Identification and characterization of clonal NK-like cells from channel catfish (Ictalurus punctatus)

Abstract TcR α, β, and γ chain negative cytotoxic NK-like cells were cloned from alloantigen-stimulated PBL obtained from naive channel catfish. Stimulation with allogeneic cells and growth promoting factors are required for their continued in vitro proliferation and cytotoxic activity. These granular cells kill not only the stimulating allogeneic cells, but also unrelated allogeneic targets by a perforin/granzyme-mediated apoptosis pathway. In addition, they are negative for markers that define neutrophils, monocytes/macrophages, and non-specific cytotoxic cells. Although these NK-like clones kill a number of different allogeneic targets, they display interclonal variation in cytotoxicity toward a panel of allogeneic targets, i.e. some clones have no apparent target specificity, while others display a target preference. In addition, flow cytometric analyses revealed that expression of a putative FcμR, an LFA-1-like molecule, and a putative thymocyte/T cell antigen varies among the different clones, with no clear correlation between surface antigen expression and cytotoxic activity. Although not all clones express a putative FcμR, it was noted that they all expressed an ITAM containing FceR γ chain homolog. This finding suggests that the catfish FceR γ chain may potentially be used as an accessory molecule for not only FcμRs, but also for other unknown activation receptors. These results support the hypothesis that catfish NK-like cells are heterogeneous in terms of target specificities and cell surface phenotype.