Study and isolation of human intestinal dendritic cell and macrophage subsets

Dendritic cells and macrophages are the main antigen-presenting cells (APC). In the gut, they control the mechanisms of tolerance toward commensals and nutrients, at the time that they maintain their capacity to trigger immune responses against invading pathogens. Nevertheless, this balance is not perfect as it can get disrupted like in inflammatory bowel disease (where they drive an abnormal immune response against the microbiota) or in coeliac disease (where they trigger an immune response against dietary gluten). Therefore, the study of human intestinal APC subsets is crucial not just to get a deeper insight in the mechanisms of human intestinal homeostasis, but also to understand the pathogenesis of inflammatory bowel disease and coeliac disease. Nevertheless, their study is quite complicated as despite their relevance, their numbers are scare in the intestinal mucosa. Therefore, we hereby describe different approaches to study human intestinal dendritic cell and macrophage subsets in the human intestinal mucosa.

Effect of the live oral attenuated typhoid vaccine, Ty21a, on systemic and terminal ileum mucosal CD4+ T memory responses in humans

Our current understanding of CD4+ T-cell-mediated immunity (CMI) elicited by the oral live attenuated typhoid vaccine Ty21a is primarily derived from studies using peripheral blood. Very limited data are available in humans regarding mucosal immunity (especially CD4+ T) at the site of infection (e.g. terminal ileum; TI). Here using multiparametric flow cytometry, we examined the effect of Ty21a immunization on TI-lamina propria mononuclear cells (LPMC) and peripheral blood CD4+ T memory (TM) subsets in volunteers undergoing routine colonoscopy. Interestingly, we observed significant increases in the frequencies of LPMC CD4+ T cells following Ty21a immunization, restricted to the T effector/memory (TEM)-CD45RA+ (TEMRA) subset. Importantly, Ty21a immunization elicited Salmonella Typhi-responsive LPMC CD4+ T cells in all major TM subsets [interferon (IFN)γ and interleukin (IL)-17A in TEM; IFNγ and macrophage inflammatory protein (MIP)1β in T central/memory (TCM); and IL-2 in TEMRA]. Subsequently, we analyzed LPMC S. Typhi-responsive CD4+ T cells in depth for multifunctional (MF) effectors. We found that LPMC CD4+ TEM responses were mostly MF, except for those cells exhibiting the characteristics associated with IL-17A responses. Finally, we compared mucosal to systemic responses and observed that LPMC CD4+S. Typhi-specific responses were unique and distinct from their systemic counterparts. This study provides the first demonstration of S. Typhi-specific CD4+ TM responses in the human TI mucosa and provides valuable information about the generation of mucosal immune responses following oral Ty21a immunization.

Attenuated Oral Typhoid Vaccine Ty21a Elicits Lamina Propria and Intra-Epithelial Lymphocyte Tissue-Resident Effector Memory CD8 T Responses in the Human Terminal Ileum

Tissue-resident memory T cells (T_RM) are newly defined memory T cells (T_M) distinct from circulating T_M subsets which have the potential to mount rapid protective immune responses at the site of infection. However, very limited information is available regarding the role and contribution of T_RM in vaccine-mediated immune responses in humans at the site of infection. Here, we studied the role and contribution of tissue resident memory T cells (T_RM) located in the terminal ileum (TI) (favored site of infection for S. Typhi) following oral Ty21a immunization in humans. We examined TI-lamina propria mononuclear cells (LPMC) and intra-epithelial lymphocytes (IEL) CD8+ T_RM subsets obtained from healthy volunteers undergoing medically-indicated colonoscopies who were either immunized with Ty21a or unvaccinated. No significant differences in the frequencies of LPMC CD8+ T_RM and CD8+CD69+CD103– T cells subsets were observed following Ty21a-immunization. However, LPMC CD8+ T_RM exhibited significantly higher levels of cytokines (IFN-γ, IL-17A, and TNF-α) ex-vivo in Ty21a-vaccinated than in unvaccinated volunteers. LPMC CD8+ T_RMS. Typhi-specific responses were evaluated using S. Typhi-infected targets and found to produce significantly higher levels of S. Typhi-specific IL-17A. In contrast, LPMC CD8+CD69+CD103- T cells produced significantly increased S. Typhi-specific levels of IFN-γ, IL-2, and IL-17A. Finally, we assessed CD8+ T_RM in IEL and observed that the frequency of IEL CD8+ T_RM is significantly lower following Ty21a immunization. However, ex-vivo IEL CD8+ T_RM elicited by Ty21a immunization spontaneously produced significantly higher levels of cytokines (IFN-γ, IL-17A, IL-2, and TNF-α). This study provides the first demonstration of the effect of oral Ty21a vaccination on CD8+ T_RM subsets (spontaneous and S. Typhi-specific) responses in the LPMC and IEL compartment of the human terminal ileum mucosa, contributing novel information to our understanding of the generation of mucosal immune responses following oral Ty21a-immunization.

The influence of infliximab and adalimumab on the expression of apoptosis-related proteins in lamina propria mononuclear cells and enterocytes in Crohn's disease - an immunohistochemical study

BACKGROUND AND AIMS

The aim of this study was to assess the influence of anti-TNF agents on the expression of apoptosis-related proteins in Crohn's disease (CD) patients.

METHODS

The clinical, biochemical and endoscopic activity of CD was assessed with the use of tissue sampling before the initiation of therapy and after induction doses of infliximab and adalimumab. Additionally, the immunohistochemical expression of active caspase 3, TNFR1, Fas, Bcl-2, Bax, CD4 and CD8 proteins was estimated. Patients achieving deep remission were considered as responders.

RESULTS

Of the 35 patients qualified for the study, 60% achieved deep remission. In those patients, a significant decrease in the number of CD4 and CD8 positive cells was noted. Also observed was a significant increase in the expression of active caspase 3 in lamina propria mononuclear cells, which correlated with an increase of the pro-apoptotic Bax/Bcl-2 ratio. No change in Fas and TNFR1 expression was observed in those cells. Moreover, there was a significant decrease in active caspase 3 expression in enterocytes, observed independently of the Bax/Bcl-2 ratio. This correlated with a change in TNFR1 expression. No significant changes in the expression of the investigated proteins were noted in non-responders group.

CONCLUSIONS

The efficacy of anti-TNF antibodies is, at least partly, dependent on apoptosis modulation. In lamina propria mononuclear cells, the increase of apoptosis is probably the result of the induction of the intrinsic pathway mediated by Bcl-2 family proteins. In enterocytes - the decrease of apoptosis is mediated by the extrinsic pathway, probably via TNFR1.