The Neutrophil Response to Polyvinyl Sponge Implantation

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Abstract
Neutrophil release and migration in mice were studied over a 24-h period after the s.c. implantation of a single polyvinyl sponge. The release of neutrophils from the marrow was evaluated by directly counting the residual neutrophils in the femoral marrow of animals with sponges. Sponge and tissue neutrophil content was determined by extraction and assay of myeloperoxidase (MPO), a marker enzyme for neutrophils. A maximum depletion of 48% of the mature neutrophils in the marrow was observed 5 h after sponge implantation, in keeping with significant release of neutrophils for migration to the sponge. The released cells were not found in the circulating granulocyte pool, since neutropenia was noted. The accumulation of neutrophils in the sponge increased throughout the 24-h period, whereas in the tissue adjacent to the sponge maximum accumulation of neutrophils occurred within 7 h. In fact, neutrophils migrated to at least 3 sites-the sponge, the skin overlying the sponge, and the skin in which an incision had been made to insert the sponge. The sponge content of neutrophils represented 0.3-33% of the neutrophils migrating to the combined lesion (sponge and skin sites). If the neutrophil response to foreign body implantation is to be measured in its entirety, it is necessary to quantify not only the neutrophils within the foreign body but also those in the tissues surrounding it. The studies describe an animal model for neutrophil release and migration to tissues following a standard stimulus. This model may be useful in exploring the factors which influence the release and migration of neutrophils in vivo.