Chapter 6: Undesirable Adjuvanticity of Nanoparticles and Its Implication in Modulation of T Helper Responses

Although the adverse direct health effects of nanoparticles/materials have been proposed and are being clarified widely, their facilitating effects on preexisting pathological conditions have not been fully examined. In this review, I provide insights into the immunotoxicity of nanoparticles/materials as an aggravating factor in hypersusceptible subjects, especially those with immune-related respiratory disorders using our in vivo experimental model. I first exhibit the effects of nanoparticles/materials on lung inflammation induced by bacterial endotoxin (lipopolysaccharide: LPS) in vivo as a disease model in innate immunity, and demonstrated that nanoparticles instilled through both an intratracheal tube and an inhalation system can exacerbate the lung inflammation. Secondly, I introduce the effects of nanoparticles/materials on allergic asthma in vivo as a disease model in adaptive immunity, and showed that repetitive pulmonary exposure to nanoparticles has aggravating effects on allergic airway inflammation, including adjuvant effects on Th2-milieu. Taken together, nanoparticle/ material exposure may synergistically facilitate pathological inflammatory conditions via both innate and adaptive immunological abnormalities.