[Immunology] The immune system

The mononuclear phagocyte system (also called the Reticuloendothlial system)

This system consists of an army of monocytes and the tissues which house them. Monocytes are immune cells which can travel around the circulatory system and settle in various tissues around the body. Once they have found an infection or damaged tissue they can differentiate into macrophages or myeloid dendritic cells.

Macrophages can recognise basic molecular signatures of debris and infectious agents. Their function is to phagocytose (eat) these threats and destroy them internally.

Dendritic cells ingest antigens (molecular signatures) and display them on their external appendages to passing immune cells. Their main function is to spread information about a potential infection.

 

The lymphatic system

This system consists of an army of lymphocytes, the tissues which store them (e.g. lymph nodes), and the vessels through which they travel (lymphatic vessels). It monitors for potential infections or cellular dysfunctions (e.g. cancerous cells) by recognising specific antigens which are unique to each threat. Once an antigen is recognised, the cells which are best at recognising that specific antigen are expanded into a large population to hunt down the threat.

Some immune cells can produce immunoglobulins (antibodies), which are proteins which circulate the body until they bind to their specific antigen. Antibodies are able to immobilise threats and help immune cells to identify them.