Development and analysis of various clonal alloantigen-dependent cytotoxic cell lines from channel catfish

To determine the phenotypes of cytotoxic cells in channel catfish, clonal alloantigen-dependent leukocyte lines were established from mixed leukocyte cultures. Each clone was analyzed for expression of TCR alpha and beta genes by RT-PCR and for target cell specificity by Cr-51-release assay. Based on the above criteria, the following five different cell types were identified among the 19 clones analyzed: 1) TCR alpha beta(+) allospecific cytotoxic cells, 2) TCR alpha beta(+) nonspecific cytotoxic cells, 3) allospecific TCR alpha beta(+) noncytotoxic cells, 4) TCR alpha beta(-) nonspecific cytotoxic cells, and 5) TCR alpha beta(-) allospecific cytotoxic cells. The demonstration of cloned, TCR alpha beta(+), allospecific cytotoxic effecters provides the strongest evidence to date for the existence of cytotoxic T cells in fish.