  In this paper we made a review of some papers about probabilistic regulatory
networks (PRN), in particular we introduce our concept of homomorphisms of PRN
with an example of projection of a regulatory network to a smaller one. We
apply the model PRN (or Probabilistic Boolean Network) to the immune system,
the PRN works with two functions. The model called ""The B/T-cells
interaction"" is Boolean, so we are really working with a Probabilistic Boolean
Network. Using Markov Chains we determine the state of equilibrium of the
immune response.
