Limited role of the spleen in a mouse model of trained immunity: Impact on neutrophilia

Allergenicity assessment of β-lactoglobulin ferulic acid-glucose conjugates

We prepared the β-lactoglobulin (BLG)-ferulic acid (FA)-glucose (Glu) conjugates by alkaline method and Maillard reaction to assess the allergenicity. FA and Glu can form a ternary covalent conjugate with BLG, as evidenced by the shortening of SEC retention time, upward migration of SDS-PAGE protein bands, considerable decrease in free amino and sulfhydryl content, and changes in multistructure. BLG-Glu-FA conjugates weakly bound to immunoglobulin E in allergic sera was weak, reduced interleukin 4 and tumor necrosis factor α levels in RBL-2H3 cells and histamin and interleukin 6 secretion levels in KU812 cells, and inhibited the nuclear factor-κB signaling pathway. In vivo experiments showed that the conjugates regulated T-cell homeostasis in mouse splenic and mesenteric lymphocytes and attenuated splenic and duodenal immune injury. Therefore, the conjugates of BLG with FA combined with Glu altered the epitope structure and exhibited low allergenicity.

Dietary Intake of Yeast-Derived β-Glucan and Rice-Derived Arabinoxylan Induces Dose-Dependent Innate Immune Priming in Mice

Beta-glucans and arabinoxylans are known for their immunostimulatory properties. However, in vivo these have been documented almost exclusively following parenteral administration, underemphasizing oral intake. C57BL/6 mice are fed either a control diet or a diet supplemented with yeast-derived whole β-glucan particle (yWGP) or with rice-derived arabinoxylan (rice bran-1) at a concentration of 1%, 2.5%, or 5% weight/weight (w/w) for 2 weeks. Thereafter, cells from blood, bone marrow, and spleen are collected for ex vivo stimulation with various microbial stimuli. Dietary intake of yWGP for 2 weeks at concentrations of 1% and 2.5% w/w increases ex vivo cytokine production in mouse blood and bone marrow, whereas 5% w/w yWGP shows no effect. In the spleen, cytokine production remains unaffected by yWGP. At a concentration of 1% w/w, rice bran-1 increases ex vivo cytokine production by whole blood, but 2.5% and 5% w/w cause inhibitory effects in bone marrow and spleen. This study demonstrates that dietary yWGP and rice bran-1 induce immune priming in mouse blood and bone marrow, with the strongest effects observed at 1% w/w. Future human trials should substantiate the efficacy of dietary β-glucans and arabinoxylans to bolster host immunity, focusing on dose optimization.

The causes and consequences of trained immunity in myeloid cells

Conventionally, immunity in humans has been classified as innate and adaptive, with the concept that only the latter type has an immunological memory/recall response against specific antigens or pathogens. Recently, a new concept of trained immunity (a.k.a. innate memory response) has emerged. According to this concept, innate immune cells can exhibit enhanced responsiveness to subsequent challenges, after initial stimulation with antigen/pathogen. Thus, trained immunity enables the innate immune cells to respond robustly and non-specifically through exposure or re-exposure to antigens/infections or vaccines, providing enhanced resistance to unrelated pathogens or reduced infection severity. For example, individuals vaccinated with BCG to protect against tuberculosis were also protected from malaria and SARS-CoV-2 infections. Epigenetic modifications such as histone acetylation and metabolic reprogramming (e.g. shift towards glycolysis) and their inter-linked regulations are the key factors underpinning the immune activation of trained cells. The integrated metabolic and epigenetic rewiring generates sufficient metabolic intermediates, which is crucial to meet the energy demand required to produce proinflammatory and antimicrobial responses by the trained cells. These factors also determine the efficacy and durability of trained immunity. Importantly, the signaling pathways and regulatory molecules of trained immunity can be harnessed as potential targets for developing novel intervention strategies, such as better vaccines and immunotherapies against infectious (e.g., sepsis) and non-infectious (e.g., cancer) diseases. However, aberrant inflammation caused by inappropriate onset of trained immunity can lead to severe autoimmune pathological consequences, (e.g., systemic sclerosis and granulomatosis). In this review, we provide an overview of conventional innate and adaptive immunity and summarize various mechanistic factors associated with the onset and regulation of trained immunity, focusing on immunologic, metabolic, and epigenetic changes in myeloid cells. This review underscores the transformative potential of trained immunity in immunology, paving the way for developing novel therapeutic strategies for various infectious and non-infectious diseases that leverage innate immune memory.