First, the immune system is aninformantfor the nervous system. It provides
vital information about infections, damage, and other perturbations that occur in
any part of the organism. If, as proposed inSection 2, the capacity to respond to
pathogens and other sources of damage constitutes one of the strongest evolu-
tionary pressures on organisms, then conveying information to the nervous
system about the immunological status of the host is vital. Second, the immune
system is anexecutantfor the nervous system: it realizes distinctive activities
indispensable for the functioning of the nervous system, such as elimination of
dead cells, repair, and so on. Third, and most crucially, the immune system is
amessengerfor the nervous system: not only does the nervous system resort to
the molecular communication pathways of the immune system (cytokines) but
it makes use of the unique feature of immune cells, namely their mobility, which
allows them to reach any part of the organism and to deliver complex messages
there. I suspect that, in coming years, cognitive functions mediated by this
unique mobility of immune cells will be uncovered.
Current research in neuroimmunology raises other philosophically interest-
ing issues, which could not be examined here due to space restrictions. These
include how the nervous and the immune system interact in the construction of
biological individuality and rethinking central physiological concepts such as
homeostasis in light of the crosstalk between these two systems, among many
other questions. Again, the aim of this section was simply to convince the reader
that neuroimmunology is full of philosophical promise.
Philosophy of Immunology 63