Biology Reference
In-Depth Information
(B)
(A)
(C)
10 microns
Figure 4.2
TEM images of CP. (A) 24,000x image of CP frond, with microvilli (#) and
cilia (*) localized on the surface; (B) 54,800x image of cell junction; (C) 14,000x image of
cytoplasm, displaying densely packed organelles.
by monitoring the overall biodistribution of drugs and toxic compounds, for which it
uses a full complement of metabolizing enzymes (including Phase I-III enzymes) for
functionalization, conjugation, and transport of drugs. Examples of detoxifying mech-
anisms of the CP include the utilization of (a) high concentrations of glutathione,
cysteine, and metallothioneins that potently sequester toxic agents circulating in the
CSF; (b) protective enzymes such as superoxide dismutase, glutathione-s-transferase,
and glutathione peroxidase and reductase to provide a barrier protecting against free-
radical oxidative stress; and (c) organic ion transport systems and multidrug resistance
proteins for filtering detrimental substances from the CSF.
4.3 Choroid Plexus and the Immune System
Recently, maintenance of a tolerant or responsive immunological status of the brain
has been designated as another important neural homeostasis function of the CP
[10]
.
Although the CNS has long been thought of as an immune-privileged organ, such
immunity is not absolute. Indeed, it is well documented that the CNS can mount an
immune response within the brain tissue. The immune reaction is tightly controlled
by the CNS via blockade of immune-cell entry into the brain, with such responsibility
largely borne by the blood-brain barrier (BBB) and CP blood-CSF barrier. Whereas
immune-cell migration into the CNS is almost absent under physiological conditions,
immunocompetent cells are able to breach the BBB and CP blood-CSF barrier and
