RESUMO
Tumor growth promotes the expansion of CD4+CD25+ regulatory T (T reg) cells that counteract T cell-mediated immune responses. An inverse correlation between natural killer (NK) cell activation and T reg cell expansion in tumor-bearing patients, shown here, prompted us to address the role of T reg cells in controlling innate antitumor immunity. Our experiments indicate that human T reg cells expressed membrane-bound transforming growth factor (TGF)-beta, which directly inhibited NK cell effector functions and down-regulated NKG2D receptors on the NK cell surface. Adoptive transfer of wild-type T reg cells but not TGF-beta-/- T reg cells into nude mice suppressed NK cell-mediated cytotoxicity, reduced NKG2D receptor expression, and accelerated the growth of tumors that are normally controlled by NK cells. Conversely, the depletion of mouse T reg cells exacerbated NK cell proliferation and cytotoxicity in vivo. Human NK cell-mediated tumor recognition could also be restored by depletion of T reg cells from tumor-infiltrating lymphocytes. These findings support a role for T reg cells in blunting the NK cell arm of the innate immune system.
Assuntos
Imunidade Inata/imunologia , Células Matadoras Naturais/imunologia , Ativação Linfocitária/imunologia , Neoplasias/metabolismo , Subpopulações de Linfócitos T/imunologia , Linfócitos T Reguladores/imunologia , Fator de Crescimento Transformador beta/metabolismo , Animais , Linhagem Celular Tumoral , Proliferação de Células , Citocinas/metabolismo , Testes Imunológicos de Citotoxicidade , Citometria de Fluxo , França , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Subfamília K de Receptores Semelhantes a Lectina de Células NK , Receptores Imunológicos/metabolismo , Receptores de Células Matadoras Naturais , Linfócitos T Reguladores/metabolismo , Fator de Crescimento Transformador beta/imunologiaRESUMO
The mechanisms through which regulatory T cells accumulate in lymphoid organs of tumor-bearing hosts remain elusive. Our experiments indicate that the accumulation of CD4+CD25+ regulatory T cells (T reg cells) expressing FoxP3 and exhibiting immunosuppressive function originates from the proliferation of naturally occurring CD25+ T cells and requires signaling through transforming growth factor (TGF)-beta receptor II. During tumor progression, a subset of dendritic cells (DCs) exhibiting a myeloid immature phenotype is recruited to draining lymph nodes. This DC subset selectively promotes the proliferation of T reg cells in a TGF-beta-dependent manner in mice and rats. Tumor cells are necessary and sufficient to convert DCs into regulatory cells that secrete bioactive TGF-beta and stimulate T reg cell proliferation. In conclusion, tumor expansion can stimulate T reg cells via a specific DC subset.
