Priming of cytokine release and increased levels of bactericidal permeability-increasing protein in the blood of animal facility workers

Objective: To investigate cellular immune responses in laboratory animal workers who are exposed to high levels of animal allergens but also to other biologically active substances containing lipopolysaccharides (LPS), i.e., endotoxins. Methods: A survey among 20 animal facility workers and 20 matched (gender, smoking) controls was conducted using exposure measurements (endotoxin, colony-forming units of bacteria and fungi) and a questionnaire on respiratory symptoms. Blood samples were taken to determine the ex vivo whole-blood release of tumor necrosis factor-alpha (TNF) and interleukin-8 (IL-8) as well as plasma levels of LPS-binding protein (LBP), bactericidal permeability-increasing protein (BPI), the 75-kDa soluble TNF receptor (sTNFR75), and total/specific IgE. Results: Although exposure to endotoxin was low (range 0.05–2.8 ng/m3), a significant (P < 0.05) increase in plasma BPI (4-fold) and srTNF75 (1.2-fold) was found, suggesting a response to inhalation of LPS. Also, the capacity of blood leukocytes to release TNF and IL-8 in response to ex vivo exposure to workplace dust was increased. Data were not confounded by specific allergies, levels of IgE, smoking, or respiratory symptoms. Conclusions: A profound effect on the cellular immune response was seen in animal workers with low endotoxin exposure and a high antigenic load. It remains to be determined which other biologically active substance(s) are involved in this effect.