Dynamical and critical behavior of a simple discrete model of the cellular immune system

A simple cellular automata model has been constructed to investigate the interactions between the two T-helper subset cell types (TH1 and TH2) in a lymph node during chronic parasitic infection. The model exhibits behavior similar to a phase transition as a function of the antigenic burden placed on the host. At low antigen density the behavior of the model resembles that of a ''paramagnetic'' phase in which both T-helper cell subset cells can coexist. Above a threshold antigen density then one or other of the TH subset cells becomes dominant and forms a single, connected, infinite cluster (equivalent to a ''ferromagnetic'' phase). Much of the phenomenological behavior of the model is seen to be in good agreement with that observed in animal models of parasitic infection. © 1994 The American Physical Society.