Biology Reference
In-Depth Information
3. Both decreases or increases of T
A
can obliterate oscillations.
4. Increases, but not decreases, of T
B
remove the pulsatility.
2. Antibody administration
Antibody molecules are made of proteins generated by the immune
system. They are produced and circulated in the bloodstream in
response to agents, usually cells or molecules, that the organism
considers ''not self.'' If these circulating antibodies come in contact with
the agent, they are able to bind specifically to that foreign object—the
target. This binding will result in several possible outcomes: The target
may be inactivated; it may be now more easily destroyed by the immune
system; or the target may now be unable to associate with the tissue.
Accordingly, administration of a compound that acts like an antibody
(Ab) to a certain substance, referred here as S, typically results in the de
facto removal of S from the system. The rate of removal depends on the
specific chemical reaction between Ab and S, and the process can be
simulated by an increase of the elimination rate of S with a certain
reaction-specific factor. The chemical reaction may change the single
half-life pattern into a multiple half-life model (see Chapter 9). However,
the single half-life approximation might still be sufficient in the
simulations or used as a first step towards a more complex model.
To exemplify the concept, we simulated variable removal of the inhibitor
A in the model described by Eq. (10-16) (see Figure 10-19). Three
simulations were performed in which the coefficient clearance rate of
A was increased gradually (90% increase was achieved in less than
3 hours) 4-fold (left), 8-fold (middle), or 16-fold (right) starting at
t
¼
88:00.
Figure 10-19 exemplifies that increasing the elimination rate of a
hormone could be used to simulate infusion of an antibody and almost a
complete removal of one of the nodes. This may result in loss of
periodicity (Figure 10-19, middle, right). The plot in Figure 10-19 (left
panel) also captures a very interesting phenomenon predicted by the
FIGURE 10-19.
Simulated variable infusion (starting at t
88:00) of antibody to the inhibitor A (dotted line) in the
reference model outlined in Eq. (10-16). The plots depict low (left panel), medium (middle panel), or
almost complete (right panel) removal of A.
¼
