Vaccine design is now approached from a more rational, less pathogen-based perspective and, increasingly, immunology is guiding vaccine researchers towards new horizons with the potential to improve on nature. As such, the basic concepts of immunology are an essential component of the foundations of modern

vaccinology. To understand the immunology of vaccines, it is important first to examine the key players of the immune Selleck Ibrutinib system (Figure 2.2) and to understand how they are produced, activated and regulated. In the following section we will discuss the innate and adaptive phases of the immune response and how these are bridged by the actions of specialised antigen-presenting cells (APCs) – a key step in the successful response to vaccination. Physical and chemical barriers comprise the body’s first line of defence – including the skin, ciliated epithelia, mucous membranes, stomach acids and destructive enzymes in secretions. The immune system in vertebrates is a network of cells, tissues and organs that function in a coordinated fashion to defend the body against factors that could penetrate its physical and chemical barriers. Some of the key organs of the immune system are illustrated in Figure 2.3, and include the primary lymphoid organs (bone marrow and thymus) where lymphocytes are generated, and the

secondary lymphoid organs (peripheral lymph nodes, spleen, tonsils, Peyer’s patches) where immune responses are initiated and regulated. selleck inhibitor Although we

are continuously exposed to external antigens, foreign substances and microorganisms, under normal circumstances food and airborne antigens do not provoke the heptaminol immune system. In addition, some normal commensal floras have also co-evolved with their human hosts to suppress or avoid triggering defence mechanisms. It is now known that this is partly because immune responses are usually only triggered in the context of threat or damage to the host; however, both self and non-self-antigens have the potential to trigger immune responses under conditions of acute or chronic inflammation. All organisms have some form of innate protection against the outside world, which may be as simple as a cell wall or waxy coating. As higher organisms evolved, their innate defences became more sophisticated and the jawed vertebrates developed a highly specialised system of immunity – acquired (or adaptive) immunity – which may have evolved as a consequence of co-evolution with specialised parasites, increased metabolic rates due to dietary changes, and genomic instability. Jawed vertebrates thus have two interlinked systems which act sequentially to establish protective immunity – the innate immune system and the adaptive immune system. The innate immune system acts as a first line of defence which comprises both cellular and non-cellular effectors.