Colorectal cancer (CRC) is the third most prevalent cancer and understanding its tumor microenvironment (TME) is crucial for the development of innovative therapies. Despite the presence of B cells in CRC infiltrate, their clinical significance is poorly understood. In this study, we observed an enrichment of double-negative (DN) B cells, a subset lacking surface IgD and CD27, in CRC biopsies. Typically underrepresented in physiological conditions, DN B cells expand in certain chronic infections, autoimmune diseases, and cancers. Within this subpopulation, low CD21 expression-a phenotypic hallmark of exhaustion-was observed. Consistently, DN B cells displayed low metabolic activity. Accordingly, total B cells infiltrating CRC tissues showed a diminished capacity to differentiate into antibody-secreting cells (ASCs) upon stimulation. In the murine setting, CRC organoids decreased the frequency of ASCs in co-cultured B cells and induced metabolic dysfunction, marked by altered glucose and fatty acid uptake and dysregulated expression of key metabolic proteins. Moreover, B cells displayed reduced glycolysis and mitochondrial respiration, despite increased mitochondrial dependence. This study provides evidence for DN B cell accumulation within CRC infiltrate and metabolic reprogramming of B cells, suggesting that targeting B cell metabolism may represent a promising strategy to potentiate anti-tumor immune responses.

IntroductionIn colorectal cancer (CRC), mast cells (MCs) modulate tumor and immune cell interactions, influencing patient prognosis, though their role remains not fully elucidated. Our group previously uncovered that in the intestine MCs provide support for the effector functions of B cells, both in physiology and inflammation.MethodsIn this work we investigated the relationship between the activation of MCs in CRC and recruitment and accumulation of B cells in the tumor environment.ResultsWe observed infiltration of both B cells and MCs in the tumor tissue and uncovered accumulation of CCR6+ B cells in tumor lymph nodes (LNs), both in the mouse model and in human patients. Enhanced expression of the CCL20 chemokine, the ligand of CCR6, was observed in cancer tissue compared to the normal condition, along with an increased CCL20 gradient in mouse tumor-draining LNs. We proved that TNF-α released by activated-MCs was required to sustain CCL20 production from cancer cells in vitro.DiscussionThe accumulation of CCR6+ B cells in CRC context may then rely on the crosstalk between MCs and CRC cells. Our findings suggest that B cell immunosurveillance may be indirectly promoted through the clinical modulation of TNF-α secretion at the early stages of colorectal tumorigenesis.

IntroductionL-Tryptophan (Trp) metabolism is impaired across various chronic inflammatory pathologies, including Multiple Sclerosis (MS). Trp processing relies on three metabolic routes, namely Kynurenine, Serotonin and Indole pathways. The host microbiota significantly impacts Trp metabolism, primarily by being responsible for Indole metabolites production and secondarily by shaping both Kynurenine and Serotonin pathways. Pathological conditions and pharmaceutical treatments can elicit changes in microbial populations, leading to alterations in metabolites production and therefore determining rearrangements in host metabolism. Currently, no simultaneous exploration and comparison of all three Trp related metabolic routes has been performed in the context of MS patients before and after Ocrelizumab (OCR) treatment.MethodsBy performing mass spectrometry on plasma samples collected from healthy controls and MS patients before and six months after OCR treatment we provided a comparative investigation of Trp metabolomics profile.Results and discussionOur data points out to concurrent alterations of Trp-related pathways among both OCR treated and untreated MS patients. Furthermore, MS treated patients presented a pattern resembling health state for various metabolites across the pathways. The results reported in our research may contribute to unveiling new perspectives and understanding regarding MS pathogenetic mechanisms.

B cells have crucial roles in the initiation and progression of many pathological conditions, and several therapeutic strategies have targeted the function of these cells. The advent of immunometabolism has provided compelling evidence that the metabolic reprogramming of immune cells can dramatically alter physiopathological immune activities. A better knowledge of the metabolic profiles of B cells can provide valuable means for developing therapies tuning defined cell pathways. Here we review the cellular and molecular mechanisms by which immunometabolism controls the physiology and pathophysiology of B cells and discuss the experimental evidence linking B cell metabolism to health, autoimmunity, and cancer. Considering that several metabolic pathways in B cells are involved differently, or even in opposite ways, in health and disease, we discuss how targeted modulation of B cell immunometabolism could be exploited mechanistically to rebalance abnormal B cell functions that have become altered in disease states.

It is common knowledge that mast cells (MCs) exert different roles in the gastrointestinal tract, from the maintenance of homeostasis to the onset and propagation of different gut diseases such as food allergies, infections, inflammation, and cancer. However, the mechanisms through which MCs dialog and influence the intestinal tissue are not completely known. To get insight into the bidirectional crosstalk between MCs and the intestinal microenvironment, both in homeostatic and pathological settings, colon organoids from intestinal epithelium of healthy mice and adenomas from AOM/DSS-treated mice have been exploited and co-cultured with MCs. The influence of MCs on organoid architecture and the effect of healthy and tumoral organoids on the phenotype and responsiveness of MCs have been addressed. We observed that MCs interact with intestinal organoids and contribute to the differentiation of healthy organoids by upregulating the expression of mucin-2, chromogranin A, cadherin-1, and claudin 4. On the contrary, in co-culture with tumoral organoids a decrease in cell proliferation, chromogranin A, and lysozyme expression was observed. Tumoral organoids have been shown to activate MCs via the IL-33/ST2 axis leading to increased release of TNF-α which in turn was responsible for the observed effects on tumoral organoids. Our results indicate that MCs are important mediators of intestinal tissue homeostasis and that a different environment can shape and direct MCs toward the dampening or propagation of the inflammatory response. Ultimately, our MC-organoid co-cultures represent a valid in vitro tool to investigate the role of MCs in the gut.

Colorectal cancer represents 10% of all new cancer cases each year and accounts for almost 10% of all cancer deaths. According to the WHO, by 2040 there will be a 60% increase in colorectal cancer cases. These data highlight the need to explore new therapeutic strategies. Classical interventions include surgical resection, chemotherapy and radiotherapy, which are invasive strategies that have many side effects on the patients and greatly affect their quality of life. A great advance in the treatment of this cancer type, as well as of all the others, could be the development of a vaccination strategy preventing the onset, the progression or the relapse of the pathology. In this review, we summarize the main vaccination strategies that are being studied for the treatment of colorectal cancer (CRC) and finally explore the possibility of using B-cells for the development of a new type of vaccine.

IL-10 is the best known and most studied anti-inflammatory cytokine and, in the last 20 years, it has acquired even greater fame as it has been associated with the regulatory phenotype of B cells. Indeed, although great efforts have been made to find a unique marker, to date IL-10 remains the main way to follow both murine and human regulatory B cells, hence the need of precise and reproducible methods to identify and purify IL-10-producing B cells for both functional and molecular downstream assays. In this chapter, we present our protocols to isolate these cells from the murine spleen and peritoneum and from human peripheral blood. Since the production of IL-10 by B cells is not only a weapon to counteract the adverse effect of pro-inflammatory cytokines but also a response to cellular activation, we focused on those B cells that are prone to IL-10 production and detectable following a short-term stimulation with phorbol-12-myristate-13-acetate, ionomycin, and lipopolysaccharide (murine system) or CpG (human system).

Epigenetic studies are becoming increasingly common in the immunology field thanks to the support of cutting edge technology and to their potential of providing a large amount of data at the single cell level. Moreover, epigenetic modifications were shown to play a role in autoimmune/inflammatory disorders, paving the way for the possibility of using the results of epigenetic studies for therapeutic purposes. In recent years, epigenetic marks such as DNA methylation, histone modifications and nucleosome positioning were shown to regulate B cell fate and function during an immune response, but very little has been done in the context of one of the most recently discovered B cell subsets, that is regulatory B cells. Although no consensus has yet been found on the identity of these immunosuppressive B cells, the role of the IL-10 cytokine is consolidated, both in the murine and human setting. In this chapter we will focus on the analysis of the methylation profile of a gene of interest and we will specifically describe cloning and pyrosequencing bisulphite sequencing PCR (BSP). Given the specific context, we will provide tips and tricks for the analysis of the il-10 gene locus. Nonetheless, the methods presented are valid for the study of any gene of interest.