Neutrophil activation on biological surfaces. Massive secretion of hydrogen peroxide in response to products of macrophages and lymphocytes.
Academic Article
Overview
abstract
Recombinant tumor necrosis factor alpha (rTNF alpha) and beta (rTNF beta) did not trigger H2O2 release from PMN in suspension. However, when PMN were plated on polystyrene surfaces coated with serum, fibronectin, vitronectin, laminin, or human umbilical vein endothelial cells (HUVEC), rTNFs induced a massive, prolonged secretory response, similar to that elicited by phorbol myristate acetate (PMA) or bacteria. On serum-coated plates, the maximum sustained rate of H2O2 release in response to rTNF alpha was 2.6 +/- 0.2 nmol/min per 10(6) PMN, the same as that with PMA; release continued for 73 +/- 4 min. On laminin-coated surfaces or HUVEC, release of H2O2 in response to rTNFs was slower, but lasted approximately 3.5 h, reaching the same total (greater than 100 nmol/10(6) PMN). Not only was this response far longer and larger than for other soluble stimuli of the respiratory burst studied with PMN in suspension, but the concentration necessary to elicit a half-maximal response (EC50) for rTNF alpha was orders of magnitude lower (55 pM). Responses were similar with FMLP, but ranged from zero to small with recombinant IFN alpha, recombinant IFN beta, recombinant IFN gamma, platelet-derived growth factor, recombinant IL-1 beta, or bacterial lipopolysaccharide. Adherent monocytes did not secrete H2O2 in response to rTNFs. H2O2 secretion by adherent PMN was first detectable 15-90 min after addition of rTNFs or FMLP. This lag period was unaffected by prior exposure of PMN to rTNF alpha in suspension, by allowing PMN to adhere before adding rTNF alpha, or by incubating adherent PMN in medium conditioned by rTNF alpha-treated PMN. Cytochalasins abolished H2O2 secretion in response to rTNFs, but not FMLP, if added during, but not after, the lag period. Thus, H2O2 secretion from rTNF alpha-treated PMN appears to be a direct but delayed response that requires assembly of microfilaments during exposure to the cytokine. These results suggest that PMN adherent to intra- or extravascular surfaces may undergo a massive, prolonged respiratory burst at the command of macrophages and lymphocytes reacting to microbial products and antigens.
