ABSTRACT
This chapter examines the ways in which various classes of pathogen attempt to evade the host immune system and focus on common themes employed by them and deals with evasion of innate immunity. Traditionally the human immune system has been considered to comprise two parts, the innate immune system and the adaptive immune system. In comparison, the adaptive immune system evolved in jawed fish. The adaptive immune system is slow in onset but highly specific in its response and exhibits memory in that it responds more rapidly and with greater magnitude and specificity to a second and subsequent exposures/encounters with the same agent. The secretion or liberation of cell wall or cell membrane molecules by pathogens can consume immune factors such as complement components and antibodies so that they are unavailable to bind to targets on the surface of the pathogen.
