Age-dependent rise in IFN-γ competence undermines effective type 2 responses to nematode infection

Divergent immediate and delayed effects of juvenile exposure to doxorubicin on the thymus in C57BL/6 mice

The long-term effects of doxorubicin (DOX) chemotherapy on thymic immune function in childhood cancer survivors remain inadequately understood. This study explores the immediate and delayed impacts of low-dose DOX on thymic immune populations using a juvenile mouse model. Male mice received intraperitoneal DOX injections (4 mg/kg/week) for three weeks, with evaluations performed at one- and five-weeks post treatment. Thymic samples were collected and analyzed using multi-parameter flow cytometry to assess changes in immune cell composition and phenotype. Additionally, real-time polymerase chain reaction (RT-PCR) was employed to measure gene expression of cytokines and senescence markers. One week after DOX administration, significant thymic atrophy was evident. While mature CD3+CD4+ T-cell frequency remained unchanged, CD3+CD8+ T-cells significantly increased, suggesting differential effects on T-cell subsets. PD1+ expression increased across naïve and memory CD4+ T-cell subsets, suggesting activation or exhaustion. Additionally, Ki67+ expression was elevated in naïve and memory CD8+ T-cells, indicating enhanced proliferation. Gene expression analysis revealed upregulation of Foxn1, Pax1, Ifnγ, and Il7 whereas Il6 and Il17 were downregulated. Furthermore, Cdkn1a (p21) expression was elevated, suggesting immune dysregulation and early immunosenescence. At five weeks, thymic weight rebounded; however, T-cell subsets displayed persistent perturbations. Central memory and effector memory CD4+ T-cells were reduced, while naïve CD4+ T-cells showed increased Ki67+ expression. In contrast, CD8+ T-cells subsets remained largely unchanged, except for a decrease in central memory cells. Although expression of thymus-related genes was normalized, p21 expression remained elevated, suggesting lingering immunosenescence. These findings highlight the complex effects of DOX, including acute thymic atrophy due to T-cell depletion, and a delayed recovery with persistent immunosenescence, underscoring the need for strategies to preserve immune function in childhood cancer survivors.

A type 1 immune-stromal cell network mediates disease tolerance against intestinal infection

Type 1 immunity mediates host defense through pathogen elimination, but whether this pathway also impacts tissue function is unknown. Here, we demonstrate that rapid induction of interferon γ (IFNγ) signaling coordinates a multicellular response that is critical to limit tissue damage and maintain gut motility following infection of mice with a tissue-invasive helminth. IFNγ production is initiated by antigen-independent activation of lamina propria CD8+ T cells following MyD88-dependent recognition of the microbiota during helminth-induced barrier invasion. IFNγ acted directly on intestinal stromal cells to recruit neutrophils that limited parasite-induced tissue injury. IFNγ sensing also limited the expansion of smooth muscle actin-expressing cells to prevent pathological gut dysmotility. Importantly, this tissue-protective response did not impact parasite burden, indicating that IFNγ supports a disease tolerance defense strategy. Our results have important implications for managing the pathophysiological sequelae of post-infectious gut dysfunction and chronic inflammatory diseases associated with stromal remodeling.

Musimbi Z, Mugo RM, Midha A, Hartmann S, Rausch S. Liver-draining portal lymph node responds to enteric nematode infection by generating highly parasite-specific follicular T helper and B cell responses

Introduction

While research on the gut-liver axis in non-communicable liver diseases has expanded exponentially, few studies have investigated the liver-gut relationship in the context of gastrointestinal nematode infections. This study aimed to determine whether liver-draining lymph nodes (LLNs) contribute to the immune response against a strictly enteric nematode infection.

Methods

We analyzed the cellular and functional immune responses in the portal (PLN) and celiac (CLN) liver-draining lymph nodes following infection with the small intestinal nematode Heligmosomoides (polygyrus) bakeri (H. bakeri). The composition of dendritic cells and CD4+ T cell subsets in LLNs was compared to the mesenteric lymph nodes (MLN), the primary draining site of gut infections. Additionally, we examined Th2 effector cell expansion, plasmablast generation, and B cell activation across these lymphoid sites.

Results

Both PLN and CLN exhibited increased cellularity at d14 post-infection. The immune profile in CLN closely resembled that of MLN, characterized by a robust expansion of GATA-3+ Th2 effector cells at days 6 and 14 post-infection. This was accompanied by an early plasmablast response, producing low-affinity IgG1 antibodies targeting immune-dominant excretory-secretory (ES) products. In contrast, PLN showed weaker Th2 responses and lower early plasma cell responses compared to MLN and CLN. However, PLN displayed strong follicular T helper (TFH) activity, with a B cell profile biased toward germinal center reactions. This led to high-affinity IgG1 antibodies specifically binding VAL-1 and ACE-1.

Discussion

These findings demonstrate, for the first time, that liver-draining lymph nodes actively participate in the adaptive immune response to enteric nematode infections. While MLN and CLN function synergistically in generating early Th2 effector cells and rapid extrafollicular IgG1+ plasma cell responses, PLN specializes in TFH-driven germinal center reactions and affinity maturation.

Differential resistance to nematode infection is associated with the genotype- and age-dependent pace of intestinal T cell homing

The resistance of inbred mice to nematode infections varies depending on the extent of protective Th2 responses. Here, we compared two mouse lines differing in resistance to infection with the enteric nematode Heligmosomoides polygyrus bakeri despite the similar instruction of GATA-3+ T effector cells. Resistant BALB/c mice rapidly recruited high numbers of Th2 cells to the gut within the 1-week time frame required for larval development in the intestinal submucosa. C57BL/6 mice failed in the optimal control of early nematode fitness, with mucosal Th2 response peaking after 2 weeks when the larvae had left the tissue and relocated to the gut lumen as adult worms. The faster homing of Th2 cells to the gut of BALB/c mice is related to the extensive expression of the chemokine receptor CCR9 in GATA-3+ cells and higher frequencies of aldehyde dehydrogenase expressing dendritic cells present in mesenteric lymph nodes. Furthermore, nematode-infected older BALB/c mice displayed impaired resistance due to delayed mucosal homing of effector cells, which synergized with more numerous Th2/1 hybrid cells acting as IFN-γ-dependent confounders of type 2 responses. Hence, the distinct kinetics of effector cell recruitment to the infected gut and the quality of GATA-3+ T cell responses contribute to the genotype- and age-dependent resistance to intestinal nematode infections.

Ascaris suum infection in juvenile pigs elicits a local Th2 response in a setting of ongoing Th1 expansion

Ascaris spp. undergo extensive migration within the body before establishing patent infections in the small intestinal tract of humans and pigs. However, whether larval migration is critical for inducing efficient type 2 responses remains poorly understood. Therefore, we investigated systemic versus local adaptive immune responses along the hepato-tracheal migration of Ascaris suum during primary, single infections in conventionally raised pigs. Neither the initial invasion of gut tissue nor migration through the liver resulted in discernable Th2 cell responses. In contrast, lung-stage larvae elicited a Th2-biased pulmonary response, which declined after the larvae had left the lungs. In the small intestine, we observed an accumulation of Th2 cells upon the arrival of fourth-stage larvae (L4) to the small intestinal lumen. In parallel, we noticed robust and increasing Th1 responses in circulation, migration-affected organs, and draining lymph nodes. Phenotypic analysis of CD4+ T cells specifically recognizing A. suum antigens in the circulation and lung tissue of infected pigs confirmed that the majority of Ascaris-specific T cells produced IL-4 (Th2) and, to a much lesser extent, IL-4/IFN-g (Th2/1 hybrids) or IFN-g alone (Th1). These data demonstrate that lung-stage but not the early liver-stage larvae lead to a locally restricted Th2 response. Significant Th2 cell accumulation in the small intestine occurs only when L4 complete the body migration. In addition, Th2 immunity seems to be hampered by the concurrent, nonspecific Th1 bias in growing pigs. Together, the late onset of Th2 immunity at the site of infection and the Th1-biased systemic immunity likely enable the establishment of intestinal infections by sufficiently large L4 stages and pre-adult worms, some of which resist expulsion mechanisms.

Helminth Infection-Induced Increase in Virtual Memory CD8 T Cells Is Transient, Driven by IL-15, and Absent in Aged Mice

CD8 virtual memory T (TVM) cells are Ag-naive CD8 T cells that have undergone partial differentiation in response to common γ-chain cytokines, particularly IL-15 and IL-4. TVM cells from young individuals are highly proliferative in response to TCR and cytokine stimulation but, with age, they lose TCR-mediated proliferative capacity and exhibit hallmarks of senescence. Helminth infection can drive an increase in TVM cells, which is associated with improved pathogen clearance during subsequent infectious challenge in young mice. Given the cytokine-dependent profile of TVM cells and their age-associated dysfunction, we traced proliferative and functional changes in TVM cells, compared with true naive CD8 T cells, after helminth infection of young and aged C57BL/6 mice. We show that IL-15 is essential for the helminth-induced increase in TVM cells, which is driven only by proliferation of existing TVM cells, with negligible contribution from true naive cell differentiation. Additionally, TVM cells showed the greatest proliferation in response to helminth infection and IL-15 compared with other CD8 T cells. Furthermore, TVM cells from aged mice did not undergo expansion after helminth infection due to both TVM cell-intrinsic and -extrinsic changes associated with aging.