Increased expression of CD86 and reduced production of IL-12 and IL-10 by monocyte-derived dendritic cells from allergic asthmatics and their effects on Th1- and Th2-type cytokine balance

Background: In allergic asthma, allergen-specific T cells have a Th2-biased phenotype, and it is thought that dendritic cells (DCs) contribute to the induction of allergic immune responses. Therefore, we hypothesized that DCs from allergic asthmatics and healthy donors differ with regard to their preference to induce Th1 or Th2 immune responses.

Objectives: To investigate differences in DC-expressed costimulatory molecules and DC-secreted cytokines between allergic asthmatics and healthy donors, and their influence on the Th1- and Th2-type cytokine balance.

Methods: Circulating monocytes from patients with allergic asthma and healthy donors were cultured with GM-CSF and IL-4, respectively, for 5 days and subsequently with lipopolysaccharide for 2 days to create mature DCs (mDCs). CD1a, CD83, CD40 and CD86 expression on mDCs was examined using a fluorescence-activated cell sorter. IL-12 and IL-10 secreted by mDCs were measured by ELISA. Naïve cord blood T cells were primed by mDCs from two groups, and IL-4 and IFN-gamma production by polarized T-helper cells (Th) was measured by ELISA.

Results: (1) CD86 expression on mDCs from allergic asthmatics was higher than that from healthy donors. (2) IL-12, IL-12p40 and IL-10 production by mDCs from allergic asthmatics was significantly lower than that from healthy donors, respectively. (3) IL-4 production by Th cells primed by mDCs from allergic asthmatics was increased compared with that from healthy donors.

Conclusions: mDCs from allergic asthmatics preferentially priming naïve T cells towards Th2-cell development might be due to increased expression of CD86 and reduced production of IL-12 and IL-10.