T cell responses in lungs and BALc collected from pigs after PRRSV infection. Mononuclear cells isolated from the lungs (A) and BALc (B) were immunostained with the appropriate antibodies on the indicated days and then analysed by flow cytometry to detect gamma-delta (γδ) T cells (γδT), type 1 helper T cells (Th1), T helper 17 cells (Th17), cytotoxic T lymphocytes (CTLs) and regulatory T cells (Tregs). The error bars represent the SEM. Asterisks indicate significant differences in T cell proliferation among the genotypes (*p < 0.05). *nt: not tested because of sample shortage.