The Immune System And Their Role Of The Immune System

The immune system is a highly evolved and complex defence system, armed against millions of potential pathogens that may cause infection at any point. Pattern recognition receptors, known as PRRs, are displayed by the cells of the innate immune system, such as macrophages and dendritic cells, and recognise pathogen associated molecular patterns or PAMPs. PAMPs are evolutionary conserved structural similarities found in many pathogens but not in the host’s own cells allowing the innate immune system to distinguish between self and non self and to react to the pathogens immediately (Mogensen, 2009). Antigen recognition receptors are used by the lymphocytes of the adaptive immune system to provide a highly specific and targeted response to a precise epitope of an antigen. However as a single lymphocyte carries only a single type of antigen recognition receptor that recognises one type of antigen the chance of a pathogen of finding a lymphocyte with a given specificity is low. Therefore the adaptive immune response takes time to mobilise hence the innate immune system is essential to keep the infection

The less specific nature of PRRs is crucial to the immediate role of the innate immune system allowing them to respond to a wide range of pathogens. In line with their role innate immune cells are found dispersed throughout the body (Mogensen, 2009). In contrast T and B cells will congregate in the lymph nodes until they are activated. As I previously mentioned finding a T or B cell with a specific antigen binding capability is rare so therefore once a precise lymphocyte has been activated by an antigen, it must undergo clonal expansion to ensure there is sufficient amount of that specific cell to neutralise the pathogen and this process takes a few days. Therefore numbers and effectiveness of specific TCRs and BCRs fluctuate with time (Kindt, et al.,