THE IMMUNE SYSTEM
The immune system is an organisation of complex biological structures such as specialised tissues, cells, organs that coordinate the resistance and defence against disease. The immune system protects the body by defending against invading pathogens such as arthropods, viruses and worms. The overcoming of potential threat from disease is called immunity. In vertebrates, immunity can be either innate or acquired.
The body possesses a range of defence mechanisms to defend against invading pathogens. These mechanisms can be non-specific (innate), where an array of pathogens is targeted and specific (acquired/adaptive), where a specific pathogen is targeted. Non specific and specific defence systems can be categorised into three levels. These three levels are the first line of defence, the second line of defence and the third line of defence.
If the immune system does not function properly, diseases and disorders can develop. Such diseases include autoimmune diseases and immunodeficiency diseases.
An autoimmune disease is a condition where the cells of the immune system mistakenly attack cells and tissue belonging to its own body. The immune system fails to recognise protein molecules or MHC markers belonging to tissue and cells of the same body and identifying them as belonging to the body. The treatment for autoimmune diseases is the use of immunosuppression drugs which suppress the immune system to decrease immune response and therefore reduce the effects of the autoimmune disease however adverse affects are also experienced as decreased immune function increases susceptibility to diseases.
Immunodeficiency diseases occur when the immune system’s ability to defend the body against disease is hindered or non existent. These diseases may be genetic or acquired. The failure to respond to invading pathogens results in the development of opportunistic diseases.