In vitro alternative and classical activation of complement by extracts of cotton mill dust: a possible mechanism in the pathogenesis of byssinosis.

Extracts of cotton mill dust (CDE) were shown to activate complement by the classical and alternative pathways. Activation of the classical pathway, presented in this study for the first time, was verified by C1 consumption, C2 destruction, and C4 conversion tests. The component of cotton dust that causes complement activation precipitated in the presence of 20% saturated ammonium sulfate. The data presented suggest that endotoxin is not the principal complement-activating component, as complement activation could not be correlated to endotoxin concentrations of extracts of various parts of the cotton plant. Proteolytic enzymes were also eliminated as possible causative agents of complement cleavage since CDE did not cleave purified C3 in the absence of other complement components. Polyvinylpolypyrrolidone failed to remove the complement-activating component in CDE demonstrating that polyphenolic tannins are not the causative agents. Involvement of complement activation in the pathogenesis of byssinosis could explain in part the mechanism and symptoms of the acute byssinotic reaction.