To elucidate the pathogenesis of H1N1pdm in pigs, we examined the pattern of cytokine responses in pH1N1-infected swine macrophages. Total RNA from infected and uninfected 3D/ 4 cells collected at different time points post infection (p.i.) were prepared and used for realtime RT-PCR analyses with specific primers to swine cytokines. We found that the levels of proinflammatory cytokines IL-6 and IL-8 were upregulated up to 51-and 38-fold at 16 hrs, respectively, and the level of IL-8 continued to rise up to 142-fold at 36 hrs p.i.. However, the level of IL-1b remained unchanged throughout the infection ( Fig. 2A) , indicating that IL-6 and IL-8, as well as TNF-a (Fig. 2B ) as described later, were the main proinflammatory cytokines upregulated.