— The Immune System (IS) constitutes the defence mechanism of higher level organisms to micro organismic threats: it is a real distributed system providing mechanisms of adaptation to unknown threats through the cooperation of heterogenous entities, and learning capabilities. This paper describes how the Situated Cellular Agents (SCA) model was applied to model the IS. After a brief description of the composing parts and internal mechanisms of the IS, the SCA model will be introduced and exploited to represent them1 .