Infiltration of [Formula: see text] T cells, IL-17 [Formula: see text] T cells and FoxP3 [Formula: see text] T cells in human breast cancer

BACKGROUND: Tumor-infiltrating lymphocytes (TILs) have a strong prognostic value in various forms of cancers. These data often refer to use of the pan-T cell marker CD3, or the cytotoxic T lymphocyte marker CD8 [Formula: see text]. However, T cells are a heterogeneous group of cells with a wide array of effector mechanisms ranging from immunosuppression to cytotoxicity. OBJECTIVE: In this study we have investigated the prognostic effects of some unconventional T cell subtypes in breast cancer; [Formula: see text] T cells, IL-17 [Formula: see text] T cells and FoxP3 [Formula: see text] T cells (T [Formula: see text]) in relation to the conventional CD3 and CD8 [Formula: see text] T cell markers. METHODS: This was done using immunohistochemistry on a human breast cancer tissue microarray consisting of 498 consecutive cases of primary breast cancer. RESULTS: Infiltration of [Formula: see text] T cells and T cell infiltration in general (CD3), correlated with a good prognosis, while T [Formula: see text] infiltration with a worse. Infiltration of [Formula: see text] T cells was associated with a significantly improved clinical outcome in all breast cancer subtypes except triple negative tumors. Only infiltration of either CD3 [Formula: see text] or CD8 [Formula: see text] cells was independently associated with better prognosis for all breast cancer patients. CONCLUSIONS: This study sheds further light on the prognostic impact of various T cell subtypes in breast cancer.