ABSTRACT Background Serological tests are crucial tools for assessments of SARS-CoV-2 exposure, infection and potential immunity. Their appropriate use and interpretation require accurate assay performance data. Method We conducted an evaluation of 10 lateral flow assays (LFAs) and two ELISAs to detect anti-SARS-CoV-2 antibodies. The specimen set comprised 128 plasma or serum samples from 79 symptomatic SARS-CoV-2 RT-PCR-positive individuals; 108 pre-COVID-19 negative controls; and 52 recent samples from individuals who underwent respiratory viral testing but were not diagnosed with Coronavirus Disease 2019 (COVID-19). Samples were blinded and LFA results were interpreted by two independent readers, using a standardized intensity scoring system. Results Among specimens from SARS-CoV-2 RT-PCR-positive individuals, the percent seropositive increased with time interval, peaking at 81.8-100.0% in samples taken >20 days after symptom onset. Test specificity ranged from 84.3-100.0% in pre-COVID-19 specimens. Specificity was higher when weak LFA bands were considered negative, but this decreased sensitivity. IgM detection was more variable than IgG, and detection was highest when IgM and IgG results were combined. Agreement between ELISAs and LFAs ranged from 75.7-94.8%. No consistent cross-reactivity was observed. Conclusion Our evaluation showed heterogeneous assay performance. Reader training is key to reliable LFA performance, and can be tailored for survey goals. Informed use of serology will require evaluations covering the full spectrum of SARS-CoV-2 infections, from asymptomatic and mild infection to severe disease, and later convalescence. Well-designed studies to elucidate the mechanisms and serological correlates of protective immunity will be crucial to guide rational clinical and public health policies.
Intravital microscopy has enabled the study of immune dynamics in the pulmonary microvasculature, but many key events remain unseen because they occur in deeper lung regions. We therefore developed a technique for stabilized intravital imaging of bronchovascular cuffs and collecting lymphatics surrounding pulmonary veins in mice. Intravital imaging of pulmonary lymphatics revealed ventilation dependence of steady-state lung lymph flow and ventilation-independent lymph flow during inflammation. We imaged the rapid exodus of migratory dendritic cells through lung lymphatics following inflammation and measured effects of pharmacologic and genetic interventions targeting chemokine signaling. Intravital imaging also captured lymphatic immune surveillance of lung-metastatic cancers and lymphatic metastasis of cancer cells. To our knowledge, this is the first imaging of lymph flow and leukocyte migration through intact pulmonary lymphatics. This approach will enable studies of protective and maladaptive processes unfolding within the lungs and in other previously inaccessible locations.
Lymph nodes (LNs), Peyer’s patches (PPs), and the spleen are command centers for the adaptive immune system, bringing together Ags and immune cells for the initiation of antipathogen offensives. The anatomy of these organs has been studied for over 100 years, and their organization into thymus-
The tumor necrosis factor receptor superfamily member HVEM is one of the most frequently mutated surface proteins in germinal center (GC)-derived B cell lymphomas. We found that HVEM deficiency increased B cell competitiveness during pre-GC and GC responses. The immunoglobulin (Ig) superfamily protein BTLA regulated HVEM-expressing B cell responses independently of B-cell-intrinsic signaling via HVEM or BTLA. BTLA signaling into T cells through the phosphatase SHP1 reduced T cell receptor (TCR) signaling and preformed CD40 ligand mobilization to the immunological synapse, thus diminishing the help delivered to B cells. Moreover, T cell deficiency in BTLA cooperated with B cell Bcl-2 overexpression, leading to GC B cell outgrowth. These results establish that HVEM restrains the T helper signals delivered to B cells to influence GC selection outcomes, and they suggest that BTLA functions as a cell-extrinsic suppressor of GC B cell lymphomagenesis.
Summary: As we travel into a new century, confronted with new infectious diseases and bioweapon threats, with surgeons continuing to push the boundaries of what is transplantable, and with gene therapists working on ways to remedy a myriad of genetic diseases, the need for improved methods to augment and suppress immune function is paramount. The recent discovery that a novel immunosuppressant works by blocking lymphocyte egress from lymphoid organs provides a compelling example of how improved understanding of lymphoid organ function will contribute to future drug development and human health. This volume brings together reviews from leaders in the field of thymus and secondary lymphoid organ biology, including discussions on the roles of transcriptional regulators Foxn1, retinoid‐related orphan receptor γ and nuclear factor‐κB in lymphoid organ development, the function of lymphotoxin and other cytokines in lymphoid tissue organization, the guidance activity of chemokines in a multitude of immune cell‐positioning events, the mechanism of action of the immunosuppressant FTY720, and the application of two‐photon laser scanning microscopy to reveal the dynamic behavior of lymphoid cells in the depths of these essential tissues.
(Immunity 39, 912–924; November 14, 2013) In the version of this paper originally published online, Tables S1–S3 were omitted. The Supplemental Information has now been corrected, and the journal regrets the error. Germinal Center Centroblasts Transition to a Centrocyte Phenotype According to a Timed Program and Depend on the Dark Zone for Effective SelectionBannard et al.ImmunityOctober 31, 2013In BriefGerminal center (GC) B cells cycle between the dark zone (DZ) and light zone (LZ) during antibody affinity maturation. Whether this movement is necessary for GC function has not been tested. Here we show that CXCR4-deficient GC B cells, which are restricted to the LZ, are gradually outcompeted by WT cells indicating an essential role for DZ access. Remarkably, the transition between DZ centroblast and LZ centrocyte phenotypes occurred independently of positioning. However, CXCR4-deficient cells carried fewer mutations and were overrepresented in the CD73+ memory compartment. Full-Text PDF Open Access
Abstract Dendritic cells (DCs) play an essential role in the development of type 2 allergic immunity by presenting allergens to cognate naïve T cells inducing production of IL-4 thus priming type 2 T helper (Th2) cells. However, the molecular mechanisms underlying this function are poorly understood. We found that mice deficient in the expression of MARCH1 ubiquitin ligase in DCs were completely resistant to developing Th2 cell inflammation and eosinophilia upon airway exposure to house dust mite allergens. These mice exhibited normal expansion of allergen-specific CD4+ T cells and normal production of IFN-γ from the T cells but demonstrated a significant defect in the production of IL-4, suggesting a specific role of MARCH1 in DC priming of Th2 cells. Remarkably, mice lacking the ubiquitin acceptor amino acids of the MARCH1 substrates, MHCII and CD86, phenocopied MARCH1-deficient mice, indicating that MARCH1 promotes Th2 cell priming by mediating ubiquitination of MHCII and CD86. Ubiquitination of MHCII was important for CD11b+ DCs to transport respiratory allergens to the mediastinal lymph node whereas ubiquitination of CD86 as well as MHCII was involved in transcriptional reprograming of these DCs. In conclusion, dendritic cells depend on ubiquitination of MHCII and CD86 to condition themselves to effectively migrate to the draining lymph node and induce production of IL-4 from allergen-specific naïve CD4+ T cells.
Lymphocyte egress from lymph nodes (LNs) is dependent on sphingosine-1-phosphate (S1P), but the cellular source of this S1P is not defined. We generated mice that expressed Cre from the lymphatic vessel endothelial hyaluronan receptor 1 (Lyve-1) locus and that showed efficient recombination of loxP-flanked genes in lymphatic endothelium. We report that mice with Lyve-1 CRE-mediated ablation of sphingosine kinase (Sphk) 1 and lacking Sphk2 have a loss of S1P in lymph while maintaining normal plasma S1P. In Lyve-1 Cre+ Sphk-deficient mice, lymphocyte egress from LNs and Peyer's patches is blocked. Treatment with pertussis toxin to overcome Gαi-mediated retention signals restores lymphocyte egress. Furthermore, in the absence of lymphatic Sphks, the initial lymphatic vessels in nonlymphoid tissues show an irregular morphology and a less organized vascular endothelial cadherin distribution at cell–cell junctions. Our data provide evidence that lymphatic endothelial cells are an in vivo source of S1P required for lymphocyte egress from LNs and Peyer's patches, and suggest a role for S1P in lymphatic vessel maturation.
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