In vitro responses of channel catfish, Ictalurus punctatus, neutrophils to Edwardsiella ictaluri

The in vitro responses of channel catfish peripheral blood neutrophils to Edwardsiella ictaluri were examined through the use of phagocytic, bactericidal, and chemiluminescent assays. Evidence from both light and electron microscopy indicate that catfish neutrophils appeared to phagocytose E. ictaluri. Although extracellular killing of E. ictaluri was observed, bactericidal assays did not demonstrate intracellular killing of E. ictaluri by neutrophils. Catfish neutrophils mount a chemiluminescent response to E. ictaluri which is enhanced by the presence of specific antibody. Incubation of catfish neutrophils with LPS from E. ictaluri appeared to suppress the chemiluminescent response to opsonized zymosan.