We have examined the vasculature of 12 human adenoids and the expressi
on and distribution of four endothelial adhesion molecules, ICAM-1, VC
AM-1, P-selectin and E-selectin, in tissue sections using histology, i
mmunocytochemistry and immunoelectron microscopy (IEM). The connective
tissue septa and septula contained arterioles, veins and efferent lym
phatics. Branches of arterioles supplied lymphoid follicles and divide
d into sub- and intraepithelial capillary plexuses which drained into
interfollicular venules, mostly high endothelial venules (HEV), before
joining larger veins. No afferent lymphatics were observed entering t
he adenoid. Although ICAM-1 was widely distributed in the tissue, it w
as preferentially expressed on luminal aspects of HEV. E-selectin was
found only in a few areas on HEV and subepithelial capillaries, wherea
s P-selectin was strongly expressed on segments of HEV, adjacent small
venules and a few follicular capillaries. IEM showed the localisation
of VCAM-1 on the components of the perivascular sheath, but not on th
e endothelium, of some HEV and capillaries. Its strongest expression w
as on follicular dendritic cells (FDC). These findings showed that in
addition to HEV, lymphocyte-binding molecules are expressed on other s
egments of adenoid vasculature and their distribution and intensity of
expression varies. In the non-inflamed adenoid, the VCAM-1 does not s
eem to participate in the adhesive mechanism of recirculating lymphocy
tes to the endothelium which, in this study, lacked the expression of
VCAM-1 in all vessels.