CD14++ CD16− monocytes are the main source of 11β-HSD type 1 after IL-4 stimulation

•IL-4 stimulated CD14 monocytes are the major source of 11β-HSD1•Maturation of CD14 to M1 phenotype is prevented by IL-4 stimulation•11β-HSD1 production is independent of CD14 maturation towards the M2 phenotype

The anti-inflammatory actions of IL-4 are well established through earlier findings. However, the exact mechanism it uses to downregulate the pro-inflammatory cytokine production through monocytes and macrophages is poorly understood. In this study, we examined the effect of IL-4 in the induction of 11β-HSD1 in the two main classes of monocytes, CD14++ CD16− (CD14) and CD14+ CD16+ (CD16). Peripheral Blood Mononuclear Cells (PBMCs) were isolated from 17 healthy donors and were sorted into CD14 and CD16 subpopulations using cell sorting. Effect of IL-4 on 11β-HSD1-enzyme activity was measured in sorted and unsorted monocytes using Homogeneous Time-Resolved Fluorescence (HTRF) and M1/M2 polarization analysis was performed by flow cytometry. Our results indicate that CD14 cells are the major source of 11β-HSD1 enzyme after IL-4 stimulation and that M2 phenotype is not a pre-requisite for its synthesis.