IL1B and infection: In HD11 cells, spleens and bursae, infection with vvIBDV strain UPM0081 induced increased mRNA expression levels, in a dose-dependent manner, of pro-inflammatory cytokines and chemokines, Th1 cytokines, iNOS and MHC class I. This result is similar as previously reported [24,25] where IBDV infection promoted upregulation of proinflammatory cytokines including IL-1β, IL-6, IL-18 and iNOS of adherent putative macrophage cell isolated from bursae of IBDV challenged chicken.