Constitutive and LPS-induced gene expression in a macrophage-like cell line from the rainbow trout (Oncorhynchus mykiss).

The lack of cell lines from mononuclear phagocytes of salmonid fish has impeded the study of immune function at a cellular level in these economically and ecologically important animals. Here, we report on the further characterization of RTS11, a previously described macrophage-like cell line from the rainbow trout spleen, with regard to its expression of a number of immunologically relevant genes. Analysis of gene expression by reverse transcription-polymerase chain reaction, using rainbow-trout-specific primers demonstrated that RTS11 cells express the beta chain of the class II major histocompatibility complex, the cytokines transforming growth factor-beta (TGF-beta) and interleukin-1beta (IL-1beta), and cyclo-oxygenase-2 (COX-2). Inducing the cells with lipopolysaccharide led to increased expression of IL-1beta and COX-2, as determined by Northern blotting. These results together suggest that RTS11 retains many of the characteristics expected of mature macrophages, and should be a valuable tool for further study of the expression and function of these immunomodulatory proteins in fish.