*2.8. Flow Cytometry*

The expression of co-stimulatory molecules was assessed by flow cytometry. moDCs were seeded at a density of 1 <sup>×</sup> <sup>10</sup><sup>5</sup> cells per mL in a 24-well plate and incubated with either 1 µg/mL of Bet v 1 bound to 100 µg/mL of SiNP or 100 µg/mL of SiNP without Bet v 1 for 24 h at 37 ◦C and 5% CO2. The cells were then collected and stained for α-HLA-DR APC (Invitrogen, Waltham, MA, USA), Fixable Viability Dye eFluor506 (eBioscience, Waltham, MA, USA), α-CD1a BV421 (Biolegend, San Diego, CA, USA), α-CD86 PE (eBioscience), α-CD40 FITC (Biolegend), and α-CD83 PE-Cy™7 (BD Bioscience, Heidelberg, Germany). The cells were then fixed by adding 4% PFA (Sigma) solution in PBS, before sample acquisition using the FACS Canto II flow cytometer (BD Biosciences). The data thus obtained were analyzed using the FlowJo X 10.0.7r2 software. The data are presented in relation to the controls, which has been obtained by excluding the dead cells, nanoparticles, and doublets. The gating strategy is shown in Figure S2, in addition to the fluorescence minus one (FMO) control in Figure S3.
