Although clonal neo-antigen burden is associated with improved response to immune therapy, the functional basis for this remains unclear. Here we study this question in a novel controlled mouse melanoma model that enables us to explore the effects of intra-tumor heterogeneity (ITH) on tumor aggressiveness and immunity independent of tumor mutational burden. Induction of UVB-derived mutations yields highly aggressive tumors with decreased anti-tumor activity. However, single-cell-derived tumors with reduced ITH are swiftly rejected. Their rejection is accompanied by increased T cell reactivity and a less suppressive microenvironment. Using phylogenetic analyses and mixing experiments of single-cell clones, we dissect two characteristics of ITH: the number of clones forming the tumor and their clonal diversity. Our analysis of melanoma patient tumor data recapitulates our results in terms of overall survival and response to immune checkpoint therapy. These findings highlight the importance of clonal mutations in robust immune surveillance and the need to quantify patient ITH to determine the response to checkpoint blockade.

Experimental autoimmune encephalomyelitis (EAE) is a widely used model of multiple sclerosis. In NOD mice, EAE develops as a relapsing–remitting disease that transitions to a chronic progressive disease, making the NOD model the only mouse model that recapitulates the full clinical disease course observed in most multiple sclerosis patients. We have generated a TCR transgenic mouse that expresses the α- and β-chains of a myelin oligodendrocyte glycoprotein (MOG) 35–55–reactive TCR (1C6) on the NOD background. 1C6 TCR transgenic mice spontaneously generate both CD4⁺ and CD8⁺ T cells that recognize MOG and produce proinflammatory cytokines, allowing for the first time to our knowledge the simultaneous examination of myelin-reactive CD4⁺ and CD8⁺ T cells in the same host. 1C6 CD8⁺ T cells alone can induce optic neuritis and mild EAE with delayed onset; however, 1C6 CD4⁺ T cells alone induce severe EAE and predominate in driving disease when both cell types are present. When 1C6 mice are crossed with mice bearing an IgH specific for MOG, the mice develop spontaneous EAE with high incidence, but surprisingly the disease pattern does not resemble the neuromyelitis optica-like disease observed in mice bearing CD4⁺ T cells and B cells reactive to MOG on the C57BL/6 background. Collectively, our data show that although myelin-reactive CD8⁺ T cells contribute to disease, disease is primarily driven by myelin-reactive CD4⁺ T cells and that the coexistence of myelin-reactive T and B cells does not necessarily result in a distinct pathological phenotype.

Protective immune responses depend on the formation of immune synapses between T cells and antigen-presenting cells (APCs). The two main LFA-1 ligands, ICAM-1 and ICAM-2, are co-expressed on many cell types, including APCs and blood vessels. Although these molecules were suggested to be key players in immune synapses studied in vitro, their contribution to helper T cell priming in vivo is unclear. Here, we used transgenic mice and intravital imaging to examine the role of dendritic cell (DC) ICAM-1 and ICAM-2 in naive CD4 T cell priming and differentiation in skin-draining lymph nodes. Surprisingly, ICAM deficiency on endogenous CD40-stimulated lymph node DCs did not impair their ability to arrest and prime CD4 lymphocyte activation and differentiation into Th1 and Tfh effectors. Thus, functional T cell receptor (TCR)-specific helper T cell synapses with antigen-presenting DCs and subsequent proliferation and early differentiation into T effectors do not require LFA-1-mediated T cell adhesiveness to DC ICAMs.

The pulmonary vasculature constitutively expresses the integrin lymphocyte function‐associated antigen‐1 ligands intercellular adhesion molecule (ICAM)‐1 and ‐2. In this study, effector T cells were temporarily entrapped by the lung vasculature on their way to inflamed lymph nodes, and this entrapment was strongly reduced in ICAM‐1 and ‐2 double‐deficient mice (79 and 86% reduction for CD8 ⁺ and CD4 ⁺ effectors, respectively, compared with wild‐type mice). Although the pulmonary vasculature has been suggested to be masked by the heparan sulfate‐containing glycocalyx, which is susceptible to heparanase‐mediated shedding, lung and lymphocyte heparanase have been found to be unnecessary for this entrapment. Systemic LPS induced rapid neutrophil entrapment in the lung vasculature, but in contrast to T‐cell entrapment, this sequestration was ICAM‐1, ICAM‐2, and heparanase independent. Furthermore, neutrophil migration into the bronchoalveolar space induced by LPS inhalation and LPS‐induced leakage of red blood cells into this space were not dependent on lung ICAMs or heparanase activity. Nevertheless, heparanase was critical for neutrophil accumulation in smoke‐exposed lungs. Our results indicate that, whereas T cells use ICAM‐1 and ‐2 for temporary pulmonary entrapment, neutrophils get sequestered and extravasate into inflamed lungs independent of ICAMs. This is the first demonstration that the pulmonary vasculature is differentially recognized by T cells and neutrophils.—Petrovich, E., Feigelson, S. W., Stoler‐Barak, L., Hatzav, M., Solomon, A., Bar‐Shai, A., Ilan, N., Li, J.‐P., Engelhardt, B., Vlodavsky, I., Alon, R. Lung ICAM‐1 and ICAM‐2 support spontaneous intravascular effector lymphocyte entrapment but are not required for neutrophil entrapment or emigration inside endotoxin‐inflamed lungs. FASEB J. 30, 1767–1778 (2016). www.fasebj.org

Melanoma, a malignant neoplasm originating from melanocytes, stands as one of the most prevalent cancers globally, ranking fifth in terms of estimated new cases in recent years. Its aggressive nature and propensity for metastasis pose significant challenges in oncology. Recent advancements have led to a notable shift towards targeted therapies, driven by a deeper understanding of cutaneous tumor pathogenesis. Immunotherapy and tyrosine kinase inhibitors have emerged as promising strategies, demonstrating the potential to improve clinical outcomes across all disease stages, including neoadjuvant, adjuvant, and metastatic settings. Notably, there has been a groundbreaking development in the treatment of brain metastasis, historically associated with poor prognosis in oncology but showcasing impressive results in melanoma patients. This review article provides a comprehensive synthesis of the most recent knowledge on staging and prognostic factors while highlighting emerging therapeutic modalities, with a particular focus on neoadjuvant and adjuvant strategies, notably immunotherapy and targeted therapies, including the ongoing trials.

Left ventricular assist devices (LVADs) have been increasingly used in patients with advanced heart failure, either as a destination therapy or as a bridge to heart transplant. Continuous flow (CF) LVADs have revolutionized advanced heart failure treatment. However, significant vascular pathology and complications have been linked to their use. While the newer CF-LVAD generations have led to a reduction in some vascular complications such as stroke, no major improvement was noticed in the rate of other vascular complications such as gastrointestinal bleeding. This review attempts to provide a comprehensive summary of the effects of CF-LVAD on vasculature, including pathophysiology, clinical implications, and future directions.