Fig. 3

Antiviral T cell proliferative responses during primary FIPV infection. Representative FACS plots comparing unstimulated to WKV and viral peptide stimulation in CD3 + CD4+ T cells are shown (a). PBMC were assessed for viability by live/dead exclusion and interrogated by staining for CD3, CD4 or CD8 as described in Methods. T cell subsets were then assayed for proliferation responses to different viral immunogens based on positive staining for BrdU using an anti-BrdU monoclonal antibody. A comparison of the frequencies of CD4 and CD8 cells showing proliferation after stimulation with WKV or FIPV peptide stimulation is shown for rapid progressors, slow progressors and survivors (FIP resistant cats) before and after FIPV inoculation (b). Horizontal lines represent median values for each group. Significant differences were not detected for T cell frequencies between different disease outcomes at each time point based on a pair-wise analysis by one-tailed Mann-Whitney U test