Evidence from a variety of disciplines supports a bidirectional communication between the nervous
system and the immune system. Various kinds of environmental challenges, as perceived by the nervous system can affect an
animal's ability to fight off pathogens that may compromise the immune system and result in disease or mortality.
Neural-immune interactions have applications for cetaceans in the wild and for those kept under human care. Environmental
pollutants (oil, industrial toxins, noise), extreme changes in temperature, housing conditions, social interactions, as well
as the level of difficulty in learning a task, have been shown to cause changes in immunocompetence in other mammals.
Our laboratory has investigated aspects of both the nervous and immune systems in cetaceans including:
general morphology of cetacean lymphoid organs at the light and electron microscopic levels, the autonomic innervation of
lymphoid organs at the light and electron microscopic levels, characterization of lymphocytes in cetacean peripheral blood,
functional lymphocyte studies, and molecular characterization of important immunologic proteins. Morphology of cetacean
lymphoid organs at the light and electron microscopic levels reveals similar structure to lymphoid organs of other mammals
with some unique features. Innervation of lymphoid organs reveal postganglionic sympathetic nerve fibers containing tyrosine
hydroxylase (TH) (the rate-limiting enzyme for catecholamine synthesis) and neuropeptide-Y are closely associated with
lymphoid cells in these organs. Moreover, TH-positive nerve terminals are observed in close apposition with lymphocytes in
the spleen at the electron microscopic level. Ligand binding studies show the presence of beta adrenergic receptors on
cetacean peripheral blood lymphocytes. Major histocompatibility class II expression reveals constitutive expression on T
lymphocytes as well as B lymphocytes. At the molecular level, the T helper cell surface protein, CD4, reveals differences in
immunoglobulin domain structure with an increase in potential glycosylation sites and unique substitutions in the
cytoplasmic domain. Preliminary functional investigations show a decrease in proliferation of lymphocytes after incubation
with isoproterenol (a beta adrenergic agonist).
Using available cetacean-specific immunologic reagents that we and our collaborators have developed we
are currently measuring immunocompetence and nervous system activation in cetaceans, before, during, and after environmental
challenges. Pharmacologic and behavioral means may be applied to lessen the effects on the nervous and immune systems and
help to promote health and viability in these mammals.