IRF7 and infection: However, upon infection with SE, we found a significant up-regulation in six other TLR signaling pathway genes in the heterophils from line A chickens: MD-2, TIRAP, IKKε, NF-κB2, p38 MAPK 11, and p38 MAPK 12 in addition to IRF7 when compared to line B heterophils (p < 0.01).