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. Author manuscript; available in PMC: 2022 May 1.
Published in final edited form as: J Invest Dermatol. 2020 Oct 13;141(5):1286–1296.e4. doi: 10.1016/j.jid.2020.09.017

Figure 1. MRGPRX2 is the codeine receptor on human skin MCs.

Figure 1.

(a–c) Skin MCs ex vivo were stimulated with codeine, and (a) net histamine release (stimulated release–spontaneous release; in percentage of total histamine) was assessed after 30 minutes; mean ± SEM and n = 8. (b) CD107a externalization was determined by flow cytometry after the indicated times, representative of two independent experiments. (c) β-Hexosaminidase release served to calculate EC50. The net release for each concentration was normalized to the maximum; mean ± SD, n = 6. (d–i) Cells were subjected to MRGPRX2-specific siRNA or nontarget siRNA for 2 days. (d) MRGPRX2 surface expression; mean ± SEM of net MFI (MFI MRGPRX2–MFI isotype) for MRGPRX2 siRNA normalized to nontarget siRNA; n = 10. (e) Representative histograms, blue: MRGPRX2, red: isotype. (f–i) Net histamine release triggered by C48/80 (10 µg/ml), SP (30 µM), codeine (50 µg/ml), and IgER-CL (29C6, 0.5 µg/ml); mean ± SEM and n = 7–8. MRGPRX2-specific siRNA reduced degranulation to 29.8 ± 12.8% (codeine), 36.2 ± 12.0% (C48/80), 40.0 ± 11.9% (SP). **P < 0.01, ***P < 0.001, ****P < 0.0001. C48/80, compound 48/80; CL, crosslinking; EC50, half maximal effective concentration; IgER, IgE receptor; MC, mast cell; MFI, mean fluorescence intensity; min, minute; siRNA, small interfering RNA; SP, substance P.