High level IL-12 production by murine dendritic cells: upregulation via MHC class II and CD40 molecules and downregulation by IL-4 and IL-10.

TLDR

Dendritic cells produce IL‑12 when they interact with CD4⁺ T cells. The study investigates how IL‑12 production is induced and regulated. IL‑12 production was quantified by qPCR, in situ hybridization for p40, and ELISA for the p70 heterodimer. Ligation of CD40 or MHC class II independently induces IL‑12, with the CD40/CD40L pathway being quantitatively dominant; IL‑4 and IL‑10 downregulate production, and activated CD40‑ligand‑expressing helper T cells can trigger high levels of bioactive IL‑12 even without antigen recognition, underscoring the role of CD40/CD40L in Th1 responses.

Abstract

We have shown previously that dendritic cells (DC) produce IL-12 upon interaction with CD4+ T cells. Here we ask how this IL-12 production is induced and regulated. Quantitative PCR and in situ hybridization for IL-12 p40 and an ELISA specific for the p70 heterodimer were used to determine IL-12 production. We demonstrate that ligation of either CD40 or MHC class II molecules independently trigger IL-12 production in DC, and that IL-12 production is downregulated by IL-4 and IL-10. The levels of bioactive IL-12 that can be released by triggering with an anti-CD40 mAb or with a T cell hybridoma are high (range 260-4700 pg/ml from 1 X 10(6) DC in 72 h). The CD40-mediated pathway indicates that IL-12 production is induced in DC upon interaction with activated, CD40 ligand-expressing helper T cells, even in the absence of cognate antigen recognition. Side-by-side comparison of IL-12 production, and blocking experiments employing an anti-CD40 ligand mAb, suggest that the CD40-mediated pathway is quantitatively more significant than induction via the MHC class II molecule. The importance of the CD40/CD40 ligand interaction for IL-12 induction in DC likely contributes to the recent finding that mice lacking the CD40 ligand are impaired in mounting Th1 type cell-mediated immune responses.