Information Technology Reference
In-Depth Information
the same manner like the antibodies interact with each other and this way the
concentration levels of antigens are also able to be modified.
For both types of objects the lifetime attribute values are just gathered during
experiments. The values of lifetime do not influence the activity of the system
but they are introduced only for easier and more thorough observation of the
system behavior.
2.1
The Main Loop of the Process
At the beginning of the experiment an initial number of objects representing
different types of antibodies is randomly generated and their attributes are set
to initial values. Then the process of life starts. The main loop models the life
of the organism. The main task of the loop is to execute the dynamics and
metadynamics of the model by updating the levels of concentrations in all the
existing objects. During the execution of the main loop some of the objects
disappear when their concentration shrinks below the minimum threshold. The
deleted objects are replaced by mutated clones of those which concentration
is high. The concentration shrinks when the object representing given type of
antibodies is suppressed by the other types. When the object is stimulated its
concentration grows but it does not grow to infinity. In our experiments the
upper limit of concentration level was set to 9999.
2.2
The Antibodies Relationships
There are rules in the system steering the levels of concentrations. They are
based on anity between paratopes and epitopes of different types. It is im-
portant to stress that in contrast to other network models the rules depend on
the number of other types that a type interact with and they do not depend on
the concentration of those types. This is an unusual assumption because in the
existing models of the networks the concentration of antibodies plays the signifi-
cant role in suppression and activation mechanisms. However a rule promoting a
growth of diversity in the population of antibodies could stimulate the system to
build more stable nets of stimulative relations between the molecules. In such a
net a large number or even most of the relations are redundant i.e. lost of one or
two types of antibodies does not cause gaps in the chains of relations. Therefore
in the presented approach the concentration is responsible just for the lifetime
of the particular type of antibodies or antigens.
When the value of the anity between any two objects is above the specified
level the rule is activated and the object's concentration is modified. There are
five rules of stimulation and suppression defined. The first two rules describe
interactions between types of antibodies while the three latter are used when
objects representing types of antigens are introduced into the system. All of
them define values which the concentration will be increased or decreased by. In
addition they are not disjoint i.e. more than one of them can be satisfied simul-
taneously for one object. In that case the values from the rules are summarized
and the cumulative modification of the concentration is evaluated.
