Release of leukotriene B₄ from human neutrophils after interaction with nontypeable Haemophilus influenzae

Opsonization of nontypeable Haemophilus influenzae with antibody is critical for the interaction between the organism and human polymorphonuclear leukocytes (PMNs). Nontypeable H. influenzae opsonized in fresh antibody-positive serum induced the release of 42.5 ± 17.9 ng of leukotriene B₄ per ml from PMNs after 20 min of incubation at 37°C. On the other hand, opsonization of the organisms in fresh antibody-negative serum stimulated the release of significantly smaller amounts of leukotriene B₄ by the PMNs. Simultaneous determinations of phagocytosis demonstrated similar patterns of response. A small amount (26.7 ± 7.6%) of unopsonized nontypeable H. influenzae was phagocytosed by PMNs during 20 min of incubation at 37°C. In contrast, 89.3 ± 2.0% of nontypeable H. influenzae opsonized in fresh antibody-positive serum was phagocytosed during the same incubation period (P < 0.001). Removal of complement through heat inactivation at 56°C for 30 min did not significantly affect phagocytosis. These data suggest that the humoral immune response to nontypeable H. influenzae plays an important role in the inflammatory process and may contribute to the production of middle ear effusions in otitis media.