T lymphocytes and monocytes bind to keratinocytes in frozen sections of biopsy specimens of normal skin treated with gamma interferon

Abstract

When 2 mm punch biopsy specimens of normal skin are incubated with gamma interferon (IFN-γ), the keratinocytes are induced to express intercellular adhesion molecule-1 (ICAM-1). Lymphocytes and monocytes that express lymphocyte function-associated an-tigen-1 (LFA-1) bind to cultured keratinocytes expressing ICAM-1. We have developed an in vitro adherence assay using frozen sections of normal skin that have been incubated with IFN-γ, and then overlaid by peripheral blood mononuclear leukocytes. Although peripheral blood mononuclear leukocytes do not bind to the epidermal keratinocytes of untreated skin sections, after exposure of the skin to IFN-γ the peripheral blood mononuclear leukocytes prominently bind to the epidermal keratinocytes that express ICAM-1. The binding by peripheral blood mononuclear leukocytes is increased approximately twofold by activation with phorbol ester treatment. The temperature dependence and kinetics of this adherence reaction reveal no binding at 8° C, good binding at 24° C, and optimal binding at 37° C, reaching a maximal extent by 60 minutes. The adherence reaction is blocked either by pretreating the peripheral blood mononuclear leukocytes with LFA-1 antibody or the IFN-γ—exposed skin specimen with ICAM-1 antibody. The immunophenotypic analysis of the adherent peripheral blood mononuclear leukocytes to epidermal keratinocytes revealed that most cells activated by 12- O-tetradecanoyl-phorbol-13-acetate are T lymphocytes, with CD8 + T cells binding slightly better than CD4 + T cells, with a smaller population of monocytes. These results provide additional support for a role of LFA-1, ICAM-1, and IFN-γ in modulating ke-ratinocyte-lymphocyte interactions. This short-term organ culture—frozen section adherence assay system provides a new research tool to explore further possible molecular adhesion mechanisms and cellular interactions involved in trafficking of peripheral blood mononuclear leukocytes in the skin.