Integrated Innate Immunity—Combining Activation and Effector Functions

The previous sections have provided an overview of the main functional components, the response systems, and the effector mechanisms of the innate immune system. This has included, amongst others, the immune cells, the complement system, inflammatory mediators, pattern recognition receptors, cell death, cytokines, and chemokines. These elements were previously introduced in isolation. However, the innate response to infection, damage, or danger does not occur in an isolated manner. Many immune stimuli will activate a variety of different response pathways and induce the activation of a multitude of effector functions. In this section, I will look in more depth at some of the key mechanisms that combine the activation of the immune response and the induction of effector molecules to clear the danger and initiate resolution and the restoration of homeostatic balance. The primary focus will be upon pathways involving pattern recognition processes as because these are both fundamental and integral to the whole innate immune response. In particular I will describe the extracellular and intracellular detection of lipopolysaccharide, the production of IL-1β following activation of the inflammasome, and the responses to infection with the bacterium Salmonella and the virus Influenza A.