Applications of Nanomaterials for Activation and Suppression of Immune Responses

Background

Nanomaterials could be from either natural or designed synthetic materials for specific targeting of particular tissues. Hence, it is important to investigate the interactions between materials and the immune system to understand their mode of action and the underlying cellular pathways. As we know that our immune system protects us from entry of pathogenic microbes or substances. Sometimes, immune cells recognize nanomaterials as foreign and thus multi-level immune responses might be generated against them causing toxic reactions (Nel et al., 2006) . For example, localized toxicity in the form of granuloma formation was observed in various organs of animals exposed to nanotubes (Poland et al., 2008). Therefore, materials that are recognized as self are important for the delivery of drug/antigen/genetic elements. It has been well established that chemical nature, size and charge of the nanomaterials could determine the compatibility with the immune system (Dobrovolskaia et al., 2008; Aggarwal et al., 2009). For example, coating of polyethylene glycol (PEG) over nanoparticles could potentially reduce the immune system recognition due to hydrophilic nature of PEG (Moghimi, 2002). However, anti-PEG antibodies were detected after the administration of PEG coated liposomes (Ishida et al., 2007) that could potentially increase the clearance of PEG coated nanoparticles from circulation (Ishida et al., 2006). Therefore, generation of particle-specific immune responses could reduce the therapeutic potential of the delivered biomolecules. On the other hand, nanomaterials could be engineered specifically either for the stimulation of antigen presenting cells (APCs) or for direct delivery of antigens to specific cells/tissues.