Functional comparison of avian heterophils with human and canine neutrophils

Phagocytosis, intracellular calcium flux, oxidant production and bactericidal activity of chicken heterophils and human and canine neutrophils were compared to assess their functional capabilities with respect to resistance of bacterial infection. Five strains of Staphylococcus were compared for bactericidal susceptiblity; two pathogenic strains isolated from chickens with tenosynovitis, a non-pathogenic strain from the tibiotarsal joint of a normal chicken, a pathogenic strain from the femoral joint of a human and a decapsulated derivative of the human strain. As assayed by flow cytometry, latex spheres were phagocytosed by significantly fewer chicken heterophils than by human or canine neutrophis. Phagocytes from all three species responded to stimulation by autologus serum-opsonised zymosan (aOZ) with an intracellular calcium flux, whereas only human neutrophils responded to N-formyl-methionyl-leucyl-phenylalanine (FMLP). None responded to phorbol myristate acetate (PMA). Neutrophils stimulated with aOZ and PMA produced significantly more H2O2 than did heterophils. Human neutrophils produced significantly greater H2O2 than did either canine neutrophils or chicken heterophils in response to FMLP. Greater bactericidal activity was observed against the decapsulated human strain and the non-pathogenic avian strain; this increased killing was found to be significant with the canine and avian cells. Avian heterophils were less phagocytic and produced less oxidant in response to zymosan than canine and human neutrophils. In addition, heterophils did not respond to PMA or FMLP.