IMMUNOHISTOLOGY OF SKIN PATHERGY REACTION IN BEHCETS-DISEASE

The immunophenotypic characteristics of the skin pathergy reaction (SP R) at 48 h in BehCet's disease (BD) were investigated in 12 patients w ith BD and in five controls. The findings in 11 positive and one negat ive SPR lesions of patients with ED were evaluated in comparison with those of normal adjacent skin and with the negative pathergy biopsies from the controls. Positive SPR biopsies showed variable epidermal thi ckening and cell vacuolization, as well as subcorneal pustule formatio n, In the SPR dermis, a variable dense focal mononuclear cell (MNC) in filtrate was seen around vessels and skin appendages, extending into t he deep dermis. The MNC infiltrate was predominantly composed of T lym phocytes and monocytes/macrophages. The majority of the T lymphocytes were CD4(+), and almost all expressed CD45RO, Approximately half of th e infiltrating cells strongly expressed HLA-DR, Neutrophils constitute d less than 5% of the infiltrating cells, but were present as clusters of elastase-positive cells at the needle-prick sites. Vessels within the lesion showed marked congestion and endothelial swelling, The endo thelial cells expressed ICAM-1 strongly, and E-selectin moderately, VC AM-1 was not expressed on endothelial cells. The basal and mid-epiderm al layers of keratinocytes expressed HLA-DR and ICAM-1 strongly, parti cularly so in areas close to the dermal MNC infiltrates, In negative p athergy biopsies, there were increased numbers of neutrophils and a fe w small clusters of macrophages and T lymphocytes only at the needle-p rick site, and the endothelial cells of vessels close to these areas e xpressed E-selectin weakly, The immunohistological findings of the SPR appear to indicate an augmented antigen-independent non-specific indu ction phase of the inflammatory response. Absence of VCAM-1 expression by endothelial cells suggests that direct epidermal injury is the cau se of the cutaneous inflammation.