Phagocytosis and killing of Staphylococcus aureus by bovine neutrophils after priming by tumor necrosis factor-alpha and the des-arginine derivative of C5a

Objectives--To evaluate effects of proinflammatory mediators on phagocytosi s and killing of Staphylococcus aureus, the oxidative burst (OB), and expre ssion of receptors for opsonins by bovine neutrophils. Sample Population-Neutrophils from 10 cattle. Procedure-Neutrophils were primed with recombinant bovine tumor necrosis fa ctor-alpha (TNF-alpha) or the des-arginine derivative of bovine C5a (C5a(de sArg)) and mixed with S aureus. Phagocytosis and OB were measured by use of flow cytometry. Rate of phagocytosis and intracellular killing were evalua ted. Expression of receptors for immunoglobulins and the C3bi fragment of c omplement were estimated by use of flow cytometry. Results--Priming of neutrophils by TNF-alpha improved phagocytosis of S aur eus with a concentration-dependent effect. Phagocytosis of preopsonized was hed bacteria was increased by activation of neutrophils with C5a(desArg). P hagocytosis was optimal when neutrophils primed with TNF-alpha were activat ed with C5a(desArg). The OB of phagocytizing neutrophils was highest when T NF-alpha and C5a(desArg) were used in combination. Bactericidal activity of neutrophils was stimulated by priming with TNF-alpha or C5a(desArg). Bindi ng of bovine IgM or IgG(2) to bovine neutrophils was not stimulated by TNF- alpha, C5a(desArg), or both, and aggregated IgG1 did not bind to neutrophil s regardless of their activation state. Both TNF-alpha and C5a(desArg) incr eased expression of beta 2 integrins (CD18), with the highest expression wh en they were used in combination. Conclusions and Clinical Relevance--The mediators TNF-alpha and C5a(desArg) stimulated phagocytic killing by neutrophils and potentiated each other wh en used at suboptimal concentrations. Bovine neutrophils have enhanced bact ericidal activities at inflammatory sites when TNF-alpha, C5a(desArg), Or b oth are produced locally.