Macroautophagy in lymphatic endothelial cells inhibits T cell–mediated autoimmunity

Lymphatic endothelial cells (LECs) present peripheral tissue antigens to induce T cell tolerance. In addition, LECs are the main source of sphingosine-1-phosphate (S1P), promoting naive T cell survival and effector T cell exit from lymph nodes (LNs). Autophagy is a physiological process essential for cellular homeostasis. We investigated whether autophagy in LECs modulates T cell activation in experimental arthritis. Whereas genetic abrogation of autophagy in LECs does not alter immune homeostasis, it induces alterations of the regulatory T cell (T reg cell) population in LNs from arthritic mice, which might be linked to MHCII-mediated antigen presentation by LECs. Furthermore, inflammation-induced autophagy in LECs promotes the degradation of Sphingosine kinase 1 (SphK1), resulting in decreased S1P production. Consequently, in arthritic mice lacking autophagy in LECs, pathogenic Th17 cell migration toward LEC-derived S1P gradients and egress from LNs are enhanced, as well as infiltration of inflamed joints, resulting in exacerbated arthritis. Our results highlight the autophagy pathway as an important regulator of LEC immunomodulatory functions in inflammatory conditions.     

Joint Trauma System,Defense Committee on Trauma,and Armed Services Blood Program consensus statement on whole blood

Hemorrhage is the most common mechanism of death in battlefield casualties with potentially survivable injuries. There is evidence that early blood product transfusion saves lives among combat casualties. When compared to component therapy, fresh whole blood transfusion improves outcomes in military settings. Cold-stored whole blood also improves outcomes in trauma patients. Whole blood has the advantage of providing red cells, plasma, and platelets together in a single unit, which simplifies and speeds the process of resuscitation, particularly in austere environments. The Joint Trauma System, the Defense Committee on Trauma, and the Armed Services Blood Program endorse the following: (1) whole blood should be used to treat hemorrhagic shock; (2) low-titer group O whole blood is the resuscitation product of choice for the treatment of hemorrhagic shock for all casualties at all roles of care; (3) whole blood should be available within 30 min of casualty wounding, on all medical evacuation platforms, and at all resuscitation and surgical team locations; (4) when whole blood is not available, component therapy should be available within 30 min of casualty wounding; (5) all prehospital medical providers should be trained and logistically supported to screen donors, collect fresh whole blood from designated donors, transfuse blood products, recognize and treat transfusion reactions, and complete the minimum documentation requirements; (6) all deploying military personnel should undergo walking blood bank prescreen laboratory testing for transfusion transmitted disease immediately prior to deployment. Those who are blood group O should undergo anti-A/anti-B antibody titer testing.     

Age-determined expression of priming protease TMPRSS2 and localization of SARS-CoV-2 in lung epithelium

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) novel coronavirus 2019 (COVID-19) global pandemic has led to millions of cases and hundreds of thousands of deaths. While older adults appear at high risk for severe disease, hospitalizations and deaths due to SARS-CoV-2 among children have been relatively rare. Integrating single-cell RNA sequencing (scRNA-seq) of developing mouse lung with temporally resolved immunofluorescence in mouse and human lung tissue, we found that expression of SARS-CoV-2 Spike protein primer TMPRSS2 was highest in ciliated cells and type I alveolar epithelial cells (AT1), and TMPRSS2 expression increased with aging in mice and humans. Analysis of autopsy tissue from fatal COVID-19 cases detected SARS-CoV-2 RNA most frequently in ciliated and secretory cells in airway epithelium and AT1 cells in peripheral lung. SARS-CoV-2 RNA was highly colocalized in cells expressing TMPRSS2. Together, these data demonstrate the cellular spectrum infected by SARS-CoV-2 in lung epithelium and suggest that developmental regulation of TMPRSS2 may underlie the relative protection of infants and children from severe respiratory illness.     

Broad and potent neutralizing human antibodies to tick-borne flaviviruses protect mice from disease

Tick-borne encephalitis virus (TBEV) is an emerging human pathogen that causes potentially fatal disease with no specific treatment. Mouse monoclonal antibodies are protective against TBEV, but little is known about the human antibody response to infection. Here, we report on the human neutralizing antibody response to TBEV in a cohort of infected and vaccinated individuals. Expanded clones of memory B cells expressed closely related anti-envelope domain III (EDIII) antibodies in both groups of volunteers. However, the most potent neutralizing antibodies, with IC₅₀s below 1 ng/ml, were found only in individuals who recovered from natural infection. These antibodies also neutralized other tick-borne flaviviruses, including Langat, louping ill, Omsk hemorrhagic fever, Kyasanur forest disease, and Powassan viruses. Structural analysis revealed a conserved epitope near the lateral ridge of EDIII adjoining the EDI–EDIII hinge region. Prophylactic or early therapeutic antibody administration was effective at low doses in mice that were lethally infected with TBEV.     

Subtle changes in TCRα CDR1 profoundly increase the sensitivity of CD4 T cells

Changes in the peptide and MHC molecules have been extensively examined for how they alter T cell activation, but many fewer studies have examined the TCR. Structural studies of how TCR differences alter T cell specificity have focused on broad variation in the CDR3 loops. However, changes in the CDR1 and 2 loops can also alter TCR recognition of pMHC. In this study we focus on two mutations in the CDR1α loop of the TCR that increased the affinity of a TCR for agonist Hb(64-76)/I-E^k by increasing the on-rate of the reaction. These same mutations also conferred broader recognition of altered peptide ligands. TCR transgenic mice expressing the CDR1α mutations had altered thymic selection, as most of the T cells were negatively selected compared to T cells expressing the wildtype TCR. The few T cells that escaped negative selection and were found in the periphery were rendered anergic, thereby avoiding autoimmunity. T cells with the CDR1α mutations were completely deleted in the presence of Hb(64-76) as an endogenous peptide. Interestingly, the wildtype T cells were not eliminated, identifying a threshold affinity for negative selection where a 3-fold increase in affinity is the difference between incomplete and complete deletion. Overall, these studies highlight how small changes in the TCR can increase the affinity of TCR:pMHC but with the consequences of skewing selection and producing an unresponsive T cell.     

High molecular weight complex analysis of Epstein–Barr virus Latent Membrane Protein 1 (LMP-1): Structural insights into LMP-1's homo-oligomerization and lipid raft association

LMP-1 is a constitutively active Tumor Necrosis Factor Receptor analog encoded by Epstein–Barr virus. LMP-1 activation correlates with oligomerization and raft localization, but direct evidence of LMP-1 oligomers is limited. We report that LMP-1 forms multiple high molecular weight native LMP-1 complexes when analyzed by BN-PAGE, the largest of which are enriched in detergent resistant membranes. The largest of these high molecular weight complexes are not formed by purified LMP-1 or by loss of function LMP-1 mutants. Consistent with these results we find a dimeric form of LMP-1 that can be stabilized by disulfide crosslinking. We identify cysteine 238 in the C-terminus of LMP-1 as the crosslinked cysteine. Disulfide crosslinking occurs post-lysis but the dimer can be crosslinked in intact cells with membrane permeable crosslinkers. LMP-1/C238A retains wild type LMP-1 NF-κB activity. LMP-1's TRAF binding, raft association and oligomerization are associated with the dimeric form of LMP-1. Our results suggest the possibility that the observed dimeric species results from inter-oligomeric crosslinking of LMP-1 molecules in adjacent core LMP-1 oligomers.     

Short-term memory,working memory,and syntactic comprehension in aphasia

Sixty-one people with aphasia were tested on 10 tests of short-term memory (STM) and for the ability to use syntactic structure to determine the meanings of 11 types of sentences in three tasks—object manipulation, picture matching, and picture matching with self-paced listening. Multilevel models showed relationships between measures of the ability to retain and manipulate item and order information in STM and accuracy and reaction time (RT), and a greater relationship between these STM measures and accuracy and RT for several more complex sentence types in individual tasks. There were no effects of measures of STM that reflect the use of phonological codes or rehearsal on comprehension. There was only one effect of STM measures on self-paced listening times. There were double dissociations between performance on STM and individual comprehension tasks, indicating that normal STM is not necessary to perform normally on these tasks. The results are most easily related to the view that STM plays a facilitatory role in supporting the use of the products of the comprehension process to accomplish operations related to tasks.