Transnuclear mice reveal Peyer's patch iNKT cells that regulate B-cell class switching to IgG1

IFN-γ-dependent regulation of intestinal epithelial homeostasis by NKT cells

Intestinal homeostasis is maintained through the combined functions of epithelial and immune cells that collaborate to preserve the integrity of the intestinal barrier. However, the mechanisms by which immune cell populations regulate intestinal epithelial cell (IEC) homeostasis remain unclear. Here, we use a multi-omics approach to study the immune-epithelial crosstalk and identify CD1d-restricted natural killer T (NKT) cells as key regulators of IEC biology. We find that NKT cells are abundant in the proximal small intestine and show hallmarks of activation at steady state. Subsequently, NKT cells regulate the survival and the transcriptional and cellular composition landscapes of IECs in intestinal organoids, through interferon-γ (IFN-γ) and interleukin-4 secretion. In vivo, lack of NKT cells results in an increase in IEC turnover, while NKT cell activation leads to IFN-γ-dependent epithelial apoptosis. Our findings propose NKT cells as potent producers of cytokines that contribute to the regulation of IEC homeostasis.

Impact of chronic stress on intestinal mucosal immunity in colorectal cancer progression

Chronic stress is a significant risk factor that contributes to the progression of colorectal cancer (CRC) and has garnered considerable attention in recent research. It influences the distribution and function of immune cells within the intestinal mucosa through the "brain-gut" axis, altering cytokine and chemokine secretion and creating an immunosuppressive tumor microenvironment. The intestine, often called the "second brain," is particularly susceptible to the effects of chronic stress. Cytokines and chemokines in intestinal mucosal immunity（IMI） are closely linked to CRC cells' proliferation, metastasis, and drug resistance under chronic stress. Recently, antidepressants have emerged as potential therapeutic agents for CRC, possibly by modulating IMI to restore homeostasis and exert anti-tumor effects. This article reviews the role of chronic stress in promoting CRC progression via its impact on intestinal mucosal immunity, explores potential targets within the intestinal mucosa under chronic stress, and proposes new approaches for CRC treatment.

Loss of Mitochondrial Tusc2/Fus1 Triggers a Brain Pro-Inflammatory Microenvironment and Early Spatial Memory Impairment

Brain pathological changes impair cognition early in disease etiology. There is an urgent need to understand aging-linked mechanisms of early memory loss to develop therapeutic strategies and prevent the development of cognitive impairment. Tusc2 is a mitochondrial-resident protein regulating Ca2+ fluxes to and from mitochondria impacting overall health. We previously reported that Tusc2-/- female mice develop chronic inflammation and age prematurely, causing age- and sex-dependent spatial memory deficits at 5 months old. Therefore, we investigated Tusc2-dependent mechanisms of memory impairment in 4-month-old mice, comparing changes in resident and brain-infiltrating immune cells. Interestingly, Tusc2-/- female mice demonstrated a pro-inflammatory increase in astrocytes, expression of IFN-γ in CD4+ T cells and Granzyme-B in CD8+T cells. We also found fewer FOXP3+ T-regulatory cells and Ly49G+ NK and Ly49G+ NKT cells in female Tusc2-/- brains, suggesting a dampened anti-inflammatory response. Moreover, Tusc2-/- hippocampi exhibited Tusc2- and sex-specific protein changes associated with brain plasticity, including mTOR activation, and Calbindin and CamKII dysregulation affecting intracellular Ca2+ dynamics. Overall, the data suggest that dysregulation of Ca2+-dependent processes and a heightened pro-inflammatory brain microenvironment in Tusc2-/- mice could underlie cognitive impairment. Thus, strategies to modulate the mitochondrial Tusc2- and Ca2+- signaling pathways in the brain should be explored to improve cognitive health.

Invariant natural killer T cells balance B cell immunity

Invariant natural killer T (iNKT) cells mediate rapid immune responses which bridge the gap between innate and adaptive responses to pathogens while also providing key regulation to maintain immune homeostasis. Both types of important iNKT immune responses are mediated through interactions with innate and adaptive B cells. As such, iNKT cells sit at the decision-making fulcrum between regulating inflammatory or autoreactive B cells and supporting protective or regulatory B cell populations. iNKT cells interpret the signals in their environment to set the tone for subsequent adaptive responses, with outcomes ranging from getting licensed to maintain homeostasis as an iNKT regulatory cell (iNKT_reg ) or being activated to become an iNKT follicular helper (iNKT_FH ) cell supporting pathogen-specific effector B cells. Here we review iNKT and B cell cooperation across the spectrum of immune outcomes, including during allergy and autoimmune disease, tumor surveillance and immunotherapy, or pathogen defense and vaccine responses. Because of their key role as influencers, iNKT cells provide a valuable target for therapeutic interventions. Understanding the nature of the interactions between iNKT and B cells will enable the development of clinical interventions to strategically target regulatory iNKT and B cell populations or inflammatory ones, depending on the circumstance.

NKT cells and the regulation of intestinal immunity: a two‐way street

The mammalian gastrointestinal compartment is colonised by millions of microorganisms that have a central influence on human health. Intestinal homeostasis requires a continuous dialogue between the commensal bacteria and intestinal immune cells. While interactions between host and commensal bacteria are normally beneficial, allowing training and functional tuning of immune cells, dysregulated immune system-microbiota crosstalk can favour the development of chronic inflammatory diseases, as it is the case for inflammatory bowel disease (IBD). Natural killer T (NKT) cells, which recognise CD1-restricted microbial and self-lipids, contribute to the regulation of mucosal immunity by controlling intestinal homeostasis and participating in the development of IBD. Here, we provide an overview of the recently identified pathways underlying the crosstalk between commensal bacteria and NKT cells and discuss the effect of these interactions in intestinal health and disease.