Guinea pigs were exposed for 40 minutes to an aerosol of different endotoxins. Pure endotoxin (PE), endotoxin on cell walls (CE) and pure endotoxin bound to cellulose powder (PE+cp) was prepared from Enterobacter agglomerans and Pseudomonas syringae.

The increase in the number of free ling cell, particularly neutrophils, obtained in lung lavage at 24 hours after the exposure to CE was dose-related and similar for E. agglomerans and P.syringe. The neutrophil increase was higher after exposure to PE, whether this was in pure form or bound to cellulose powder. It is suggested to use CE as the agent when exposure challenges are used to evaluate the importance of endotoxins in organic dusts.