Fig. 5.

(a) Effect of anti-S2 Abs and IFN-γ on PBMC adherence to epithelial cells. A549 cells were cultured in 8-well glass chamber slides and treated with 25 ng of IFN-γ for 24 h. Cells were washed with PBS, and then cocultured with fresh human PBMC for 1 h in the presence or absence of 1 : 50 dilution of anti-S2 hyperimmune sera. Cell adhesion was observed using Liu's stain. The numbers of adherent cells were quantified in each tested culture. (b) Blockage of PBMC adherence to epithelial cells by spike peptides. Anti-S2 hyperimmune sera were preabsorbed with 10 µg S2, D02, D03, D07, or D08 peptides at room temperature for 2 h before incubated with A549 cells. After 1 h at 37 °C, fresh human PBMC were added and the rest of procedures were followed as described in (a). Experiments were carried out in triplicate, and the averages are shown. *P < 0·05, ***P < 0·001.