Resident regulatory T cells reflect the immune history of individual lymph nodes.

Regulatory T cells (Tregs) are present in lymphoid and nonlymphoid tissues where they restrict immune activation, prevent autoimmunity, and regulate inflammation. Tregs in nonlymphoid tissues are typically resident, whereas those in lymph nodes (LNs) are considered to recirculate. However, Tregs in LNs are not a homogenous population, and circulation kinetics of different Treg subsets are poorly characterized. Furthermore, whether Tregs can acquire memory T cell properties and persist for extended periods after their activation in LNs is unclear. Here, we used in situ labeling with a stabilized photoconvertible protein to uncover turnover rates of Tregs in LNs in vivo. We found that, whereas most Tregs in LNs recirculate, 10 to 20% are memory-like resident cells that remain in their respective LNs for weeks to months. Single-cell RNA sequencing revealed that LN-resident cells are a functionally and ontogenetically heterogeneous population and share the same core residency gene signature with conventional CD4+ and CD8+ T cells. Resident cells in LNs did not actively proliferate and did not require continuous T cell receptor (TCR) signaling for their residency. However, resident and circulating Tregs had distinct TCR repertoires, and each LN contained exclusive clonal subpopulations of resident Tregs. Our results demonstrate that, similar to conventional T cells, Tregs can form resident memory-like populations in LNs after adaptive immune responses. Specific and local suppression of immune responses by resident Tregs in draining LNs might provide previously unidentified therapeutic opportunities for the treatment of local chronic inflammatory conditions.

Lymph node γδ and αß CD8+ T cells share migratory properties.

During immune responses, T cells differentiate into subsets with different functions and migratory properties. Here we characterize migratory behavior of endogenous αß CD8+ and γδ T cells in lymph nodes by long-term tracking following in vivo photoconversion. We identified subsets of γδ T cells with distinct circulation kinetics that closely mirrored migratory subsets of αß CD8+ T cells. Notably, αß CD8+ and γδ T cells both comprised resident populations which stayed in lymph nodes for 4 weeks without circulation or proliferation. Furthermore, in contrast to the common conception, we observed that central memory αß CD8+ T cells circulate with slower kinetics than naïve cells. Our results show that, similar to αß T cells, γδ T cells can acquire distinct migratory properties during their development and differentiation and reveal unexpected intricacies of T cell migratory patterns.

Absorbing one-dimensional planar photonic crystal for amorphous silicon solar cell.

We report on the absorption of a 100nm thick hydrogenated amorphous silicon layer patterned as a planar photonic crystal (PPC), using laser holography and reactive ion etching. Compared to an unpatterned layer, electromagnetic simulation and optical measurements both show a 50% increase of the absorption over the 0.38-0.75micron spectral range, in the case of a one-dimensional PPC. Such absorbing photonic crystals, combined with transparent and conductive layers, may be at the basis of new photovoltaic solar cells.

Stabilization and treatment of dental avulsions and fractures by emergency physicians using just-in-time training.

STUDY OBJECTIVE: The objective of this investigation is to use a dental simulation model to compare splinting and bandaging methods for managing tooth avulsions and fractures, as measured by dentist evaluators for quality and time to complete each stabilization procedure. METHODS: This was a randomized crossover study comparing 3 splinting techniques for managing a traumatically avulsed tooth (periodontal pack, wire, and bondable reinforcement ribbon) and 2 bandage techniques for managing a fractured tooth (calcium hydroxide paste and light-cured composite). After viewing a Just-in-Time training video, a convenience sample of emergency physicians performed the 5 stabilization techniques on dental models containing extracted teeth embedded in clay to simulate a segment of the human dentition. Data collected included time to complete each procedure, the evaluation of dentists about whether the procedure was performed satisfactorily or unsatisfactorily, and the ranking of dentists' and participants' preferred technique. RESULTS: Twenty-five emergency physicians participated in the study: 17 residents, 2 pediatric emergency medicine fellows, and 6 attending physicians. Reported median time, as well as minimum and maximum times to complete each splinting technique for an avulsed tooth, was as follows: periodontal pack 4.4 minutes (2.5 to 6.5 minutes), wire 8.6 minutes (5.8 to 12.9 minutes), and bondable reinforcement ribbon 8.9 minutes (5.6 to 15 minutes). Median time (and minimum and maximum times) to complete each protective bandaging technique for a fractured tooth was calcium hydroxide paste 4.6 minutes (3 to 9.6 minutes) and light-cured composite 7.1 minutes (5.5 to 14.1 minutes). When asked to choose a preferred splinting and bandaging technique according to the performance of the physicians, the dentists chose the bondable reinforcement ribbon 96% (24/25) and the light-cured composite 100% (25/25) of the time. Study participants had no measurable or agreeable preference for a particular splinting or bandaging technique. CONCLUSION: The results of this study suggest that of the stabilization procedures completed by emergency physicians, dentists preferred the bondable reinforcement ribbon for managing an avulsed tooth and the light-cured composite technique for managing a fractured tooth over the commonly taught and more frequently used procedures in emergency medicine.

Absorption enhancement using photonic crystals for silicon thin film solar cells.

We propose a design that increases significantly the absorption of a thin layer of absorbing material such as amorphous silicon. This is achieved by patterning a one-dimensional photonic crystal (1DPC) in this layer. Indeed, by coupling the incident light into slow Bloch modes of the 1DPC, we can control the photon lifetime and then, enhance the absorption integrated over the whole solar spectrum. Optimal parameters of the 1DPC maximize the integrated absorption in the wavelength range of interest, up to 45% in both S and P polarization states instead of 33% for the unpatterned, 100 nm thick amorphous silicon layer. Moreover, the absorption is tolerant with respect to fabrication errors, and remains relatively stable if the angle of incidence is changed.