Fig. 6.

fAPN expression in feline macrophages treated with FIPV-infected macrophage culture supernatant. SPF cat-derived macrophages (2 × 10⁶ cells) were inoculated with a mixture of FIPV and α-FIPV S MAb. The culture supernatant was collected after 3 days, and heated at 56 °C for 30 min to inactivate viruses. SPF cat-derived macrophages (2 × 10⁶ cells) were cultured with medium containing 10% inactivated culture supernatant. The cells were collected on days 0, 1, 3, and 5 of culture, and the intracellular fAPN mRNA (A) and cell surface fAPN (B) expression levels were measured. fAPN mRNA was quantitatively analyzed in terms of the relative density value to the mRNA for the housekeeping gene GAPDH. White circle: Treatment with control macrophage culture supernatant, black circle: treatment with culture supernatant of macrophages inoculated with a mixture of FIPV and α-FIPV S MAb. n = 5, **p < 0.01 vs. treatment with culture supernatant of intact (control) macrophages.