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In vitro and in vivo changes in human complement caused by silage.

Olenchock SA; May JJ; Pratt DS; Lewis DM; Mull JC; Stallones L
Environ Health Perspect 1986; 66:91-96
A study was conducted to determine the effects of silage extracts on human complement activation in-vitro, and to report the in-vivo changes in complement components C3 and C4 in farmers exposed to airborne silage dust. An acute, febrile illness of short duration has recently been identified in farmers unloading the contents of silos, and it has been theorized that complement activation may play a role as the initiator or contributor to this syndrome. Extracts of four silage samples known to have caused adverse reactions in humans were prepared and tested against normal human serum in-vitro. The endotoxin concentration of each extract was also determined. Each extract was shown to consume complement component C3 in a dose dependent fashion. However, the most active silage extract also had the highest level of endotoxin contamination. Chelation of the serum to block the classical pathway indicated that the alternate pathway of complement activation was involved. Serum C3 and C4 levels were measured in nine farmers prior to exposure to silage dust. Under actual working conditions, these individuals were exposed to silage dusts. Three of the nine became ill subsequent to exposure. C4 and C3 levels were measured in all individuals 6 hours after exposure. Mean serum C3 levels were decreased in both the exposed farmers and those who became ill, but the difference was not statistically significant. Mean serum C4 was significantly lower than comparisons (wives of farmers) in the three farmers who became ill. Sera from each of the study groups was tested for immunoglobulin-E, and none of the exposed or ill farmers was positive for specific antibody to the antigens to which they were exposed. The authors conclude that aqueous extracts of silage can activate complement in-vitro, and that in-vivo changes may also occur.
NIOSH-Author; In-vitro-studies; Occupational-exposure; Vegetable-dusts; Hemoproteins; Immunological-tests; Pulmonary-system-disorders; Airborne-particles; Agricultural-workers; In-vivo-studies
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Environmental Health Perspectives
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division