among many others (Eom and Parichy 2017). Overall, this view suggests
interesting and important distinctions about the different selective pressures
that might have existed at the origins of nervous, endocrine, and immune
systems in metazoans. It is likely that some types of messages can be delivered
by one system only: for example, high-speed communication is best realized by
the nervous network, while other processes such as pathogen clearance and
tissue repair require the unique mobility of immune cells. All this constitutes an
invitation to explore not only the similarities between the nervous, immune, and
endocrine systems but also their complementarities, as well as the means that
evolved to coordinate these systems characterized by their different commu-
nication channels. Among other benefits, such research could constitute an
important contribution to current scientific and philosophical discussions
about how and why nervous systems originated in the animal world (Miller
2009; Keijzer et al. 2013; Godfrey-Smith 2016) by enriching the context of this
question with considerations about possible complementarities (and possible
trade-offs as well) between the nervous system and other bodily systems.
5.4.5 Control: Does the Nervous System Control the Immune
System or the Other Way Around?A question slightly different from the four others yet important in this discus-
sion is control. Many neuroimmunologists switch from the description of
intimate interactions between the nervous and the immune system to the idea
that one system controls the other (Chavan and Tracey 2017). When describing
what he sees as the emerging field of immunopsychiatry,Pariante (2015)
suggests that this domain, by giving prominence to the immune system, reverses
what“governs”and“is governed.”
It should be clear, however, that interactions between two systems and
control by one system over another are two entirely different things. It is not
because recent research has shown that the immune system could influence the
nervous system and its behavior that we should conclude that the immune
system controls the nervous system let alone behavior. More data would be
needed to demonstrate control though it is not entirely clear which data could be
considered conclusive in that case. Moreover, the choice between the“control-
ler”and the“controlled”seems to be more dependent on the disciplinary
background of the person making the claim than on anything else. Personally,
I don’t see the need to attribute control to one system or another.
In summary, we have singled outfive questions in the neuroimmunological
literature and suggested that distinguishing them was useful not only as
a conceptual clarification of current research in that domain but also as an
60 Elements in the Philosophy of Biology