The Immune System (IS) represents the defence mechanism of higher level organisms to micro organismic threats. It is a genuinely distributed system provided with mechanisms of adaptation to unknown threats by means of the cooperation of heterogenous autonomous entities. Features of the overall systems, such as learning capabilities, possibility to tackle unknown threats in any part of the body, are a consequence of these interactions. This paper describes how a Multi-Agent approach, and more precisely the Situated Cellular Agents (SCA) model, can be suitably applied to represent specific elements and mechanisms of the IS. After a brief description of the composing parts and the internal mechanisms of the IS, the SCA model will be introduced and exploited to represent them(1).