Rainbow trout neutrophils are responsible for non-specific cytotoxicity

This is the first report that rainbow trout (Oncorhynchus mykiss) neutrophils are responsible for non-specific cytotoxicity. A monoclonal antibody (mab) for rainbow trout leucocytes was produced. Using this mab (TTL-5E9), neutrophils (5E9-positive cells) were isolated from the pronephros by a panning technique. The isolated neutrophils showed high viability (∼95%) and purity (92–95%), and were functional in cytotoxic activity assays. The neutrophils demonstrated significantly higher cytotoxic activities against YAC-1 target cells than the other cells (5E9-negative cells, predominantly lymphocytes). The number of neutrophils contaminating the 5E9-negative fraction and their non-specific cytotoxicities were positively correlated. These findings demonstrate that rainbow trout neutrophils possess non-specific cytotoxic activities.