10 - The innate defences of the body

Abstract

The immune system has a challenge. It needs to defend us against pathogens that range in size from the smallest viruses to the large helminth worms. These pathogens may also infect us by different routes, including by aerosol, by ingestion, through the skin, or through sexual contact. In the preceding chapters, we have outlined some of the fundamental characteristics of the many types of microparasites and macroparasites (here collectively called pathogens) that may infect the body. We now turn to consider the ways in which the body seeks to defend itself against infection by these organisms, starting with the innate immune responses that are the first line of defence.