Our immune system constantly interacts with our internal environment, protects us from our external environment and provides the inherent knowledge to sense the difference between friend and foe with important implications in human health and disease (Pozo, 2008). For these reasons, it is important to identify functional alteration of key immune responses as the number of silver nano-enabled products grows while the current data strongly suggest that other related nanomaterials, such as polymer nanoparticles, fullerenes, dendrimers and gold nanoparticles, interact with the immune system.
In the present chapter, we will focus on the effects of engineered silver nanoparticles on the initiation and regulation of the immune response. Particular attention will be paid on the potential clinical usefulness of silver nanoparticles in the context of its effects on the production of key immunological mediators, as well as its significance on bacterial and viral infections. By a critical analysis of the current state of knowledge, the chapter will help to reduce the serious lack of information and controversial issues concerning the biological effects of silver nanoparticles on the immune system.
The Immune System
Studies on the biological consequences of new nanomaterials suited for biomedical applications are of importance, particularly those related to the immune system. Therefore, the interactions of silver nanoparticles with the immune system and its potential effects and implications are key questions for nanomaterials that are intended for biomedical applications or extensive industrial manufacturing such as those considered in this chapter. For this reason, before explaining the variety of interactions, effects and implications, we will start with a brief introduction about the functions of the immune system and its cellular components. The immune system is a dynamic network of cells, tissues, and organs that work coordinated to defend the body against attacks by “foreign” invaders and protects against disease by identifying “self” and “non-self” (for example virus, fungus, bacterium) cells and tissues (Christensen & Thomsen, 2009). To deal with antigens, the system uses specialized cells to recognize infiltrators and eliminate them. Detection is complicated as pathogens can evolve rapidly, producing adaptations that avoid the immune system and allow the pathogens to successfully infect their hosts (Christensen & Thomsen, 2009). For cellular communication there is a category of signaling molecules called cytokines. They are small secreted proteins which are critical to the development and functioning of both the innate and adaptive immune response, although they are not limited just to the immune system. They act by binding to specific membrane receptors, which produce cascades of intracellular signalling to alter cell functions.