Yonago Acta medica 2010;53:009–016
NKG2D+CD4+ T Cells with Immune Suppressive Property Increase in Patients with Colorectal Cancer
Manabu Yamamoto, Hiroaki Saito, Kyoichi Kihara, Kuniyuki Katano and Masahide Ikeguchi
Division of Surgical Oncology, Department of Surgery, School of Medicine, Tottori University Faculty of Medicine, Yonago 683-8504, Japan
Some studies suggest that small populations of CD4+ T cells with activation-independent, constitutive, NKG2D expression are found in normal peripheral blood and have immune suppressive properties. The present study was designed to investigate NKG2D expression on CD4+ T lymphocytes and its relationship to immune evasion in colorectal cancer patients. We examined NKG2D expression on both circulating and tumor infiltrating CD4+ and CD8+ T cells or NK cells and evaluated it by multicolor flow cytometry. Furthermore, intracellular cytokine staining was carried out to determine the cytokine profile of NKG2D+CD4+ T cells in colorectal cancer patients. As a result, NKG2D expression on circulating and tumor-infiltrating CD8+ T cells and NK cells was downregulated in colorectal cancer patients. On the other hand, circulating and tumor-infiltrating NKG2D+CD4+ T cells increased in colorectal cancer patients. NKG2D+CD4+ T cells produced more immune suppressive cytokines, such as interleukin-10 and transforming growth factor-1β, than did NKG2D-CD4+ T cells. Increased NKG2D+CD4+ T cells as well as decreased NKG2D expression on CD8+ T cells and NK cells may be one of the key mechanisms responsible for immune evasion by tumors in colorectal cancer.
Key words: CD4+ T lymphocyte; colorectal cancer; NKG2D
