  The phenomenon of immunological memory has been known for a long time. But,
the underlying mechanism is poorly understood. According to the theory of
clonal selection the response to a specific invading antigen (e.g., bacteria)
is offered by a specific clone of the cells. Some of the lymphocytes activated
during the primary response remain dormant and keep circulating in the immune
system for a long time carrying the memory of the encounter and, therefore,
these long-lived cells are called memory cells. Proponents of the alternative
network theory maintain that the immune response is offered by a "network" of
clones in a collective manner. In recent years several possible scenarios of
the "structure" and function of the immune network have been considered. We
have developed mathematical models for describing the population dynamics of
the immunocompetent cells in a unified manner. We have incorporated
intra-clonal as well as inter-clonal interactions in a discrete formulation and
also studied a continuum version of this model.
