After co-infection (Ctrl + PRRSV-2/H3N2), TNF, IFN-γ, IL-12p40, IL-4 and CXCL-13 transcripts were all up-regulated (mean fold change of 2.43, 1.86, 3.47, 2.49 and 2.83, respectively). This evidence concerns the gene CXCL13 and coinfection.