  Divergence in antigen response of the immune network is discussed, based on
shape-space modelling. The present model extends the shape-space model by
introducing the evolution of specificity of idiotypes. When the amount of
external antigen increases, stability of the immune network changes and the
network responds to the antigen. It is shown that specific and non-specific
responses emerge as a function of antigen levels. A specific response is
observed with a fixed point attractor, and a non-specific response is observed
with a long-lived chaotic transient state of the lymphocyte population
dynamics. The network topology also changes between these two states. The
relevance of such a long-lived transient state is discussed with respect to
immune function.
