Characterization of B cell immunometabolism in colorectal cancer using murine organoids as models of disease

B lymphocytes are important components of adaptive immune responses. Following antigen recognition, naïve B cells undergo a rapid expansion and differentiate into plasma cells that secrete a large repertoire of antibodies and pro-inflammatory cytokines. In recent years, a growing body of evidence has shown that the significant metabolic changes resulting from immune activation, in addition to sustain the rapid increase in biomass and proliferation, profoundly affect the immune cell functions. To date, the molecular mechanisms underlying the metabolic programs adopted by B cells upon activation and enabling effective immune responses are yet to be defined. Even less is known about how different factors other than the activation state, including the anatomical site, cellular interactions and nutrient and oxygen availability, influence their metabolism and consequently, their function. Pathological conditions can further influence the metabolism and functions of immune cells, which makes it necessary to study these aspects in a context-specific manner. Therefore, the first part of this study aimed at investigating in the murine setting the molecular mechanisms underlying B cell metabolic changes upon T cell dependent and independent stimulations, with the purpose of finding metabolic targets to enhance or inhibit their activation in pathological contexts where it is respectively impaired or excessive. This study revealed a more robust and immediate activation of B cells in response to the T cell independent stimulus, the lipopolysaccharide (LPS), compared to that induced via CD40 by using the anti-CD40 monoclonal antibody (anti-CD40 mAb). Despite the differences in timing, the metabolic adaptations that occur upon T cell dependent and independent stimulations were mediated by the same molecular mechanisms including the increase in glucose import, protein expression levels of glycolytic and TCA enzymes, mitochondrial membrane potential and mitochondrial mass. In the second part of this thesis, B cell metabolism and function were investigated in the intestinal context, under physiological conditions and in colorectal cancer (CRC), to assess the influence of these specific environments on B cell behavior. Mouse intestinal organoids were used as models of healthy and cancerous intestine. B cells co-cultured with tumor organoids showed a reduced proliferation which was reflected by a decreased glycolytic function and mitochondrial respiration. These metabolic features were accompanied by an inhibited differentiation toward their fully mature counterparts along with an augmented expression of chemokines involved in the recruitment of other immune cell types. A further investigation of intestinal B cell metabolism and function would hopefully allow, in a future, the identification of metabolic pathways that can be targeted to enhance specific immune responses against this type of cancer.