Innate cellular immune function of anterior kidney leucocytes in the gulf killifish,Fundulus grandis

Non-specific cell-mediated immune functions of the gulf killifish (Fundulus grandis) were characterised so that the potential of this fish as a model species in stress immunophysiology and pollution studies could be assessed. Leucocytes from the pronephros were separated over discontinuous Percoll gradients and identified based on differential staining characteristics. Two enriched fractions of cells were then examined for their ability to phagocytose zymosan orVibrio anguillarum, to produce the reactive oxygen intermediates (ROIs) superoxide and hydrogen peroxide, and their natural cytotoxic cell (NCC) activity against K562 and YAC-1 targets. The leucocyte population at the 1·040–1·060 g ml−1interface was comprised of macrophages, lymphocytes and eosinophilic granulocytes (EGCs), while the 1·060/1·080 g ml−1interface contained mostly EGCs. There were typically 10-fold fewer cells in the former fraction. Light and electron microscopy revealed that both macrophages and EGCs were able to ingest zymosan andV. anguillarum. Fractions containing these cells also produced ROIs in response to phagocytic stimuli, with the EGCs having activity levels several times greater than that of the macrophages. NCC activity was limited to the 1·040–1·060 fraction, and was evident only against YAC-1 targets, but not against K562 targets. These results indicate that this fish would be suitable as a biomedical model in studies of non-specific cellular immune function as it relates to immunophysiology and environmental quality.