Biomedical Engineering Reference
In-Depth Information
The classical "command view" of cytokines suggests that suitable cytokines
can be administered to patients in order to alter harmful physiological condi-
tions. A problem here comes from the pleiotropic nature of cytokine action. Ele-
vation of a cytokine's concentration may have harmful additional effects, aside
from the desired response. Moreover, varying backgrounds of other cytokines
may alter the "standard" consequence of administering a given cytokine.
There is an alternative approach to "commanding" an immune response that
seems to the physician to be appropriate. The physician can try to present infor-
mation to the patient's physiological systems, perhaps by suitably chosen and
timed cytokine doses, perhaps by other means (see below), so that an appropri-
ate response to that information would yield a desired affect. For example, it
may be thought appropriate to treat an allergy patient by shifting Th2 dominance
to Th1 dominance. Attempts can be made to command this shift by administer-
ing cytokines that are known to favor Th1 and/or suppress Th2. Alternatively,
one might inject killed bacteria that normally evoke a Th1 response, or inject a
panel of cytokines (with proper doses and timings) that are evoked by binding of
characteristic epitopes of Th1-inducing pathogens. Countering physiological
information that lead to harmful physiological phenomena can be regarded as an
alternative version of physicians' classical approach to illness, trying to reverse
the harmful symptoms.
6.3. Combating Multiple Organ Dysfunction
Is there any evidence that the "chemotactic scheme" of ยง5, randomness with
drift, has actually been adopted by some organisms to improve performance
with respect to multiple goals? Remarkably, there is a hint of such evidence
from Buchman (this volume, Part III, chapter 7.2) in multiple organ dysfunction
syndrome (MODS). He writes, "analysis suggested that the coupling between
heart and lungs was not fixed but rather dynamic.... The inference is that health
may be associated with a search through the space of possible interactions to
find the one best suited to current physiologic challenges." It might just be that
the suggested directed random search for better performance in the face of mul-
tiple goals is a fundamental principle of human physiology.
One could even speculate further. Buchman gives as one seeming inade-
quacy of conventional MODS treatment that mortality is increased when cal-
cium is administered to correct the subnormal values of calcium characteristic of
sepsis. In view of such findings, perhaps it is worth thinking of experimental
intensive care with a "chemotactic strategy." This would involve continually
shifting and partially random choices of therapies to adjust abnormal values of
the variety of physiological variables that are traditionally sensed by intensive
care monitors. Shifts are less frequent when the present tactic is sensed to be
