Long-term retention of antigens in germinal centers is controlled by the spatial organization of the follicular dendritic cell network.

Germinal centers (GCs) require sustained availability of antigens to promote antibody affinity maturation against pathogens and vaccines. A key source of antigens for GC B cells are immune complexes (ICs) displayed on follicular dendritic cells (FDCs). Here we show that FDC spatial organization regulates antigen dynamics in the GC. We identify heterogeneity within the FDC network. While the entire light zone (LZ) FDC network captures ICs initially, only the central cells of the network function as the antigen reservoir, where different antigens arriving from subsequent immunizations colocalize. Mechanistically, central LZ FDCs constitutively express subtly higher CR2 membrane densities than peripheral LZ FDCs, which strongly increases the IC retention half-life. Even though repeated immunizations gradually saturate central FDCs, B cell responses remain efficient because new antigens partially displace old ones. These results reveal the principles shaping antigen display on FDCs during the GC reaction.

Salivary IgA and vimentin differentiate in vitro SARS-CoV-2 infection: A study of 290 convalescent COVID-19 patients.

SARS-CoV-2 initially infects cells in the nasopharynx and oral cavity. The immune system at these mucosal sites plays a crucial role in minimizing viral transmission and infection. To develop new strategies for preventing SARS-CoV-2 infection, this study aimed to identify proteins that protect against viral infection in saliva. We collected 551 saliva samples from 290 healthcare workers who had tested positive for COVID-19, before vaccination, between June and December 2020. The samples were categorized based on their ability to block or enhance infection using in vitro assays. Mass spectrometry and enzyme-linked immunosorbent assay experiments were used to identify and measure the abundance of proteins that specifically bind to SARS-CoV-2 antigens. Immunoglobulin (Ig)A specific to SARS-CoV-2 antigens was detectable in over 83% of the convalescent saliva samples. We found that concentrations of anti-receptor-binding domain IgA >500 pg/µg total protein in saliva correlate with reduced viral infectivity in vitro. However, there is a dissociation between the salivary IgA response to SARS-CoV-2, and systemic IgG titers in convalescent COVID-19 patients. Then, using an innovative technique known as spike-baited mass spectrometry, we identified novel spike-binding proteins in saliva, most notably vimentin, which correlated with increased viral infectivity in vitro and could serve as a therapeutic target against COVID-19.

[Evolution of the incidence and survival of bronchogenic carcinoma in the province of Castellón (Spain) from 2004 to 2017.] / Evolución de la incidencia y supervivencia del carcinoma broncogénico en la provincia de Castellón en el periodo de tiempo 2004-2017.

OBJECTIVE: Bronchogenic carcinoma (BC) is the second most frequent worldwide and the most lethal tumour in both sexes. Its incidence varies not only among countries but also among different areas of the same country. So, the aim of this work was to analyse the evolution of its incidence and survival in the province of Castellón from 2004 to 2017 and to compare them with those of de rest of the country. METHODS: A retrospective observational study was carried out from patients diagnosed with BC and registered in the Castellón Tumour Register from 2004 to 2017. Survival was estimated using the Kaplan-Meier method whereas to estimate the relationship among different variables both the chi-square and ANOVA test were used. RESULTS: 4,346 cases were diagnosed, whose mean age was 67.5±11.3 years, 85.2% men, the most frequent histological types were adenocarcinoma (28.3%) and epidermoid carcinoma (25.1%). The gross global incidence was 53.4 cases/105 inhabitants, 90.9 cases/105 men and 15.7 cases/105 women. Median global survival at five years was 12.7%, 12% in men and 18.4% in women. CONCLUSIONS: The global incidence of BC in Castellón is lower than the national one, having remained stable in men while it is double in women. Global survival at five years is less than 15%, being higher in women than in men, nevertheless it increases compared to that of previous studies.

OBJETIVO: El carcinoma broncogénico (CB) es el segundo tumor más frecuente a nivel mundial y el más letal en ambos sexos. Su incidencia varía, no sólo entre países, sino también entre diferentes zonas de un mismo país. Por tanto, el objetivo de este trabajo fue analizar la evolución de su incidencia y la supervivencia en la provincia de Castellón desde 2004 hasta 2017, y compararlas con las del resto del país. METODOS: Se realizó un estudio observacional retrospectivo en pacientes diagnosticados de CB e inscritos en el Registro de Tumores de Castellón desde 2004 hasta 2017. La supervivencia se estimó mediante el método de Kaplan-Meier, mientras que para estimar la relación entre distintas variables se utilizaron los test Chi-cuadrado y ANOVA. RESULTADOS: Se diagnosticaron 4.346 casos, con una edad media de 67,5±11,3 años, el 85,2% eran hombres, los tipos histológicos más frecuentes fueron adenocarcinoma (28,3%) y carcinoma epidermoide (25,1%). La incidencia global bruta fue de 53,4 casos/105 habitantes, con 90,9 casos/105 de hombres y 15,7 casos/105 de mujeres. La mediana de supervivencia global a los cinco años fue del 12,7%, siendo del 12% en hombres y del 18,4% en mujeres. CONCLUSIONES: La incidencia global de CB en Castellón es inferior a la nacional, habiéndose mantenido estable en hombres mientras que se duplica en mujeres. La supervivencia global a los cinco años es inferior al 15%, siendo mayor en mujeres que en hombres; no obstante, aumenta respecto a la reportada en estudios previos.

Cognitive-behavioral intervention via interactive multimedia online video game for active aging: study protocol for a randomized controlled trial.

BACKGROUND: Due to the progressive aging of the population, programs to promote active aging have been recommended. However, older adults have difficulty accessing them. Interventions administered through online video games may increase their accessibility, and complementing these with a smartphone app will likely increase adherence and allow for ongoing professional monitoring. The objective of this study is to evaluate the efficacy of a cognitive-behavioral intervention for active aging administered through an online interactive multimedia video game that includes a smartphone app companion. The secondary objectives are to analyze the moderators and mediators of the change in the outcome variables and to evaluate the adherence to the intervention. METHODS/DESIGN: A randomized controlled clinical trial will be conducted. Adults 45 years and older will be randomly assigned to a cognitive-behavioral intervention administered through an online multimedia video game that includes a smartphone app companion or to a control group that will receive online information on active aging (274 participants per group). The intervention will be administered in eight weekly 45-min modules. An investigator-blinded evaluation will be conducted using online self-administered tests at baseline, post-intervention, and 6- and 12-month follow-ups. The primary outcome will be mental health status as evaluated using the 36-item Short-Form Health Survey (SF-36) at post-intervention. Secondary outcomes will be emotional well-being, depressive symptoms, reinforcement, negative thoughts, self-reported memory, cognitive task performance, sleep hygiene behaviors, physical activity, eating habits, body mass index, social support, dropout, treatment adherence, and satisfaction with the intervention. DISCUSSION: If the results are favorable, this study would involve the development of the first evidence-based active aging promotion intervention based on a video game that includes a smartphone app companion, providing evidence on its efficacy, accessibility, and clinical utility. TRIAL REGISTRATION: ClinicalTrials.gov, NCT03643237. Registered 27 August 2018.

Myosin IIa Promotes Antibody Responses by Regulating B Cell Activation, Acquisition of Antigen, and Proliferation.

B cell responses are regulated by antigen acquisition, processing, and presentation to helper T cells. These functions are thought to depend on contractile activity of non-muscle myosin IIa. Here, we show that B cell-specific deletion of the myosin IIa heavy chain reduced the numbers of bone marrow B cell precursors and splenic marginal zone, peritoneal B1b, and germinal center B cells. In addition, myosin IIa-deficient follicular B cells acquired an activated phenotype and were less efficient in chemokinesis and extraction of membrane-presented antigens. Moreover, myosin IIa was indispensable for cytokinesis. Consequently, mice with myosin IIa-deficient B cells harbored reduced serum immunoglobulin levels and did not mount robust antibody responses when immunized. Altogether, these data indicate that myosin IIa is a negative regulator of B cell activation but a positive regulator of antigen acquisition from antigen-presenting cells and that myosin IIa is essential for B cell development, proliferation, and antibody responses.

B cells use mechanical energy to discriminate antigen affinities.

The generation of high-affinity antibodies depends on the ability of B cells to extract antigens from the surfaces of antigen-presenting cells. B cells that express high-affinity B cell receptors (BCRs) acquire more antigen and obtain better T cell help. However, the mechanisms by which B cells extract antigen remain unclear. Using fluid and flexible membrane substrates to mimic antigen-presenting cells, we showed that B cells acquire antigen by dynamic myosin IIa-mediated contractions that pull out and invaginate the presenting membranes. The forces generated by myosin IIa contractions ruptured most individual BCR-antigen bonds and promoted internalization of only high-affinity, multivalent BCR microclusters. Thus, B cell contractility contributes to affinity discrimination by mechanically testing the strength of antigen binding.

Directionality of electron-transfer reactions in photosystem I of prokaryotes: universality of the bidirectional electron-transfer model.

The electron-transfer (ET) reactions in photosystem I (PS I) of prokaryotes have been investigated in wild-type cells of the cyanobacterium Synechocystis sp. PCC 6803, and in two site-directed mutants in which the methionine residue of the reaction center subunits PsaA and PsaB, which acts as the axial ligand to the primary electron chlorophyll acceptor A(0), was substituted with histidine. Analysis by pulsed electron paramagnetic resonance spectroscopy at 100 K indicates the presence of two forms of the secondary spin-correlated radical pairs, which are assigned to [P(700)(+)A(1A)(-)] and [P(700)(+)A(1B)(-)], where A(1A) and A(1B) are the phylloquinone molecules bound to the PsaA and the PsaB reaction center subunits, respectively. Each of the secondary radical pair forms is selectively observed in either the PsaA-M688H or the PsaB-M668H mutant, whereas both radical pairs are observed in the wild type following reduction of the iron-sulfur cluster F(X), the intermediate electron acceptor between A(1) and the terminal acceptors F(A) and F(B). Analysis of the time and spectral dependence of the light-induced electron spin echo allows the resolution of structural differences between the [P(700)(+)A(1A)(-)] and [P(700)(+)A(1B)(-)] radical pairs. The interspin distance is 25.43 ± 0.01 Å for [P(700)(+)A(1A)(-)] and 24.25 ± 0.01 Å for [P(700)(+)A(1B)(-)]. Moreover, the relative orientation of the interspin vector is rotated by ~60° with respect to the g-tensor of the P(700)(+) radical. These estimates are in agreement with the crystallographic structural model, indicating that the cofactors bound to both reaction center subunits of prokaryotic PS I are actively involved in electron transport. This work supports the model that bidirectionality is a general property of type I reaction centers from both prokaryotes and eukaryotes, and contrasts with the situation for photosystem II and other type II reaction centers, in which ET is strongly asymmetric. A revised model that explains qualitatively the heterogeneity of ET reactions at cryogenic temperatures is discussed.

Analysis of the spin-polarized electron spin echo of the [P700+ A1-] radical pair of photosystem I indicates that both reaction center subunits are competent in electron transfer in cyanobacteria, green algae, and higher plants.

The decay of the light-induced spin-correlated radical pair [P700+ A1-] and the associated electron spin echo envelope modulation (ESEEM) have been studied in either thylakoid membranes, cellular membranes, or purified photosystem I prepared from the wild-type strains of Synechocystis sp. PCC 6803, Chlamydomonas reinhardtii, and Spinaceae oleracea. The decay of the spin-correlated radical pair is described in the wild-type membrane by two exponential components with lifetimes of 2-4 and 16-25 micros. The proportions of the two components can be altered by preillumination of the membranes in the presence of reductant at temperatures lower than 220 K, which leads to the complete reduction of the iron-sulfur electron acceptors F(A), F(B), and F(X) and partial photoaccumulation of the reduced quinone electron acceptor A1A-. The "out-of-phase" (OOP) ESEEM attributed to the [P700+ A1-] radical pair has been investigated in the three species as a function of the preillumination treatment. Values of the dipolar (D) and the exchange (J) interactions were extracted by time-domain fitting of the OOP-ESEEM. The results obtained in the wild-type systems are compared with two site-directed mutants of C. reinhardtii [Santabarbara et al. (2005) Biochemistry 44, 2119-2128], in which the spin-polarized signal on either the PsaA- or PsaB-bound electron transfer pathway is suppressed so that the radical pair formed on each electron transfer branch could be monitored selectively. This comparison indicates that when all of the iron-sulfur centers are oxidized, only the echo modulation associated with the A branch [P700+ A1A-] radical pair is observed. The reduction of the iron-sulfur clusters and the quinone A1 by preillumination treatment induces a shift in the ESEEM frequency. In all of the systems investigated this observation can be interpreted in terms of different proportions of the signal associated with the [P700+ A1A-] and [P700+ A1B-] radical pairs, suggesting that bidirectionality of electron transfer in photosystem I is a common feature of all species rather than being confined to green algae.