Fig 2: C9 inhibits MRGPRX2-mediated MC degranulation in LAD2 cells without affecting the C3aR response. (A) LAD2 cells were preincubated with C9 and inactive analog C7 (1 µM, for 5 min) then exposed to agonists at the indicated concentrations, and degranulation was assayed by measuring the release of ß-hexosaminidase. (B, C) Cells were stimulated with SP (0.3 µM) or C3a (3 nM) for 5 min in the presence or absence of C9 or C7. Cell surface expression of CD107a and CD63 were determined by flow cytometry. Representative histograms of three independent experiments are shown. (D, E) The mean fluorescent intensity (MFI) levels of CD107a and CD63 are shown. Data are expressed as mean ± SEM. Statistical significance was determined by two-way ANOVA test at a value ***P < 0.001 and ****P < 0.0001.

Fig 3: C9 inhibits the upregulation of cell surface expression of CD107a and CD63 in response to SP in human skin-derived MCs. (A-C) Cells from three donors were preincubated with buffer or C9 (1 µM, 5 min), stimulated with SP (0.3 µM) or Fc?RIa-aggregation antibody, IgER-CL (0.3 µg/ml) for an additional 5 min and cell surface expression of CD107a and CD63 was determined by flow cytometry. Representative histograms of CD107a and CD63 expression are shown. (D–F) The mean fluorescent intensity (MFI) levels of CD107a and CD63 are shown. Data are expressed as mean ± SEM. Statistical significance was determined by two-way ANOVA test at a value **P < 0.01, ***P < 0.001, and ****P < 0.0001.