Biomedical Engineering Reference
In-Depth Information
Computer simulations of Eqs. [A1]-[A6] indeed show, not surprisingly, that
monitoring information on progress toward multiple goals can improve immune
performance, in the sense of decreasing average harm E. The system "automati-
cally" adjusts itself for efficient combat when faced by pathogens of varying
virulence. Moreover, even a given pathogen is better handled, compared with
the control "no information model," by secreting
N
only when it is needed and
turning secretion off when the pathogen threat is no longer serious (4).
I have described a simple model that shows how the deployment of a given
immune system arm (effectors working via noxious chemicals) can use sensed
information to improve performance. This material is summarized in Table 1.
See (4) for a model that illustrates how sensed information can bias an immune
system to choose appropriately among a variety of possible effector arms.
Table 1
. Possible immune system "goals" and how they might be achieved
SENSING GOALS
Goal To be sensed
Identify dangerous pathogen High harm
H
AND (low noxious
N
OR
high pathogen
P
)
Identify harm to self High harm
H
AND (high noxious
N
OR
low pathogen
P
)
PERFORMANCE GOALS
Goal Action
Kill dangerous pathogens Positive feedback to
N
secretion when
sensors reveal dangerous pathogen and
pathogen killing
K
Avoid harm to self Negative feedback to
N
secretion when
sensors reveal dangerous pathogen and
pathogen killing
K
Note
. Actuator effect of sensor information is mediated by cytokines.