Biology Reference
In-Depth Information
Brain
Spinal cord
Sympathetic
neurons
Sympathetic
nerve terminal
Adrenergic
receptor
Secondary
lymphoid
organ
NE
NE
NE
NE
release
Immune cells
Antigen
Immune
cells
Figure 5.1 Communication between the nervous and immune systems.
Upon antigen
exposure, immune cells are activated to secrete cytokines that deliver a signal to the brain.
The SNS is activated centrally to send a signal back to the periphery via sympathetic nerves
that release NE in close proximity to the immune cells that express an adrenergic receptor to
bind it. The binding of NE to an adrenergic receptor on an immune cell modulates the level
of signaling intermediates that regulate gene expression, which in turn changes the level of
immune cell activity and function.
premotor neurons located in the brainstem, pons, and hypothalamus, which are areas
within the CNS that are known to be activated by immune stimuli
[19,20]
. In bone
marrow, these neurons project to sympathetic preganglionic neurons in the interme-
diolateral cell column of the T8-L1 spinal cord, which sends extensions to thora-
columbar paravertebral sympathetic ganglionic neurons
[21]
. In the thymus gland,
sympathetic innervation is received from the cervical and upper thoracic sympathetic
chain ganglia
[22,23]
. In the spleen, sympathetic preganglionic neurons arise from
the T1-T12 region of the thoracic spinal cord
[24]
, and provide input to the post-
ganglionic splenic nerve
[25]
. Finally, individual lymph nodes receive sympathetic
input from postganglionic neurons that are associated with specific regions of the
body where the lymph node is located
[26,27]
.
In contrast to sympathetic innervation of lymphoid tissue, evidence to date shows
no parasympathetic or sensory input from either the vagus nerve or dorsal root ganglia
[25,28,29]
, except in lymph nodes, where they may receive neural sensory afferents
[30]
. Thus, the SNS appears to provide the only pathway for direct neural modulation
of immune-cell activity.
