NONSPECIFIC T-CELL HOMING DURING INFLAMMATION IN ATOPIC-DERMATITIS - EXPRESSION OF CUTANEOUS LYMPHOCYTE-ASSOCIATED ANTIGEN AND INTEGRIN ALPHA-E-BETA-7 ON SKIN-INFILTRATING T-CELLS

Atopic dermatitis (AD) is a chronic skin disorder, characterized by in filtration of activated memory CD4(+) T cells into skin. A model to st udy the onset of allergic inflammation in a patient with AD is the ato py patch test (APT), in which, by epicutaneous application of aeroalle rgen, an eczematous reaction is induced in 50% of sensitized patients with AD. Extravasation of T cells into skin is thought to be criticall y dependent on expression of the surface molecule cutaneous lymphocyte -associated antigen (CLA), which recognizes and binds its ligand E-sel ectin on endothelium. We studied the dynamics of expression of CLA and the gut homing receptor alpha E beta 7 (HML-1) on T cells in the skin of patients with AD and in APT reactions and nickel and sodium lauryl sulfate patch test reactions by means of immunohistochemical double s taining of skin biopsy specimens. The results show an increase in the number of CD3(+) T cells in the lesional skin of patients with AD, APT reactions, and nickel and sodium lauryl sulfate patch test reactions as compared with nonlesional skin of the same patients and nonatopic i ndividuals. In contrast, the percentages of CLA(+) T cells in the lesi onal skin of patients with AD, in the APT reactions, and in sodium lau ryl sulfate and nickel patch test reactions were decreased. In additio n, we found a marked expression of alpha E beta 7 by T cells present i n skin, indicating a nonspecific influx of T cells during allergic ski n inflammation. We propose that during allergic skin inflammation CLA expression is not a prerequisite for cutaneous T-cell infiltration. CL A expression may be important for T cells to extravasate from blood in to skin during immune surveillance or for retention of allergen-specif ic T cells in skin.