Biology Reference
In-Depth Information
regard to a role of the CNS in regulation of immunity, reference should be made
to early and successful studies dealing with different neuromediator systems of the
brain as they modulate immune function
[50-52]
.
2.5.2 Innervation of Lymphoid Organs
A significant advance in NIB was achieved by detailed studies on the innervation of
lymphoid organs, including not only their external neural input, but also the inter-
nal distribution of nerve fibers and endings within the organs of the immune system
[53-56]
. The notion of “open” synapses located at nerve endings emerged. Certain
stimuli reaching such synapses elicit the release of neuromediators into the imme-
diate vicinity of lymphoid cells and thus bring regulatory information to them via
soluble neurotransmitters (e.g., sympathetic outflow)
[57]
.
2.5.3 Hormonal Immunoregulation
Much effort was made to elucidate the possible efferent pathways of neural immuno-
regulation. The possible immunoregulatory role of hormones was studied by numer-
ous investigators. Currently, abundant information is available in the literature on
this subject, which is summarized in a number of reviews and monographs
[50,58]
.
The general conclusion is that an excess or deficit of almost any hormone will
affect immune function. However, the growth and lactogenic hormone family has
emerged as the hormones of immunocompetence. In contrast, the hormones of the
hypothalamus-pituitary-adrenal axis were proven to have an immunosuppressive
and anti-inflammatory role
[59-62]
. The concept of an integrated neuroimmune reg-
ulatory network gradually emerged on the basis of new knowledge, in the field that
later became known as neuroimmune biology.
Blalock
[63]
and Smith
[64]
discovered the production of classical hormones by
cells of the immune system. Today it is clear that cytokines and chemokines, which
originally were thought to be produced by the immune system, are actually produced
in the CNS as well, and fulfill both pathological and physiological functions
[65,66]
.
Conversely, hormones, neurotransmitters, and neuropeptides are readily produced
within the immune system. However, the production of some soluble mediators of
each of these substances does take place in every organ and tissue in the body. This
sharing of mediators allows the neuroimmune regulatory network to communicate
with each organ and tissue in the body and to coordinate the function of the entire
organism in health and disease
[67]
.
2.5.4 Some Molecular Mechanisms in Immunophysiology
It is obvious from the evidence discussed in preceding sections that lymphoid cells
must have some means of recognizing neural messages. This is fundamental to
the whole problem, and is why the discovery of receptors for neuromediators, hor-
mones, and regulatory peptides on immunocyte membranes was a landmark in NIB
