The adherence of serum-opsonized yeast to neutrophils results in phagocytosis of these particulate stimuli and activation of the respiratory burst. Both events are mediated or modulated in part by the surface receptors for IgG and complement. The link between the binding of complex particulate stimuli to the cell surface, and the triggering of these neutrophil functions, is not completely understood. We have previously described an anti-human neutrophil, murine monoclonal antibody PMN7C3, which specifically inhibits the respiratory burst of neutrophils stimulated with serum-opsonized yeast. In the present study, we show that the antigen recognized by PMN7C3 (PMN7 antigen) is present on a number of neutrophil proteins, including the recently described group of related leukocyte membrane glycoproteins CR3, LFA-1, and p150,95. The PMN-7 antigen differs from other antigens associated with the C3bi receptor complex (MAC 1, MO 1, OKM1, OKM10) in that it is present only on neutrophils among peripheral blood cells. Furthermore, the binding of PMN7C3 to the neutrophil surface inhibits the activation of the respiratory burst by serum opsonized zymosan without affecting phagocytosis of these particulate stimuli. The cross-linking of cell surface PMN7 antigen by multivalent antibody is associated with the capping and internalization of antigen-antibody complexes, and appears to be necessary for the expression of maximum inhibition of opsonized zymosan-triggered respiratory burst activity. PMN7C3 also binds to a group of granule-associated proteins biochemically distinct from CR3, LFA-1, and p150,95. These granule-associated proteins containing PMN7 antigen can be mobilized to the cell surface with secretion. PMN7 antigen-bearing proteins may play a role in modulating the activation of the respiratory burst associated with phagocytosis of serum-opsonize zymosan.

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