A Magnetic Bead-Based Negative Selection and Flow Cytometry Protocol for Evaluating Licochalcone A-Mediated Inhibition of Murine Th17 Differentiation.

Naïve CD4⁺ T cell differentiation into Th17 cells is a key driver of autoimmune and chronic inflammatory skin diseases. Licochalcone A (Lico-A), a bioactive flavonoid from Glycyrrhiza inflata, exhibits anti-inflammatory activity in dermatological applications, yet its direct effect on Th17 commitment remains poorly characterized due to a lack of standardized evaluation protocols. To address this, this protocol establishes a complete in vitro workflow to assess Lico-A's inhibition of naïve CD4⁺ T cell differentiation into Th17 cells. The procedure comprises: isolation of highly pure naïve CD4⁺ T cells from mouse spleens via magnetic bead-based negative selection (>90% purity); induction of Th17 polarization under anti-CD3/CD28 costimulation with a defined cytokine cocktail (TGF-β, IL-6, IL-1β, IL-23, and IL-2, supplemented with anti-IL-4 and anti-IFN-γ); treatment with 500 nM Lico-A throughout the 72-hour polarization period; and quantification of differentiation efficiency by intracellular IL-17A staining followed by flow cytometric analysis. Critical controls, including parallel cell viability staining, are incorporated to distinguish specific inhibition of differentiation from nonspecific cytotoxicity. In a representative experiment, Lico-A reduced the proportion of CD4⁺IL-17A⁺ cells from 45.8% to 11.5% without compromising cell viability. This standardized protocol offers a reproducible platform for screening immunomodulatory compounds and investigating their mechanisms in Th17-associated inflammatory skin diseases. However, disease-relevant therapeutic effects require validation in appropriate in vivo animal models.