IL4 and infection: Although results can vary depending on the dose and virulence of the P. perurans, fish size, duration of infection and use of lesion or non-lesion specific gill tissue, these earlier studies found a localised immune suppression with genes involved in Th1, Th17 and Tregs pathways being down-regulated12, while pro-inflammatory cytokines (Il-1β)13,and Th2 cytokines (il4/13a and il4/13b2)12,14 were up-regulated.