T cell responses in PBMCs isolated from pigs after PRRSV infection. PBMCs were separated at the indicated days, immunostained with the appropriate antibodies, and 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; **p < 0.001). *nt: not tested because of sample shortage.