The intestinal immune system is crucial for protection from pathogenic infection and maintenance of mucosal homeostasis. We studied the intestinal immune microenvironment in a serovar Typhimurium intestinal infection mouse model. Intestinal lamina propria macrophages are the main effector cells in innate resistance to intracellular microbial pathogens. We found that Typhimurium infection augmented Tim-3 expression on intestinal lamina propria CD4 T cells and enhanced galectin-9 expression on F4/80 CD11b macrophages. Moreover, CD4 T cells promoted the activation and bactericidal activity of intestinal F4/80 CD11b macrophages via the Tim-3/galectin-9 interaction during Typhimurium infection. Blocking the Tim-3/galectin-9 interaction with α-lactose significantly attenuated the bactericidal activity of intracellular Typhimurium by macrophages. Furthermore, the Tim-3/galectin-9 interaction promoted the formation and activation of inflammasomes, which led to caspase-1 cleavage and interleukin 1β (IL-1β) secretion. The secretion of active IL-1β further improved bactericidal activity of macrophages and galectin-9 expression on macrophages. These results demonstrated the critical role of the cross talk between CD4 T cells and macrophages, particularly the Tim-3/galectin-9 interaction, in antimicrobial immunity and the control of intestinal pathogenic infections.

Persistent infection with the hepatitis B virus (HBV) can aggravate the state of immune tolerance, inhibit the function of immune cells, and even lead to immune cell exhaustion in the liver microenvironment. The dysfunction of immune cells causes HBV to escape immune surveillance and eradication. Increasing evidence has revealed the molecular and cellular mechanisms of the induction of T‐cell exhaustion during chronic viral persistence. However, the exact mechanisms of T cell exhaustion during chronic persistence of HBV infection are not fully understood. In this study, we analyzed the expression of inhibitory receptors and the exhausted status of liver T cells in a murine model with persistent HBV. We observed higher expression of the inhibitory receptors PD‐1, LAG‐3, and CD160 on liver CD8+ T cells accompanied by lower production of IFN‐γ and TNF‐α in HBV persistence mice. T cell‐specific deficiency of the transcription factor Eomes significantly decreased the expression of the inhibitory receptors, restored the cytokine production of hepatic CD8+ T cells, and promoted HBV clearance. Similar phenomena were observed in peripheral blood CD8+ T cells from CHB patients. Mechanistically, Eomes not only directly promoted CD160 expression but also indirectly facilitated the coexpression of inhibitory receptors (PD‐1, LAG‐3, CD160) and T cell exhaustion by enhancing the transcription capacity of other key transcription factors (NFATc1, Blimp1, and FoxO1). These findings provide insight into the transcriptional regulation mechanisms of T cell exhaustion during chronic persistence of HBV and suggest novel therapeutic targets to reverse T cell exhaustion and eradicate HBV persistence.

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