Flat ECs found in non-specialized regular postcapillary venules
in the skin also mediate constitutive immune cell trafficking under steady state conditions, albeit to a much lesser extent than do HEV ECs.
(I) Circulating naive T (Th0) cells and regulatory T cells (Tregs) migrate to the parenchyma of draining lymph nodes via specialized postcapillary venules
called high endothelial venules (HEVs).
Granger, "Hypercholesterolemia promotes P-selectin-dependent platelet-endothelial cell adhesion in postcapillary venules
," Arteriosclerosis, Thrombosis, and Vascular Biology, vol.
Together, the arterioles, associated capillary network, and postcapillary venules
form a functional unit called the microcirculatory or microvascular bed of that tissue.
The first reports of eczematous inflammation within congenital malformations of postcapillary venules
appeared in the mid-1990s with descriptions of dermatitis within nuchal-occipital port wine stains (PWS) in children (1, 2).
It involves the small blood vessels and postcapillary venules
. More than 70% of cases are related to drug use, underlying diseases, infection, and malignancy.
Increased permeability results mainly from actions of histamine on postcapillary venules
, where histamine causes the endothelial cells to contract and separate at their boundaries (Goodman-Gilman 1990).
Circulating leukocyte transmigration (also called extravasation or diapedesis) through the BBB occurs primarily at postcapillary venules
and is characterized by a multistep adhesion/migration cascade (Figure 1) [25,26].
In Type III reaction, complexes formed by the drug or its metabolite and specific IgG and IgM antibodies developed against these are deposited in postcapillary venules
. In Type IV reactions most of which are observed as skin findings are mediated by T lymphocytes which have gained sesitivity against the drug (10).
Another notable feature is the use of a simple off-the-shelf tube that is the size (300 [micro]m) and shape of postcapillary venules
where endothelial cells are stimulated by inflammatory stimuli.
Amazingly, he demonstrated that nothing happened in the capillaries but that there was separation of the endothelial cells in postcapillary venules
, which was the pathogenesis of the vascular leak; this totally unexpected observation is widely regarded as one of the major discoveries in experimental vascular pathology.