In rainbow trout spleen, il-4/13a (molecular marker of Th2 response) and il-8 downregulation were significantly positively correlated with the infection severity (Ct value in gill of Ich iag52a), indicating that the unpredictable repeated stress protocol impacted the rainbow trout ability to address a normal (i.e., infected fish group) immune response. This evidence concerns the gene COL4A2 and infection.