Characterization of endotoxin-induced C5-derived chemotactic activity in aqueous humor

J. T. Rosenbaum, K. Wong, H. D. Perez, W. Raymond, E. L. Howes

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18 Scopus citations

Abstract

Although a cellular exudate characterizes acute anterior uveitis, few studies have sought to identify the chemoattractant(s) contributing to this phenomenon. As a model of acute ocular inflammation, the authors have injected rabbits intravenously with endotoxin (Salmonella typhimurium LPS, 2.5 μg/kg). In a Boyden chamber assay, aqueous humor drawn 3 hr after LPS (post-LPSaqueous) exhibited chemotactic activity for purified rabbit granulocytes (PMN). 'Checkerboard' analysis indicated that chemotaxis, rather than protein-induced chemokinesis, primarily accounted for PMN migration. Aqueous from normal rabbits demonstrated no chemotactic activity. Chemotactic activity was maximal at 3 hr post-LPS (versus 1 or 5 hr). PMN migration exhibited a direct correlation with the concentration of aqueous tested (0.5-5%). Several observations indicated that this chemotactic activity is complement (C5)-derived. It is inhibited by antibodies to C5 but not affected by antibodies to C3. Similar to rabbit C5a, chemotactic activity in post-LPS aqueous was heat stable at 56°C x 30 min, attracted both human and rabbit PMN at similar concentrations and induced release of beta glucuronidase from PMN. In addition, prior incubation of rabbit PMN with partially purified C5a (desensitization) specifically inhibited chemotactic responses to both C5a and post-LPS aqueous without inhibiting responses to another chemoattractant, n-formyl-methionyl-leucyl-phenylalanine. Finally, chemotactic activity from post-LPS aqueous could be recovered from a Sephadex G75 column and eluted similarly to chemotactic activity in zymosan activated rabbit serum or 13,700 D molecular weight marker. The presence of complement-derived chemotactic activity in this model should not be construed as evidence that this activity contributes to the pathogenesis of endotoxin-induced inflammation. In fact, an endotoxin-induced neutropenia along with other factors may diminish the role of any chemotactic factor 3 hr after LPS. The ability, however, to detect and identify a specific chemotactic factor in a small volume of biologic fluid offers the potential that forms of uveitis can be characterized in terms of their associated chemotactic activity.

Original languageEnglish (US)
Pages (from-to)1184-1191
Number of pages8
JournalInvestigative Ophthalmology and Visual Science
Volume25
Issue number10
StatePublished - Nov 22 1984

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ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience

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