CCR9-CCL25 mediated plasmacytoid dendritic cell homing and contributed the immunosuppressive microenvironment in gastric cancer

OBJECTIVES

Plasmacytoid dendritic cells (pDCs) play a crucial role in the microenvironment of tumor. Evidences has been shown that chemokine receptor 9 (CCR9) is an important molecule that attracts pDCs homing to the digestive tract and the latter are involved in the formation of digestive tract immune tolerance. The aim of this study was to explore the role of CCR9-CCL25 interaction in pDC-mediated immunosuppression microenvironment of gastric cancer (GC).

MATERIALS AND METHODS

Regulatory T cells (Tregs) and pDCs were detected by immunohistochemistry. CCR9, which expressed on pDC was visualized by immunofluorescence. Western Blot was applied to evaluate the expression of CCL-25. Total pDCs, CCR9+pDCs, CCR9-pDCs, total Tregs, inducible costimulator + (ICOS) Tregs and ICOS-Tregs in peripheral blood and draining lymph nodes were analyzed by flow cytometry. Plasma concentration of the cytokines were measured by enzyme-linked immunosorbent assay RESULTS: Total Tregs, pDCs and CCR9+pDCs were higher in GC tissue. CCL-25 was over-expressed in carcinoma tissue. Peripheral total pDCs, CCR9-pDCs, total Tregs, ICOS+ Tregs, ICOS- Tregs were significantly increased in GC patients. More total pDCs, CCR9+ pDCs, total Tregs, ICOS+ Tregs were found in metastatic lymph nodes. Plasma concentrations of IL-6 and IL-10 were significantly higher in GC patients. More CCR9+ pDCs were found infiltrating carcinoma tissue in patients with later T staging and lymph node metastasis and conferred a poor prognosis.

CONCLUSION

CCR9-CCL25 interaction might play an important role in mediating PDC homing to metastatic lymph nodes and carcinoma tissue, which contributed to the formation of tumor immunosuppressive microenvironment and poor prognosis.

Impaired CCR9/CCL25 signalling induced by inefficient dendritic cells contributes to intestinal immune imbalance in nonalcoholic steatohepatitis

Abnormal crosstalk between gut immune and the liver was involved in nonalcoholic steatohepatitis (NASH). Mice with methionine choline-deficient (MCD) diet-induced NASH presented an imbalance of pro-(IL-6 and IFN-γ) and anti-inflammatory cytokines (IL-10) in the intestine. We also clarified that the ratio of CD4+ T cells and found that the NASH mesenteric lymph node (MLN) presents decreased numbers of CD4+Th17 cells but increased numbers of CD4+CD8+FoxP3+ regulatory T cells (Tregs). Furthermore, the intestinal immune imbalance in NASH was attributed to impaired gut chemokine receptor 9 (CCR9)/chemokine ligand 25 (CCL25) signalling, which is a crucial pathway for immune cell homing in the gut. We also demonstrated that CD4+CCR9+ T cell homing was dependent on CCL25 and that the numbers and migration abilities of CD4+CCR9+ T cells were reduced in NASH. Interestingly, the analysis of dendritic cell (DC) subsets showed that the numbers and retinal dehydrogenase (RALDH) activity of CD103+CD11b+ DCs were decreased and that the ability of these cells to upregulate CD4+ T cell CCR9 expression was damaged in NASH. Taken together, impaired intestinal CCR9/CCL25 signalling induced by CD103+CD11b+ DC dysfunction contributes to the gut immune imbalance observed in NASH.