Immune system

system which forms antibodies and works against foreign bodies that attack the body

An immune system is a collection of mechanisms within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own healthy cells and tissues in order to function properly. Detection is complicated as pathogens adapt and evolve new ways to successfully infect the host organism.
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Immune system n. The integrated body system of organs, tissues, cells, and cell products that differentiates self from nonself and neutralizes [more]Immune system - Community and Resources

Noun
1. a system (including the thymus and bone marrow and lymphoid tissues) that protects the body from foreign substances and pathogenic organisms by producing the immune response
(hypernym) system
(part-meronym) marrow, bone marrow

A complex system that is responsible for distinguishing us from everything foreign to us and for protecting us against infections and foreign substances.