Two binary-encoded models describing some aspects of the coevolution between an artificial immune system and a set of antigens have been proposed and analyzed. The first model has focused on the coevolution between antibodies generating gene libraries and antigens. In the second model, the coevolution involves a new population of self molecules whose function was to establish restrictions in the evolution of libraries’ population. A coevolutionary genetic algorithm (CGA) was used to form adaptive niching inspired in the Coevolutionary Shared Niching strategy. Numerical experiments and conclusions are presented.