Killing of Staphylococcus aureus by tumor necrosis factor-α-activated neutrophils: The role of serum opsonins, integrin receptors, respiratory burst, and degranulation

We have examined the effects of TNF priming on the killing of Staphylococcus aureus by human neutrophils. In the absence of serum opsonins, neutrophils failed to kill S. aureus, and TNF priming did not induce the cells to become bactericidal. Normal human serum, containing complement activity, promoted the killing of the bacteria by neutrophils. Pretreatment of neutrophils for 30 min with TNF significantly enhanced their bactericidal activity. The effects of TNF on neutrophil bactericidal activity was dependent on serum concentration and the degree of enhancement induced increased up to a concentration of 1%. The kinetics of bacterial killing showed that TNF-only enhanced the initial rate of killing, over the first 30 min. Little killing of bacteria occurred in the presence of complement- inactivated serum, and TNF did not stimulate this killing. These results suggest that TNF enhances the neutrophil complement-dependent killing of S. aureus. TNF increased the expression of CR3 (CD11b/CD18) and CR4 (P150, 95; CD11c/CD18) adhesion receptors but not LFA-1 (CD11a/CD18); and mAb against the α-chain of either CR3 or CR4 but not LFA-1 prevented the enhancing effects of TNF on the neutrophil bactericidal activity.