The subsets of dendritic cells and memory T cells correspond to indoleamine 2,3-dioxygenase in stomach tumor microenvironment.

The abnormal distributions of memory T cells (Tm) and dendritic cells (DC) in stomach cancer are not well understood. Indoleamine 2,3-dioxygenase (IDO), produced by DC, may be an important enzyme affecting function and proliferation of Tm. In this study, IDO expression was examined by immunohistochemical staining. The subsets of Tm and DC were counted by flow cytometry. The percentages of CD4 + Tm and CD4 + central Tm (Tcm) were lower in tumor tissues than in normal tissues (P < 0.05), while the CD4 + effector Tm (Tem) and CD8 + Tem percentages were higher in tumor tissues (P < 0.05). The ratio of myeloid DC (DC1)/plasmacytoid DC (DC2) was significantly lower in tumor tissues (P = 0.009). The high expression of IDO was more frequently observed in tumor tissues (P = 0.001). The percentages of CD4 + Tm and CD8 + Tm were positively associated with DC1 percentage and ratio of DC1/DC2 (P < 0.05). The higher CD8 + Tcm percentage was associated with higher DC2 percentage (P = 0.025). The patients with high IDO expression had significantly lower CD4 + Tm (P = 0.012) and CD8 + Tm percentages (P = 0.033), but higher CD8 + Tem percentage (P < 0.01). Concerning on clinicopathologic features, the higher DC2 percentage was associated with larger tumor size (P = 0.019). The CD4 + Tm and CD8 + Tem percentages were significantly associated with clinical stage and lymph node metastasis; the high IDO expressions were significantly associated with deeper tumor invasion (P = 0.016) and lymph node metastasis (P = 0.038). Thus, DC subsets, Tm subsets, and IDO expression were correlated with each other. They were associated with the established clinicopathologic features, such as tumor size, depth of invasion, lymph node metastasis, and clinical stage.