Independently of the individual variability, blood from NS-reassortant virus infected chickens clearly showed a lymphocyte reduction that correlated with an increase in the number of macrophage/monocyte-like cells that peaked at 48 h pi Interestingly, while no evident up-regulation of IFN-β was observed independently of the animal group and infection time (data not shown), a dramatic increase of IL-1β expression was found in both reassortant-infected groups at 48 h pi, being higher in those animals infected with FPV NS GD (23.6% cells expressing IL-1β) (Figure 4). The gene discussed is IL1B; the disease is infection.