Any process involved in the development or functioning of the immune system, an organismal system for calibrated responses to potential internal or invasive threats
Note that this term is a direct child of 'biological_process ; GO:0008150' because some immune system processes are types of cellular process (GO:0009987), whereas others are types of multicellular organism process (GO:0032501).
1.GO REF: 0000022 2.GOC: add 3.Wikipedia: Immune system
is an element of the parent element
is a part of the parent element
is related to the parent element
derives from the parent element
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