Nasal B and MAIT Cell Immunophenotyping

Immunophenotyping of nasal B and MAIT cells obtained by curettes was performed as described previously (29 (link)). In brief, cells were dislodged from curettes and stained with LIVE/DEAD Fixable Aqua Dead Cell Stain (Thermo Fisher Scientific) and an antibody cocktail containing, among others, Epcam-PE, HLADR-PE/Cy7, CD66b-FITC, CD19-BV650 (all BioLegend), CD3-APC/Cy7, CD14-Percp/Cy5.5 (BD Biosciences), and CD45-PACOrange (Thermo Fisher Scientific) for B cells, while the cocktail for MAIT cells also included CD8–BV785 and TCRva7.2-BV711 or TCRva7.2–PE/Texas Red and CD45-BV510 (BioLegend). Samples were acquired on a BD LSR II flow cytometer and analyzed using FlowJo X. Fluorescence-minus-one controls for each of the included antibodies were used to validate results during setup of all of the panels used. Samples with less than 500 immune cells or 250 epithelial cells (11.9% of all nasal samples) were excluded from further analysis. A full list of all antibodies used for flow cytometry is provided in Supplemental Table 2).