High endothelial venules in involved and uninvolved psoriatic skin: recognition by homing receptors on cytotoxic T lymphocytes.

We report the presence of tannic acid staining material in the intercellular spaces between adjacent endothelial cells of the high endothelial venules (HEVs) in psoriatic skin, which appears to be recognized by T8 (cytotoxic/suppressor) lymphocytes, as the presence of HEVs was found to be related to the presence of T8 lymphocytes in the epidermis. As HEVs with similar tannic acid staining material were also observed in peripheral lymph nodes, we suggest that this material may serve as a marker for HEVs recognized by the T8 lymphocyte subset. T8 + lymphocytes were found in the epidermis at 5 min and I h after tape-stripping of uninvolved skin of psoriatic patients with active disease, but not until 24 h in a psoriatic patient in remission. The prior existence of HEVs in uninvolved psoriatic skin could account for the rapid egress of T8 lymphocytes from the vasculature to the epidermis in response to trauma.