The role of endotoxin for reactions after exposure to cotton dust.

Gram-negative bacteria and their endotoxins are present on all parts of the cotton plant and occur in large numbers after rain or frost. Endotoxins activate pulmonary macrophages that in turn recruit neutrophils into the airways. Platelets accumulate in pulmonary capillaries. The presence of these cells allows for the initiation of acute and chronic inflammation. Dose-response relationships have been demonstrated between endotoxin and fever, chest tightness, and reduction in air flow (bronchoconstriction) in cotton workers. Limited data suggest that after cotton dust exposure, other symptoms, such as airway hyperreactivity and chronic inflammation, are also related to the endotoxin exposure. Tentative thresholds for airborne endotoxins are presented.