IL-10, IFN-纬 and GM-CSF mRNA expression was upregulated in a dose-dependent manner for all age groups (P < 0.05). Age-related differences included a significantly increased IL-10 mRNA and protein production in newborn piglets compared to post-weaned and young pigs. IL-10 production pattern was similar with a higher peak between 12 and 36 h post-induction in all age groups. In contrast, IFN-纬 mRNA and protein level was significantly elevated in young pigs 12 h and 24 h post-induction, respectively, while the time course production of IFN-纬 was mostly consistent in newborn and post-weaned piglets. GM-CSF mRNA expression was significantly lower in newborn piglets than in post-weaned and young pigs. The kinetic of GM-CSF expression peaked at 12 h in young and post-weaned pigs and at 24 h in newborn piglets. IL-4 mRNA levels were very low and no apparent change of IL-2 expression was observed following LPS stimulation in all age groups. Only very low levels of NO were detected in the cell supernatants of young pigs. Collectively, these studies suggest age-related differences in time-dependent production of IL-10, IFN-纬 and GM-CSF by porcine AMs with potential immunoregulatory consequences to be explored further.