Mechanisms of cutaneous inflammation. Interactions between epidermal cytokines, adhesion molecules, and leukocytes

How do T cells find their way to the epidermis? Ever since a special relationship between T cells and epidermis was first postulated, it has been assumed that T-cell trafficking through skin occurs as a matter of course, and that the exaggeration of this process may explain the histopathologic features of many diseases characterized by T-cell infiltration of skin.1,2However, the molecular basis for the affinity of T cells (and, indeed, of other bone marrow-derived leukocytes) for epidermis has remained obscure. Recently, several groups have contributed an important piece to the T cell-epidermis puzzle by focusing on the role of a group of glycoproteins collectively called adhesion molecules.3-6Many of these molecules are members of the integrin family of proteins (based on molecular relationships), which, in turn, are thought to belong to the immunoglobulin gene superfamily.7The integrins are a heterogeneous group of proteins that appear to