DYNAMICAL AND CRITICAL-BEHAVIOR OF A SIMPLE DISCRETE MODEL OF THE CELLULAR IMMUNE-SYSTEM

A simple cellular automata model has been constructed to investigate t he interactions between the two T-helper subset cell types (T(H)1 and T(H)2) in a lymph node during chronic parasitic infection. The model e xhibits behavior similar to a phase transition as a function of the an tigenic 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 den sity then one or other of the T(H) subset cells becomes dominant and f orms a single, connected, infinite cluster (equivalent to a ''ferromag netic'' phase). Much of the phenomenological behavior of the model is seen to be in good agreement with that observed in animal models of pa rasitic infection.