No abstract

Background Docosahexaenoic acid (DHA) supplementation is beneficial for several chronic diseases; however, its effect on immune regulation is still debated. Given the prevalence of cytomegalovirus (CMV) infection and because natural killer (NK) cells are a component of innate immunity critical for controlling CMV infection, the current study explored the effect of a DHA-enriched diet on susceptibility to murine (M) CMV infection and the NK cell effector response to MCMV infection. Results Male C57BL/6 mice fed a control or DHA-enriched diet for 3 weeks were infected with MCMV and sacrificed at the indicated time points postinfection. Compared with control mice, DHA-fed mice had higher liver and spleen viral loads at day 7 postinfection, but final MCMV clearance was not affected. The total numbers of NK cells and their terminal mature cell subset (KLRG1+ and Ly49H+ NK cells) were reduced compared with those in control mice at day 7 postinfection but not day 21. DHA feeding resulted in higher IFN-γ and granzyme B expression in splenic NK cells at day 7 postinfection. A mechanistic analysis showed that the splenic NK cells of DHA-fed mice had enhanced glucose uptake, increased CD71 and CD98 expression, and higher mitochondrial mass than control mice. In addition, DHA-fed mice showed reductions in the total numbers and activation levels of CD4+ and CD8+ T cells. Conclusions These results suggest that DHA supplementation represses the early response to CMV infection but preserves NK cell effector functions by improving mitochondrial activity, which may play critical roles in subsequent MCMV clearance.

purity, bandgap-tunable light emission, [2] and long exciton transport lengths. [3] These outstanding optoelectronic properties make them attractive for light-emitting applications, such as those for luminescent solar cells, [4] lasers, [5] and perovskite light-emitting diodes (PeLEDs). [6] These devices have made notable progress in recent years, given the continuous efforts of researchers, especially for PeLEDs. Benefiting from suppressing nonradiative recombination [6a,7] and device structure optimization, [8] near-infrared PeLEDs have witnessed a sharp increase in external quantum efficiency (EQE), going from 0.76% [9] to >20%. [6b,7,8,10] Despite an impressive success, most PeLEDs still face a sizable challenge in the efficiency rolloff at high injection current density, thus restricting the realization of high brightness (or radiance) PeLEDs. [11] Therefore, it is key to improving the device brightness (or radiance) by mitigating unwanted rolloff drops at high injection current density. With regards to the roll-off degradation for PeLEDs at high injection current density, many factors, including defect-induced ion migration, [12] electromigration, [13] Auger combination, [14] imbalance transport, [11,15] along with Joule heating [11,15] are thought to be responsible for this undesirable efficiency drop. The external quantum efficiency (EQE) of state-of-the-art near-infrared perovskite light-emitting diodes (PeLEDs) is now approaching the limit set by the out-coupling efficiency. However, there is plenty of room for enhancing these devices' radiance and the EQE roll-off. This work reports how conductive and passivating additives construct efficient high-radiance near-infrared PeLEDs with improved EQE roll-off. Specifically, the synergistic effect of 1,4-phenylenediacetic acid (PDA) and 5-aminovaleric acid (5-AVA) is used to regulate the quality of the perovskite emissive layer, thereby enhancing the rolloff threshold of injection currents (a value at which the device EQE or radiance starts degrading). According to in situ structural evolution analyses from the perovskite precursor to the perovskite crystal, the presence of PDA within the perovskite precursor solution can produce an intermediate phase with 5-AVA and formanmidinium cation, which can retard the perovskite nucleation and crystal growth, leading to improved perovskite film quality. The resulting champion PeLED delivers among the highest radiance of 505 W sr −1 m −2 and a peak EQE of 17.56%. More importantly, the improved PeLED shows a well-retained radiance of 80% at a current injection density of up to ≈1800 mA cm −1 , opening a new avenue for high-radiance PeLEDs with improved roll-off degradation.