tolerance is transient.     

Unexpected durability of PKH 26 staining on rat adipocytes

In a case of autologous mature fat cell transplantation to an individual rat, persistence of adipose staining with PKH26 was detected 14.5 months later. Fluorescent fat cells with spotty surface markings were easily visible. Such a long period of persistence and stability of staining exceeds the expectation from previous reports, and the given half-life of the substance. This finding encourages the use of the dye for long-term follow-up of connective tissue cells, especially adipocytes and preadipocytes, following transplantation.     

Influence of Temperature on Steady-State Growth of Colonies of Pseudomonas fluorescens

Diameters of surface colonies of Pseudomonas fluorescens were observed to increase linearly with time at temperatures from 30 to 0 C.