Figure 12.

A human Lin⁻ CD123⁺ CD127^low endowed with innate lymphoid cells (ILC) features and migratory capabilities contributes to immunopathological hallmarks of psoriasis. Peripheral blood (PB) contains a Lin⁻ CD123⁺ population with a mixture lymphoid (in red: CD127^low CD7^low) and basophil markers expression (in purple: FcεR, CCR3, CD203^int 2D7^low) and is endowed with high migratory capabilities [cutaneous lymphocyte antigen (CLA) and CXCR4]. In steady state, this population possesses several ILC features (in blue: Lin⁻, CD132⁺, CD90⁺, CD161⁺, NFIL-3⁺, TCF-1⁺, Id2⁺, TOX⁺, PLZF⁺) and after activation with IL-3 increase this features. This population after PMA/Iono treatment downregulates CD123, is able to produce IL-8, IL-4, and IL-2, and diminish the basophil markers. A similar but specialized CD123^low population normally infiltrates barrier tissues, such as skin. We propose that CXCR4-SDF-1 is an important skin-homing mechanism under inflammatory conditions, particularly in psoriasis. The increase of the CD123^low population in the non-lesioned and lesioned skin of psoriasis patients supports its high migratory potential. Remarkably, the expression of IL-22 and particularly IL-17 by the CD123^low population in the skin of psoriasis patients strongly suggests that this population may contribute to the immunopathological hallmarks of a skin disease such as psoriasis.