Fig. 2

SARS-CoV-2 spike RBD protein enhanced the severity of LPS-induced inflammation in the lung tissues. The proinflammatory cytokines (A). TNF-α, B IL-1β and (C) IL-6 in the BALF were determined by ELISA (n = 4–6 for each group). D The concentrations of MPO in the BALF were determined by ELISA (n = 5 for each group). N.D. indicates not detectable. E The protein expression levels of MPO were determined by western blot analysis. F The macrophage infiltration in the lung tissues was determined by IHC, and the representative images were shown. CD68 was used as the maker for the staining of macrophage. The upper panel, 100×, scale bar = 100 μm; the bottom panel, 400×, scale bar = 100 μm. Data are shown as mean ± S.D., *P < 0.05, **P < 0.01, and N.S. indicates not significant