Production of IL-12 by Human Monocyte-Derived Dendritic Cells Is Optimal When the Stimulus Is Given at the Onset of Maturation, and Is Further Enhanced by IL-4

Abstract

Dendritic cells produce IL-12 both in response to microbial stimuli and to T cells, and can thus skew T cell reactivity toward a Th1 pattern. We investigated the capacity of dendritic cells to elaborate IL-12 with special regard to their state of maturation, different maturation stimuli, and its regulation by Th1/Th2-influencing cytokines. Monocyte-derived dendritic cells were generated with GM-CSF and IL-4 for 7 days, followed by another 3 days ± monocyte-conditioned media, yielding mature (CD83+/dendritic cell-lysosome-associated membrane glycoprotein+) and immature (CD83−/dendritic cell-lysosome-associated membrane glycoprotein−) dendritic cells. These dendritic cells were stimulated for another 48 h, and IL-12 p70 was measured by ELISA. We found the following: 1) Immature dendritic cells stimulated with CD154/CD40 ligand or bacteria (both of which concurrently also induced maturation) secreted always more IL-12 than already mature dendritic cells. Mature CD154-stimulated dendritic cells still made significant levels (up to 4 ng/ml). 2) Terminally mature skin-derived dendritic cells did not make any IL-12 in response to these stimuli. 3) Appropriate maturation stimuli are required for IL-12 production: CD40 ligation and bacteria are sufficient; monocyte-conditioned media are not. 4) Unexpectedly, IL-4 markedly increased the amount of IL-12 produced by both immature and mature dendritic cells, when present during stimulation. 5) IL-10 inhibited the production of IL-12. Our results, employing a cell culture system that is now being widely used in immunotherapy, extend prior data that IL-12 is produced most abundantly by dendritic cells that are beginning to respond to maturation stimuli. Surprisingly, IL-12 is only elicited by select maturation stimuli, but can be markedly enhanced by the addition of the Th2 cytokine, IL-4.

Deficient IL-12p70 secretion by dendritic cells based on IL12B promoter genotype

“…IL-12p40 secretion by DCs proved to be highly variable, with a range from below the detection limit to 31 ng/ml ( Figure 1). Similar high inter-individual variation has been observed, but not explained previously 10,16,17 ; it may be due to separate effects on gene expression of the promoter and 3 0 UTR polymorphisms, or other as yet undefined elements. Analysis of p40 secretion in relationship to the IL12Bpro genotype is shown in Figure 1.…”

Gene transduction efficiency and maturation status in mouse bone marrow-derived dendritic cells infected with conventional or RGD fiber-mutant adenovirus vectors

“…[1][2][3] Furthermore, mature DCs increase the amount of IL-12 secretion, which is important for activation of cellular immunity, [41][42][43] and gain the ability to migrate to regional lymph nodes by changing the expression pattern of chemokine receptors. [40][41][42][43][44][45][46] Therefore, it is desirable for promoting the efficacy of DC-based immunotherapy that antigen delivery to DCs is accompanied by DC-maturation, which leads to optimal T-cell activation. Maturation can be triggered by multiple stimuli, including contact components of bacteria and viruses, proinflammatory cytokines, and CD40-CD40L signaling.…”

“…These chemokines are constitutively produced by stromal cells in lymph node. [40][41][42][43][44][45][46]56,57 The chemokine receptor expression patterns in DCs are tightly regulated as a function of maturation and account for the differences observed in the roles of immature and mature DCs. Therefore, DC-based immunotherapy should include ex vivo-matured DCs because migration of administered DCs from vaccination site to regional lymph node is an essential part of successful therapy.…”

A TaqI polymorphism in the 3′UTR of the IL-12 p40 gene correlates with increased IL-12 secretion

“…1 Whereas the p35 chain is constitutively expressed in many cell types, expression of IL-12 p40, and therefore the p70 heterodimer, occurs mainly in dendritic cells, macrophages and monocytes after one of several stimuli. [2][3][4] IL-12 plays a key role in the modulation of the immune response by providing the stimulus for CD4+ T cells and NK cells to differentiate towards Th1, IFNg secreting cells, which in general is associated with cell-mediated immunity. In this capacity, IL-12 plays a key role in the defense against intracellular microorganisms.…”