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

Although cutaneous lymphocyte-associated antigen (CLA) is thought to be spe cifically expressed on skin "homing" T cells, it has become clear that CLA is not directly involved in binding to E-selectin but represents an excelle nt marker for high levels of fucosyltransferase VII (Fuc-TVII): Fuc-TVII ca n 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 ant ibody for Fuc-TVII, we investigated whether expression of Fuc-TVII could be selectively detected in various CLA(+) cell lines and peripheral blood T c ells. Fuc-TVII was readily detected in the cytoplasm, but not in the membra ne, of CLA(+) cell lines. Cytoplasmic Fuc-TVII expression was also detectab le in both CD4(+) and CD8(+) T cells purified from peripheral blood mononuc lear cells. Nevertheless, there were significant numbers of CLA-expressing CD4(+) or CD8(+) T cells that did not coexpress Fuc-TVII, and vice versa: e ither the CD4(+) or the CD8(+) T cell population consisted of a variable ra tio of CLA(+) Fuc-TVII+, CLA(+) Fuc-TVII-, and CLA(-) Fuc-TVII+ cells; and CLA(+) Fuc-TVII- cells were the most abundantly identifiable phenotype in p eripheral blood CD4(+) and CD8(+) T cells. Thus, according to their express ion pattern, skin "homing" T cells can be subdivided into at least three po pulations, CLA(+) Fuc-TVII+, CLA(+) Fuc-TVII-, and CLA(-) Fuc-TVII+ cells. Our study provides convincing evidence that skin "homing" T cells are pheno typically heterogenous and that Fuc-TVII expression, in combination with CL A expression, is a useful phenotypic marker for identifying skin "homing" T cells in mixed cell populations.