Dendritic cells produce IL-12 and direct the development of Th1 cells from naive CD4+ T cells.

TLDR

Dendritic cells are antigen‑presenting cells uniquely capable of strongly stimulating primary antigen‑specific responses in vitro and in vivo. The study demonstrates that dendritic cells produce IL‑12, a key cytokine that drives the development of IFN‑γ–producing T cells. The authors showed that Th1 differentiation from CD4+ T cells requires IL‑12 produced by dendritic cells, confirmed by IL‑12 p40 immunofluorescence staining. Dendritic cells induce Th1 differentiation of antigen‑specific naive CD4+ T cells, particularly when IL‑4–producing cells are absent, underscoring their role in generating IFN‑γ–producing cells for cell‑mediated immunity.

Abstract

Abstract Dendritic cells are APCs that are unique in their potency to stimulate proliferation of primary Ag-specific responses in vitro and in vivo. In this study, we demonstrate that dendritic cells can produce IL-12, a dominant cytokine involved in the development of IFN-gamma-producing T cells. This finding resulted from our observations that dendritic cell-induced Th1 development from total CD4+ T cells upon neutralization of endogenous levels of IL-4 was IL-12-dependent. Furthermore, we demonstrate that dendritic cells can induce the development of Th1 cells from Ag-specific naive LECAM-1bright CD4+ T cells obtained from alpha beta-TCR transgenic mice, provided that CD4+ LECAM-1dull T cells, which produce significant levels of IL-4, are not present in the primary cultures. Production of IL-12 by dendritic cells was confirmed by positive immunofluoresence staining with Abs specific for the inducible IL-12 p40 subunit. This suggests that in addition to inducing proliferation and clonal expansion of naive T cells, dendritic cells, by their production of IL-12, play a direct role in the development of IFN-gamma-producing cells that are important for cell-mediated immune responses.