The transcriptional repressor Bcl6 is a critical arbiter of T helper cell fate, promoting the follicular helper (Tfh) lineage while repressing other T helper cell lineages. Bcl6-deficient (Bcl6-/-) mice develop a spontaneous and severe Th2-type inflammatory disease, thus warranting assessment of Bcl6 in Treg cell function. Bcl6-/- Tregs were competent at suppressing T cell proliferation in vitro and Th1-type colitogenic T cell responses in vivo. In contrast, Bcl6-/- Treg cells strongly exacerbated lung inflammation in a model of allergic airway disease, and promoted higher Th2 responses, including systemic up-regulation of microRNA-21. Further, Bcl6-/- Tregs were selectively impaired at controlling Th2 responses but not Th1 and Th17 responses, in mixed chimeras of Bcl6-/- bone marrow with Foxp3-/- bone marrow. Bcl6-/- Tregs displayed increased levels of the Th2 transcription factor Gata3 and other Th2 and Treg genes. Bcl6 potently repressed Gata3 transcriptional transactivation, providing a mechanism for the increased expression of Th2 genes by Bcl6-/- Tregs. Gata3 has a critical role in regulating Foxp3 expression and functional fitness of Tregs, however, the signal that regulates Gata3 and restricts its transactivation of Th2 cytokines in Tregs has remained unexplored. Our results identify Bcl6 as an essential transcription factor regulating Gata3 activity in Tregs. Thus, Bcl6 represents a crucial regulatory layer in the Treg functional program, required for specific suppression of Gata3 and Th2 effector responses by Tregs.

The presence of infectious microorganisms in urinary stones is commonly inferred from stone composition, especially by the presence of struvite in a stone. The presence of highly carbonated apatite has also been proposed as a marker of the presence of bacteria within a stone. We retrospectively studied 368 patients who had undergone percutaneous nephrolithotomy, and who also had culture results for both stone and urine. Urine culture showed no association with stone mineral content, but stone culture was more often positive in struvite containing stones (73% positive) and majority apatite stones (65%) than in other stone types (54%, lower than the others, P<0.02). In 51 patients in which the carbonate content of apatite could be measured, carbonate in the apatite was weakly predictive of positive stone culture with an optimal cutoff value of 13.5% carbonate (sensitivity 0.61, specificity 0.80). In positive cultures of stones (all mineral types combined), organisms that characteristically produce urease were present in 71% of the cases, with no difference in this proportion among different types of stone. In summary, the type of mineral in the stone was predictive of positive stone culture, but this correlation is imperfect, as over half of non-struvite, non-apatite stones were found to harbor culturable organisms. We conclude that mineral type is an inadequate predictor of whether a stone contains infectious organisms, and that stone culture is more likely to provide information useful to the management of patients undergoing percutaneous nephrolithotomy.

Background and Purpose: Struvite in kidney stones is an important marker for infection. In kidney stone samples, struvite is known to be prone to chemical breakdown, but no data exist on the stability of samples stored in dry form. The objective of this study was to examine stability of struvite under increasingly poor conditions of storage. Materials and Methods: Samples of struvite kidney stones were broken to obtain 38 pieces averaging 67 mg in weight, and these were randomized into four storage conditions: Airtight containers stored in the dark, open containers in the dark, open containers in ambient light, and open containers at elevated temperature (40°C). Pieces were left for 6 months, and then analyzed for changes using micro CT and Fourier transform infrared spectroscopy (FT-IR). Results: Initial samples proved to be struvite, indicating no transformation in the large specimens that had been stored in airtight containers in the dark for more than 6 years before this study. Pieces of struvite taken from these large specimens appeared unchanged by micro CT and FT-IR after being stored in closed containers for 6 months, but 8 of 9 pieces in open containers showed the presence of newberyite in surface layers, as did 10 of 10 pieces in open containers out in ambient light. All pieces stored at 40°C showed transformation of struvite, with 60% of the pieces showing the presence of amorphous phosphates, indicating complete breakdown of struvite in the surface layers of the pieces. Conclusion: We conclude that struvite in dry kidney stone samples is stable when the specimens are stored in airtight containers at room temperature, even after several years.