The sentinel node technique is useful for studies of intestinal immunology in inflammatory bowel disease patients

The Role of the Lymphatic System in the Pathogenesis and Treatment of Inflammatory Bowel Disease

Although the number of therapeutic options for the treatment of inflammatory bowel disease (IBD) has increased in recent years, patients suffer from decreased quality of life due to non-response or loss of response to the currently available treatments. An increased understanding of the disease’s etiology could provide novel insights for treatment strategies in IBD. Lymphatic system components are generally linked to immune responses and presumably related to inflammatory diseases pathophysiology. This review aims to summarize findings on immune-mediated mechanisms in lymphoid tissues linked with IBD pathogenesis and (potential) novel treatments. Enhanced innate and adaptive immune responses were observed in mesenteric lymph nodes (MLNs) and other lymphoid structures, such as Peyer’s patches, in patients with IBD and in animal models. Furthermore, the phenomenon of lymphatic obstruction in the form of granulomas in MLNs and lymphatic vessels correlates with disease activity. There is also evidence that abnormalities in the lymphatic stromal components and lymph node microbiome are common in IBD and could be exploited therapeutically. Finally, novel agents targeting lymphocyte trafficking have been added to the treatment armamentarium in the field of IBD. Overall, gut-associated lymphoid tissue plays a key role in IBD immunopathogenesis, which could offer novel therapeutic targets.

Effect of cigarette smoke extract on the intestinal microenvironment of ulcerative colitis tissue

Background and Aim

Ulcerative colitis (UC) is an autoimmune disease characterized by inflammation in the gastrointestinal tract. The severity of UC is higher in nonsmokers than smokers; however, the biological mechanisms controlling this effect remain unknown. The aim of this study was to examine the effect of cigarette smoke extract (CSE) on inflamed and noninflamed colonic tissue from UC patients and to determine if inflammatory mediators, transcription factors, and T cell phenotypes are altered by CSE.

Methods

Blood and colonic biopsies were obtained from UC patients undergoing endoscopy. Biopsies were cultured in the presence or absence of CSE. Multiplex enzyme‐linked immunosorbent assay (ELISA) measured secreted levels of inflammatory mediators. Nuclear factor kappa‐light‐chain‐enhancer of activated B cells (NF‐κB) and Hypoxia‐inducible factor 1‐alpha (HIF‐1α) expression were measured by DNA‐binding ELISA. T cell phenotypes were assessed by flow cytometry in matched blood and biopsies.

Results

Secreted levels of interleukin 2 (IL‐2), interleukin 6 (IL‐6), tumor necrosis factor ‐ alpha (TNF‐α), chemokine (C‐C motif) ligand 2 (CCL2), and interleukin 10 (IL‐10) were significantly (all P < 0.05) decreased following treatment with CSE. This effect was specific to inflamed tissue and was not observed in noninflamed tissue. CSE did not alter the expression of NF‐κB or HIF‐1α. Assessment of T cell phenotypes in blood and tissue revealed that there were significantly more activated and exhausted T cells in the colonic tissue compared to matched blood. These profiles were not altered following CSE treatment.

Conclusion

These data suggest that observed effects of CSE in reducing inflammatory mediators ex vivo are specific to inflamed colonic tissue but are not due to the activation of NF‐κB or HIF‐1α and are not caused by alterations in subpopulations of T cells in these UC tissues.

Variation in Local and Systemic Pro-Inflammatory Immune Markers of Wild Wood Mice after Anthelmintic Treatment

The immune system represents a host's main defense against infection to parasites and pathogens. In the wild, a host's response to immune challenges can vary due to physiological condition, demography (age, sex), and coinfection by other parasites or pathogens. These sources of variation, which are intrinsic to natural populations, can significantly impact the strength and type of immune responses elicited after parasite exposure and infection. Importantly, but often neglected, a host's immune response can also vary within the individual, across tissues and between local and systemic scales. Consequently, how a host responds at each scale may impact its susceptibility to concurrent and subsequent infections. Here we analyzed how characteristics of hosts and their parasite infections drive variation in the pro-inflammatory immune response in wild wood mice (Apodemus sylvaticus) at both the local and systemic scale by experimentally manipulating within-host parasite communities through anthelmintic drug treatment. We measured concentrations of the pro-inflammatory cytokine tumor necrosis factor alpha (TNF-α) produced in vitro in response to a panel of toll-like receptor agonists at the local (mesenteric lymph nodes [MLNs]) and systemic (spleen) scales of individuals naturally infected with two gastrointestinal parasites, the nematode Heligmosomoides polygyrus and the protozoan Eimeria hungaryensis. Anthelmintic-treated mice had a 20-fold lower worm burden compared to control mice, as well as a four-fold higher intensity of the non-drug targeted parasite E. hungaryensis. Anthelmintic treatment differentially impacted levels of TNF-α expression in males and females at the systemic and local scales, with treated males producing higher, and treated females lower, levels of TNF-α, compared to control mice. Also, TNF-α was affected by host age, at the local scale, with MLN cells of young, treated mice producing higher levels of TNF-α than those of old, treated mice. Using complementary, but distinct, measures of inflammation measured across within-host scales allowed us to better assess the wood mouse immune response to changes in parasite infection dynamics after anthelmintic treatment. This same approach could be used to understand helminth infections and responses to parasite control measures in other systems in order to gain a broader view of how variation impacts the immune response.

Naïve T cells correlate with mucosal healing in patients with inflammatory bowel disease

BACKGROUND

In previous studies, adaptive immune responses involving T-helper cells have been shown to play an important role in inflammatory bowel diseases (IBDs).

METHODS

The aim of this study was to investigate any correlation between the degree of mucosal inflammation and the phenotype of gut-infiltrating T-helper cells. Biopsies from intestinal mucosa were obtained and intestinal T cells were analyzed with regard to activity and maturation markers. Patients with active colitis (39 with Crohn's disease and 47 with ulcerative colitis) were included and treated with corticosteroids, biologicals or leukocytapheresis. Flow cytometry was used to analyze activation marker expression on gut-infiltrating T-helper cells.

RESULTS

Mucosal healing was reflected by almost 100% increase of CD62L expression in mucosal T cells in patients in remission compared to those with active inflammation (p < 0.01). The frequency of mucosal-naïve CD4(+)CD45RA(+) T cells was reduced by 50% in mucosa displaying remission (5.3% compared to 12% of the total amount and CD4(+) T cells, p < 0.001). Surprisingly, the proportion of early activated T-helper cells (CD4(+)CD69(+)) did not differ between mucosa in remission and non-remission (43% and 42%, respectively). Moreover, no change in memory T-helper cells (CD4(+)CD45RO(+)) was observed (64% compared to 66%). The findings were independent of diagnosis (Crohn's disease or ulcerative colitis) or mode of treatment.

CONCLUSION

This study suggests that a reduced recruitment of naïve T-helper cells and increased frequency of T-helper cells with lymph node homing marker expression reflect mucosal healing in IBD. Surprisingly, the degree of activation of mucosal T-helper cells did not correlate with disease remission.

Evidence for immunosurveillance in intestinal premalignant lesions

The immunosurveillance theory argues that the immune system recognizes tumour-specific antigens expressed by transformed cells, which results in the destruction of cancer precursors before they become clinically manifest. As a model for the development of cancer, we set out to study premalignant lesions and immune responses in sentinel lymph nodes from patients with long-standing ulcerative colitis and progression of mucosal dysplasia. Mesenteric lymph nodes draining dysplastic and normal intestinal segments were identified by sentinel node technique during surgery in 13 patients with ulcerative colitis who were subjected to colectomy because of intestinal dysplasia. T cells were extracted from the lymph nodes and analysed by flow cytometry, and lymphocyte proliferation assays were set up in the presence of extracts from dysplastic and normal intestinal mucosa. Increase in CD4/CD8 ratio was observed in sentinel lymph nodes draining dysplastic epithelium compared to normal mucosa. The increase in CD4(+) T cells in relation to CD8(+) T cells correlated with the degree of dysplasia reflected by a significant increase in the ratio against low-grade dysplasia compared to indefinite dysplastic lesions. The T-cell response was specific to antigens from dysplastic epithelial lining as seen in proliferation assays. The observation suggests an important surveillance role for the immune system against premalignant intestinal lesions in patients with long-standing ulcerative colitis.