Abstract
High endothelial venules (HEVs), which are in the parafollicular region of the lymphoid tissues, including tonsils, play a significant role in immune response by providing the pathway for lymphocyte recirculation or homing from blood stream to lymphoid tissues parenchyma.
Previously much attention has been given to the study of HEVs of human and other species. HEVs of tonsil have been researched in human and other kinds of animals. However, the histochemical structure or the function of basal lamina of HEV has not been studied in human palatine tonsil. The present study shows the histochemical properties of the basal lamina in HEVs of human palatine tonsils by using cationic colloidal iron staining.
Palatine tonsils were obtained from 8 patients by tonsillectomy in Okayama University Hospital from 1999 to 2000. Some sections of these samples were applied to enzyme digestion prior to cationic colloidal iron staining.
In the sections stained with cationic colloidal iron at pH1 .5, a distinct Prussian blue reaction was observed in the basal lamina of HEV . Digestion with hyaluronidase or collagenase eliminated the colloidal iron staining of the basal lamina of HEV . Treatment with chondroitinase ABC reduced colloidal iron staining. Digestion with neuraminidase, keratanase, or heparitinase did not affect the colloidal iron reaction of the basal lamina.
The results suggest that negatively charged sites in the basal lamina of HEV derive mostly from hyaluronic acid and chondroitine sulfate, which constitute sulfated proteoglycan complex firmly binding collagen molecules. Intensely negative-charged basal lamina containing abundant sulfated proteoglycan may involve lymphocyte migration after passing through the endothelial cell layer.
