Theoretical Models of Immune Processes - Immunological Computation: Theory and Applications - page 27

Chapter 2
Theoretical Models
of Immune Processes
A feature of the adaptive immune response is its ability to “remember” its encoun-
ters with antigens to achieve a faster response when the same antigen is confronted
at a later time. However, the mechanisms involved in this behavior are not fully
understood. h ere are several theories in the literature about how this behavior is
achieved (Burnet, 1959; Celada and Seiden, 1996; Matzinger, 2002; Oprea and
Perelson, 1997; Varela and Stewart, 1990).
One hypothesis states that B lymphocytes that have reacted to an antigen simply
remain in a dormant state for years, waiting for a recurrence of the same antigen.
It is known that B lymphocytes can remain in a memory state for periods of weeks
or possibly months; however, it is not known if they can survive for years without
being stimulated. Some immunologists think that a kind of internal restimulation
keep this immune memory preserved for a long time. Another hypothesis suggests
that the antigen itself (or some partially degraded form) is sequestered in lymph
nodes and other organs and stimulate the immune system through periodical expo-
sure to the antigen, thereby reinforcing the memory.
In the following sections, some works intended to model various immunologi-
cal principles and mechanisms are described to better understand the biological
processes and simulate its dynamic behavior during the immune response.
2.1 Clonal Selection Theory
Burnet (1959) proposed “clonal selection theory” to explain the proliferation of
immune cells in the presence of an antigen. h is theory states that an antigen
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