Infiltration of effector regulatory T cells predicts poor prognosis of diffuse large B-cell lymphoma, not otherwise specified.

Regulatory T cells (Tregs) specifically express the transcription factor forkhead box P3 (FOXP3) and contribute to tumor progression. FOXP3-positive cells have been recently proven to be heterogeneous in phenotype and function, including effector Tregs (eTregs), naïve Tregs, and non-Tregs, which harbor no suppressive function. Therefore, it is crucial to investigate the "true Treg (eTreg)" population, rather than the entire FOXP3 population, with regards to their effect on tumor immunity. In particular, in diffuse large B-cell lymphoma, not otherwise specified (DLBCL, NOS), FOXP3-positive cells correlated with a better prognosis. The present study sought to evaluate the relationship between the prognosis of DLBCL, NOS patients and the infiltration of true Tregs by employing dual immunostaining with FOXP3 and cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4). CTLA-4 is a negative immunomodulatory known to be expressed by eTregs, but not by non-Tregs. Lymph nodes from 82 nodal DLBCL, NOS patients were stained with anti-FOXP3 and anti-CTLA-4 antibodies. A high infiltration of FOXP3-positive cells was associated with a significantly better prognosis than patients with low levels of FOXP3-positive cells for overall survival (OS) (P = .0233). In sharp contrast, a high infiltration of FOXP3/CTLA-4 double-positive cells was significantly associated with a poor prognosis than patients with low levels of FOXP3/CTLA-4 double-positive cells for OS (P = .0121) and progression-free survival (P = .0171), independent of the international prognostic index. FOXP3/CTLA-4 double-positive cells, eTregs, play an important role in DLBCL, NOS progression.