Development and characterization of a monoclonal antibody specific for fucosyltransferase VII (Fuc-TVII): Discordant expression of CLA and Fuc-TVII in peripheral CD4+ and CD8+ T cells

Abstract

Although cutaneous lymphocyte-associated antigen (CLA) is thought to be specifically expressed on skin "homing" T cells, it has become clear that CLA is not directly involved in binding to E-selectin but represents an excellent marker for high levels of fucosyltransferase VII (Fuc-TVII): Fuc-TVII can regulate the ability of T cells to migrate into the skin by generating a binding site for E-selectin. In this study, by using a novel monoclonal antibody for Fuc-TVII, we investigated whether expression of Fuc-TVII could be selectively detected in various CLA+ cell lines and peripheral blood T cells. Fuc-TVII was readily detected in the cytoplasm, but not in the membrane, of CLA+ cell lines. Cytoplasmic Fuc-TVII expression was also detectable in both CD4+ and CD8+ T cells purified from peripheral blood mononuclear cells. Nevertheless, there were significant numbers of CLA-expressing CD4+ or CD8+ T cells that did not coexpress Fuc-TVII, and vice versa: either the CD4+ or the CD8+ T cell population consisted of a variable ratio of CLA+ Fuc-TVII+, CLA+ Fuc-TVII-, and CLA- Fuc-TVII+ cells; and CLA+ Fuc-TVII- cells were the most abundantly identifiable phenotype in peripheral blood CD4+ and CD8+ T cells. Thus, according to their expression pattern, skin "homing" T cells can be subdivided into at least three populations, CLA+ Fuc-TVII+, CLA+ Fuc-TVII-, and CLA- Fuc-TVII+ cells. Our study provides convincing evidence that skin "homing" T cells are phenotypically heterogenous and that Fuc-TVII expression, in combination with CLA expression, is a useful phenotypic marker for identifying skin "homing" T cells in mixed cell populations.