Figure EV4. Plasmacytoid DC‐secreted cytokines produced post SARS‐CoV‐2 sensing, protect epithelial cells from infection.

• A–C
  To assess whether pDCs could mount protection against SARS‐CoV‐2, conditioned medium from SARS‐CoV‐2‐exposed pDC cultures (d3 post inoculation with 1 MOI) was added to A549 hACE2 lung epithelial cells (A) or Calu‐3 (B) cultures followed by SARS‐CoV‐2 inoculation. The cell cultures were conditioned with normal medium ( ‐, grey), pDC supernatant (pDC mock, blue), or SARS‐CoV‐2‐inoculated pDC supernatant (pDC SARS‐2, purple), prior to infection with SARS‐CoV‐2 (0.1 MOI). Supernatants were collected and viral outgrowth was determined 48 h post infection. To investigate a potential dose‐response, SARS‐CoV‐2‐inoculated pDC supernatant was 3‐fold serially diluted prior to addition to Calu‐3 cells (purple‐pink gradient, B). To determine the involvement of type I IFNs, Calu‐3 cells and SARS‐CoV‐2‐inoculated pDC supernatants were pre‐treated with antibodies blocking the type I IFN receptor and antibodies neutralizing type I IFNα (IFN‐I block) or isotype control antibodies (isot ctrl), prior to the addition of conditioned medium to the cells and infection (C). All antibodies were used at a final concentration of 10 μg/ml.

Data information: Bars and lines represent median values and symbols represent individual HSPC‐pDC donors (n = 3–5) Equal symbols represent equal donors. Statistical significance was determined using the ratio paired student T test (A, B) and one‐tailed paired student T test (C). *P < 0.05, ***P < 0.001.