Disrupted Peyer's Patch Microanatomy in COVID-19 Including Germinal Centre Atrophy Independent of Local Virus.

Confirmed SARS-coronavirus-2 infection with gastrointestinal symptoms and changes in microbiota associated with coronavirus disease 2019 (COVID-19) severity have been previously reported, but the disease impact on the architecture and cellularity of ileal Peyer's patches (PP) remains unknown. Here we analysed post-mortem tissues from throughout the gastrointestinal (GI) tract of patients who died with COVID-19. When virus was detected by PCR in the GI tract, immunohistochemistry identified virus in epithelium and lamina propria macrophages, but not in lymphoid tissues. Immunohistochemistry and imaging mass cytometry (IMC) analysis of ileal PP revealed depletion of germinal centres (GC), disruption of B cell/T cell zonation and decreased potential B and T cell interaction and lower nuclear density in COVID-19 patients. This occurred independent of the local viral levels. The changes in PP demonstrate that the ability to mount an intestinal immune response is compromised in severe COVID-19, which could contribute to observed dysbiosis.

Two subsets of human marginal zone B cells resolved by global analysis of lymphoid tissues and blood.

B cells generate antibodies that are essential for immune protection, but their subgroups are poorly defined. Here, we perform undirected deep profiling of B cells in matched human lymphoid tissues from deceased transplant organ donors and blood. In addition to identifying unanticipated features of tissue-based B cell differentiation, we resolve two subsets of marginal zone B (MZB) cells differing in cell surface and transcriptomic profiles, clonal relationships to other subsets, enrichment of genes in the NOTCH pathway, distribution bias within splenic marginal zone microenvironment, and immunoglobulin repertoire diversity and hypermutation frequency. Each subset is present in spleen, gut-associated lymphoid tissue, mesenteric lymph nodes, and blood. MZB cells and the lineage from which they are derived are depleted in lupus nephritis. Here, we show that this depletion is of only one MZB subset. The other remains unchanged as a proportion of total B cells compared with health. Thus, it is important to factor MZB cell heterogeneity into studies of human B cell responses and pathology.

Immunogenomics of Colorectal Cancer Response to Checkpoint Blockade: Analysis of the KEYNOTE 177 Trial and Validation Cohorts.

BACKGROUND & AIMS: Colorectal cancer (CRC) shows variable response to immune checkpoint blockade, which can only partially be explained by high tumor mutational burden (TMB). We conducted an integrated study of the cancer tissue and associated tumor microenvironment (TME) from patients treated with pembrolizumab (KEYNOTE 177 clinical trial) or nivolumab to dissect the cellular and molecular determinants of response to anti- programmed cell death 1 (PD1) immunotherapy. METHODS: We selected multiple regions per tumor showing variable T-cell infiltration for a total of 738 regions from 29 patients, divided into discovery and validation cohorts. We performed multiregional whole-exome and RNA sequencing of the tumor cells and integrated these with T-cell receptor sequencing, high-dimensional imaging mass cytometry, detection of programmed death-ligand 1 (PDL1) interaction in situ, multiplexed immunofluorescence, and computational spatial analysis of the TME. RESULTS: In hypermutated CRCs, response to anti-PD1 immunotherapy was not associated with TMB but with high clonality of immunogenic mutations, clonally expanded T cells, low activation of Wnt signaling, deregulation of the interferon gamma pathway, and active immune escape mechanisms. Responsive hypermutated CRCs were also rich in cytotoxic and proliferating PD1+CD8 T cells interacting with PDL1+ antigen-presenting macrophages. CONCLUSIONS: Our study clarified the limits of TMB as a predictor of response of CRC to anti-PD1 immunotherapy. It identified a population of antigen-presenting macrophages interacting with CD8 T cells that consistently segregate with response. We therefore concluded that anti-PD1 agents release the PD1-PDL1 interaction between CD8 T cells and macrophages to promote cytotoxic antitumor activity.

Spatiotemporal segregation of human marginal zone and memory B cell populations in lymphoid tissue.

Human memory B cells and marginal zone (MZ) B cells share common features such as the expression of CD27 and somatic mutations in their IGHV and BCL6 genes, but the relationship between them is controversial. Here, we show phenotypic progression within lymphoid tissues as MZ B cells emerge from the mature naïve B cell pool via a precursor CD27-CD45RBMEM55+ population distant from memory cells. By imaging mass cytometry, we find that MZ B cells and memory B cells occupy different microanatomical niches in organised gut lymphoid tissues. Both populations disseminate widely between distant lymphoid tissues and blood, and both diversify their IGHV repertoire in gut germinal centres (GC), but nevertheless remain largely clonally separate. MZ B cells are therefore not developmentally contiguous with or analogous to classical memory B cells despite their shared ability to transit through GC, where somatic mutations are acquired.

Outcome of women versus men with ventricular tachyarrhythmias treated with the implantable cardioverter defibrillator.

INTRODUCTION: Important sex differences in the incidence and outcome of patients with ischemic heart disease, the leading cause of ventricular tachyarrhythmias, have been identified. Implantable cardioverter defibrillator (ICD) therapy has become the treatment of choice for patients with ventricular tachycardia (VT) and ventricular fibrillation (VF), but little is known about gender differences in the outcome of ICD-treated patients. METHODS AND RESULTS: In this retrospective study, we compared arrhythmic events and survival of 376 women and 1,654 men treated with an ICD as part of prospective evaluations of transvenous devices or lead systems. Women were younger (62+/-14 years vs 65+/-12 years, P = 0.0005), had higher left ventricular ejection fraction (0.36+/-0.15 vs 0.32+/-0.13, P < 0.0001), were more likely to present with VF (34% vs 19%, P < 0.001), and had lower implantation defibrillation threshold (11+/-6 vs 13+/-6 J, P < 0.0001). Implant complication rates were similar in men and women (2.6% vs 3.5%, P = 0.46). The 1-year and 2-year cumulative rates of appropriate ICD therapies were 31.4% and 38.4% for men and 32.6% and 40.8% for women, respectively (P = 0.63). The unadjusted 1-year and 2-year cumulative survival rates were 95.6% and 93.7% for men and 95.7% and 94.3% for women, respectively (P = 0.98). Adjusted total (P = 0.61), sudden (P = 0.82), and cardiac (P = 0.34) death-free survivals also were similar in men and women. CONCLUSION: Despite clinical differences suggesting women are at lower risk than men, men and women with VT/VF who are treated with an ICD have similar arrhythmic event and survival rates. These factors should be considered when determining risk and prescription of ICD therapy for women.