Tumours maximize their chance of metastasizing by evoking a systemic inflammatory cascade in mouse models of spontaneous breast cancer metastasis. That tumorigenesis can be closely linked to an inflammatory microenvironment has been well established. In a new study, Karin de Visser and colleagues estimate the more systemic inflammatory effects observed in a mouse model of breast cancer. They find that interleukin (IL)-1β expression in tumours elicits IL-17 expression in γδ T cells at a local level, which through granulocyte colony-stimulating factor production promotes systemic accumulation of neutrophils in multiple organs. Interfering with this cascade of events, for example at the level of neutrophil activation, reduces lung and lymph node metastases in this breast cancer model. These findings illustrate the perhaps wider than anticipated systemic effects elicited by localized tumours, at the same time offering multiple points of potential therapeutic interference. Metastatic disease remains the primary cause of death for patients with breast cancer. The different steps of the metastatic cascade rely on reciprocal interactions between cancer cells and their microenvironment. Within this local microenvironment and in distant organs, immune cells and their mediators are known to facilitate metastasis formation1,2. However, the precise contribution of tumour-induced systemic inflammation to metastasis and the mechanisms regulating systemic inflammation are poorly understood. Here we show that tumours maximize their chance of metastasizing by evoking a systemic inflammatory cascade in mouse models of spontaneous breast cancer metastasis. We mechanistically demonstrate that interleukin (IL)-1β elicits IL-17 expression from gamma delta (γδ) T cells, resulting in systemic, granulocyte colony-stimulating factor (G-CSF)-dependent expansion and polarization of neutrophils in mice bearing mammary tumours. Tumour-induced neutrophils acquire the ability to suppress cytotoxic T lymphocytes carrying the CD8 antigen, which limit the establishment of metastases. Neutralization of IL-17 or G-CSF and absence of γδ T cells prevents neutrophil accumulation and downregulates the T-cell-suppressive phenotype of neutrophils. Moreover, the absence of γδ T cells or neutrophils profoundly reduces pulmonary and lymph node metastases without influencing primary tumour progression. Our data indicate that targeting this novel cancer-cell-initiated domino effect within the immune system—the γδ T cell/IL-17/neutrophil axis—represents a new strategy to inhibit metastatic disease.

Patients with primary solid malignancies frequently exhibit signs of systemic inflammation. Notably, elevated levels of neutrophils and their associated soluble mediators are regularly observed in cancer patients, and correlate with reduced survival and increased metastasis formation. Recently, we demonstrated a mechanistic link between mammary tumor-induced IL17-producing γδ T cells, systemic expansion of immunosuppressive neutrophils and metastasis formation in a genetically engineered mouse model for invasive breast cancer. How tumors orchestrate this systemic inflammatory cascade to facilitate dissemination remains unclear. Here we show that activation of this cascade relies on CCL2-mediated induction of IL1β in tumor-associated macrophages. In line with these findings, expression of CCL2 positively correlates with IL1Β and macrophage markers in human breast tumors. We demonstrate that blockade of CCL2 in mammary tumor-bearing mice results in reduced IL17 production by γδ T cells, decreased neutrophil expansion and enhanced CD8⁺ T cell activity. These results highlight a new role for CCL2 in facilitating the breast cancer-induced pro-metastatic systemic inflammatory γδ T cell – IL17 – neutrophil axis.

After the resolution of the acute phase of infection, otherwise quiescent antigen-experienced CD8 ⁺ T cells confer rapid protection upon reinfection with viral pathogens or, in the case of persistent viruses, help to maintain control of the infection. Depending on the type of virus, antigen-specific CD8 ⁺ T cells have distinct traits, ranging from typical memory cell properties in the case of rapidly cleared viruses to immediate effector functions for persistent viruses. We here show that both the differentiation stage, defined by the expression of cell surface markers, such as CD45RA, CCR7, CD28, and CD27, and distinct expression levels of T-bet and eomesodermin (Eomes) predict the functional profile of antigen-experienced CD8 ⁺ T cells. Furthermore, virus-specific CD8 ⁺ T cells targeting different respiratory syncytial virus-, influenza A virus-, Epstein-Barr virus (EBV)-, human cytomegalovirus (hCMV)-, and HIV-1-specific epitopes adopt distinct T-bet and Eomes expression patterns that appear to be installed early during the primary response. Importantly, the associations between surface phenotype, T-bet/Eomes expression levels, and the expression of markers that predict CD8 ⁺ T-cell function change according to viral infection history, particularly against the background of HIV-1 and, to lesser extent, of human cytomegalovirus and/or Epstein-Barr virus infection. Thus, the functionality of human antigen-experienced CD8 ⁺ T cells follows at least two dimensions, one outlined by the surface phenotype and another by the T-bet/Eomes expression levels, which are determined by previous or persistent viral challenges. IMPORTANCE Functional human CD8 ⁺ T-cell subsets have been defined using surface markers like CD45RA, CCR7, CD28, and CD27. However, the induction of function-defining traits, like granzyme B expression, is controlled by transcription factors like T-bet and Eomes. Here, we describe how T-bet and Eomes levels distinctly relate to the expression of molecules predictive for CD8 ⁺ T-cell function in a surface phenotype-independent manner. Importantly, we found that central memory and effector memory CD8 ⁺ T-cell subsets differentially express T-bet, Eomes, and molecules predictive for function according to viral infection history, particularly so in the context of HIV-1 infection and, to lesser extent, of latent EBV- and/or hCMV-infected, otherwise healthy adults. Finally, we show that the distinct phenotypes and T-bet/Eomes levels of different virus-specific CD8 ⁺ T-cell populations are imprinted early during the acute phase of primary infection in vivo . These findings broaden our understanding of CD8 ⁺ T-cell differentiation.

Differentiation of B cells into antibody-secreting cells (ASCs) is a key process to generate protective humoral immunity. A detailed understanding of the cues controlling ASC differentiation is important to devise strategies to modulate antibody formation. Here, we dissected differentiation trajectories of human naive B cells into ASCs using single-cell RNA sequencing. By comparing transcriptomes of B cells at different stages of differentiation from an in vitro model with ex vivo B cells and ASCs, we uncovered a novel pre-ASC population present ex vivo in lymphoid tissues. For the first time, a germinal-center-like population is identified in vitro from human naive B cells and possibly progresses into a memory B cell population through an alternative route of differentiation, thus recapitulating in vivo human GC reactions. Our work allows further detailed characterization of human B cell differentiation into ASCs or memory B cells in both healthy and diseased conditions.

Objectives To evaluate whether a third vaccination shows an added effect on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) T-cell responses in patients with multiple sclerosis treated with ocrelizumab or fingolimod. Methods This is a substudy of a prospective multicenter study on SARS-CoV-2 vaccination in patients with immune-mediated diseases. Patients with MS treated with ocrelizumab, fingolimod, and no disease-modifying therapies and healthy controls were included. The number of interferon (IFN)-γ secreting SARS-CoV-2–specific T cells at multiple time points before and after 3 SARS-CoV-2 vaccinations were evaluated. Results In ocrelizumab-treated patients (N = 24), IFN-γ–producing SARS-CoV-2–specific T-cell responses were induced after 2 vaccinations with median levels comparable to healthy controls (N = 12) and patients with MS without disease-modifying therapies (N = 10). A third vaccination in ocrelizumab-treated patients (N = 8) boosted T-cell responses that had declined after the second vaccination, but did not lead to higher overall T-cell responses as compared to immediately after a second vaccination. In fingolimod-treated patients, no SARS-CoV-2–specific T cells were detected after second (N = 12) and third (N = 9) vaccinations. Discussion In ocrelizumab-treated patients with MS, a third SARS-CoV-2 vaccination had no additive effect on the maximal T-cell response but did induce a boost response. In fingolimod-treated patients, no T-cell responses could be detected following both a second and third SARS-CoV-2 vaccination.

High-affinity antibody-secreting cells (ASC) arise from terminal differentiation of B-cells after coordinated interactions with T follicular helper (Tfh) cells in germinal centers (GC). Elucidation of cues promoting human naive B-cells to progress into ASCs is challenging, as this process is notoriously difficult to induce in vitro while maintaining enough cell numbers to investigate the differentiation route(s). Here, we describe a minimalistic in vitro culture system that supports efficient differentiation of human naive B-cells into antibody-secreting cells. Upon initial stimulations, the interplay between level of CD40 costimulation and the Tfh cell-associated cytokines IL-21 and IL-4 determined the magnitude of B-cell expansion, immunoglobulin class-switching and expression of ASC regulator PRDM1. In contrast, the B-cell-specific transcriptional program was maintained, and efficient ASC formation was hampered. Renewed CD40 costimulation and Tfh cytokines exposure induced rapid secondary STAT3 signaling and extensive ASC differentiation, accompanied by repression of B-cell identity factors PAX5, BACH2 and IRF8 and further induction of PRDM1. Our work shows that, like in vivo, renewed CD40L costimulation also induces efficient terminal ASC differentiation after initial B-cell expansion in vitro. This culture system for efficient differentiation of human naive B-cells into ASCs, while also maintaining high cell numbers, may form an important tool in dissecting human naive B-cell differentiation, thereby enabling identification of novel transcriptional regulators and biomarkers for desired and detrimental antibody formation in humans.