Frequencies of T lymphocyte subsets in PBMC and tissues of uninfected and infected pigs. Single-cell suspensions were immunostained to determine the frequency of various T-cell phenotypes in A PBMC, B lung parenchyma, C BAL and D BLN. Based on intracellular IFN-γ staining, the frequencies of Th1 cells (IFN-γ+ in CD4+CD8−) and CTL (IFN-γ+ in CD4−CD8+) were analysed. IL17 expression and its modulation was apparent in two types of cells: IL17-producing CD4+CD8− cells and IL17-producing CD4−CD8+ cells. Each bar represents the average percentage of immune cells ± SEM. The asterisks (*) indicate statistically significant differences between the averages found for the uninfected (NC) pigs and those found for the challenged pigs at each time point (* indicates p ≤ 0.05, ** indicates p ≤ 0.01 and *** indicates p ≤ 0.001).