Immunology

Immunology is the study of the immune system. The immune system is the parts of the body which work against infection and parasitism by other living things. Immunology deals with the working of the immune system in health and diseases, and with malfunctions of the immune system.

An immune system is present in all plants and animals. We know this because biologists have found genes coding for toll-like receptors in many different metazoans.^[1] These toll-like receptors can recognise bacteria as 'foreign', and are the starting-point for immune reactions. The type of immunity which is triggered by the toll-like receptors is called innate immunity. This is because it is entirely inherited in our genome, and is fully working as soon as our tissues and organs are properly developed.

Vertebrates, and only vertebrates, have a second type of immunity. This is called adaptive immunity, because it 'remembers' previous infections. Then, if the same infection occurs again, the reaction is much stronger and faster. This immunological memory "confers a tremendous survival advantage" and with it vertebrates "can survive over a long lifetime in a pathogen-filled environment".^[1]

1. ↑ ^{1.0 1.1} Janeway, Charles A. 2001. Evolution of the imune system: past, present and future. In Janeway C.A; Travers P; Walport M. & Shlomchik M. 2011. Immunobiology: the immune system in health and disease. 5th ed, Garland, New York. 597–611 ISBN 0-8153-3642-X