Antitumor immune response changes drastically during the development and progression of cancers. We demonstrated that the prevalence of FOXP3⁺ regulatory T cells is increased in pancreatic ductal adenocarcinoma and is an independent prognostic factor. Furthermore, infiltration of FOXP3⁺ regulatory T cells is closely correlated to the progression of premalignant lesions of pancreatic cancer, suggesting that FOXP3⁺ regulatory T cells play a role in controlling the immune response in pancreatic multistep carcinogenesis. The photograph shows newly established monoclonal antibody detecting FOXP3 (green) in CD4⁺CD25⁺ regulatory T cells and few CD8⁺ T cells (red) of lymph node in formalin-fixed paraffin-embedded section. For further details, please see Hiraoka et al. on page 5423 in this issue.

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