  We develop a modular mean field theory for a minimalistic model of the
idiotypic network. The model comprises the random influx of new idiotypes and a
deterministic selection. It describes the evolution of the idiotypic network
towards complex modular architectures, the building principles of which are
known. The nodes of the network can be classified into groups of nodes, the
modules, which share statistical properties. Each node experiences only the
mean influence of the groups to which it is linked. Given the size of the
groups and linking between them the statistical properties such as mean
occupation, mean life time, and mean number of occupied neighbors are
calculated for a variety of patterns and compared with simulations. For a
pattern which consists of pairs of occupied nodes correlations are taken into
account.
