title: Tumor-infiltrating T lymphocytes: friends or foes?
abstract: The prognostic significance of tumor-infiltrating lymphocytes (TILs) has been a longstanding topic of debate. In cases where TILs have improved patient outcome, T lymphocytes are recognized as the main effectors of antitumor immune responses. However, recent studies have revealed that a subset of CD4(+) T cells, referred to as CD4(+)CD25(+) regulatory T cells (Treg), may accumulate in the tumor environment and suppress tumor-specific T-cell responses, thereby hindering tumor rejection. Hence, predicting tumor behavior on the basis of an indiscriminate evaluation of tumor-infiltrating T cells may result in inconsistent prognostic accuracy. The presence of infiltrating CD4(+)CD25(+) Treg may be detrimental to the host defense against the tumor, while the presence of effector T lymphocytes, including CD8(+) T cells and non-regulatory CD4(+) helper T cells may be beneficial. Enhanced recruitment of antitumor effector T lymphocytes to tumor tissue in addition to inhibition of local Treg, may therefore be an ideal target for improving cancer immunotherapy. This article reviews the antitumor functions of T-lymphocytes, with special attention given to CD4(+) regulatory T-cells within the tumor environment.
authors.affiliation: 1Department of Pathology and Committee on Immunology, University of Chicago, Chicago, IL 60637, USA. pingyu@uchicago.edu
authors.forename: Ping
authors.initials: P
authors.lastname: Yu
authors.forename: Yang-Xin
authors.initials: YX
authors.lastname: Fu
mesh_terms: D015496:CD4-Positive T-Lymphocytes / Q000276:immunology* / Q000473:pathology; D006801:Humans; D016246:Lymphocytes, Tumor-Infiltrating / Q000276:immunology* / Q000473:pathology; D009369:Neoplasms / Q000276:immunology* / Q000473:pathology; D011379:Prognosis; D016176:T-Lymphocyte Subsets / Q000276:immunology / Q000473:pathology; D050378:T-Lymphocytes, Regulatory / Q000276:immunology* / Q000473:pathology