Almost all the higher organisms have well developed mechanisms for defending against the microorganisms. Innate and adaptive system work together as they are the components of host integrated system. However there are many microbes that have developed and adapted to resist the innate immunity and hence more robust mechanisms are required for their expulsion. Innate and adaptive immune systems are interlinked; stimulation of anyone against the foreign substances instigates the other and hence functions cooperatively.

 

Table 1.1 common features of innate and adaptive immunity:

The mechanism of innate immunity provides an initial defense against the infection. Adaptive immune responses develop later and consist of lymphocytes.