In the framework of interaction nets [6], Yves Lafont has proved [8] that every interaction system can be simulated by a system composed of 3 symbols named γ, δ and ε. One may wonder if it is possible to find a similar universal system with less symbols. In this paper, we show a way to simulate every interaction system with a specific interaction system constituted of only 2 symbols. By transitivity, we prove that we can find a universal interaction system with only 2 agents. Moreover, we show how to find such a system where agents have no more than 3 auxiliary ports.