The vertebrate immune system is an extremely complex adaptive system, consisting of around 1012 cells of 20 species. Like the circulatory system, the immune system has its own specialized organs and a system of vessels to allow cells to move through the body. Unlike the circulatory system, the immune system learns over time. Specifically, the Immune system can learn the chemical signature of a specific pathogen and produce cells targeted towards that particular pathogen.
Modeling this system is very difficult. The large number of different cells and the huge number of possible mutations and pathogens creates a fairly daunting scenario. However, a number of different research groups have been working on this problem for many years. There are several sophisticated immune system simulators. The largest family of such simulators appears to be the ImmSim group, based on the work of Sieden and Celada.
C-ImmSim, an adaptation of ImmSim available from Fillipo Castiliogne available under a GNU Public license. You can download it from here or from the author.
