Synergistic effect of Dermatophagoides pteronyssinus allergens and dexamethasone on the expression of CD163 by peripheral blood mononuclear cells

Background The CD163 is a marker of monocyte/macrophage anti-inflammatory function. Its soluble form (sCD163) also exert anti-inflammatory activities including inhibition of T cell proliferation. Objective To evaluate the effect of dexamethasone (Dx) and Dermatophagoides pteronyssinus (Dp) on ex vivo production of sCD163 by peripheral blood mononuclear cells (PBMCs). Methods PBMCs from 26 allergic asthma patients (AAs) and 12 non-atopic healthy controls (HCs) were cultured with Dp, Dx, Dp + Dx or without any stimulation for up to 144 h (T144). Concentration of sCD163, interleukin (IL) -6 and IL-10 in PMBC culture supernatants was evaluated using ELISA. The mRNA expression of CD163 by PBMCs was estimated using quantitative PCR (qPCR). Results At T144 the median concentration of CD163 in unstimulated PBMC cultures of AAs was greater than that in HCs (p = 0.008). Concomitant application of Dp and Dx resulted in a synergistic effect reflected by a dramatic increase of sCD163 concentration both in HCs (p = 0.0002) and AAs (p < 0.0001). Also a synergistic effect of Dp and Dx on CD163 mRNA expression was seen at T24 and T48 but not at T6 or T12. Among asthmatic patients the effect of Dx on sCD163 production was attenuated in severe in comparison to mild-to-moderate AAs (p = 0.0007). Moreover, Dp-induced production of IL-6 but not IL-10 was inhibited by Dx (p < 0.0001). Inhibition of IL-10 decreased sCD163 concentration by more than 50%. Conclusions Dx-triggered upregulation of anti-inflammatory CD163 expression by monocytes is synergistic with endogenous mechanisms involved in the resolution of Dp-induced inflammation. This effect is impaired in severe asthma patients.