immune system process biological_process GO:0002376 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). Any process involved in the development or functioning of the immune system, an organismal system for calibrated responses to potential internal or invasive threats. Wikipedia:Immune_system biological process biological_process biological phase