Functional cutaneous lymphocyte antigen can be induced in essentially all peripheral blood T lymphocytes

The cutaneous lymphocyte-associated antigen (CLA) is a skin-homing receptor expressed on a minority of memory-type peripheral blood T (PBT) lymphocytes. Induction of high-level CLA expression in PET has previously been difficult to accomplish in vitro. Here we report that constitutive CLA expression could be readily induced in virtually all PET by various polyclonal activators. There was no requirement for accessory cells or addition of other mediators except for IL-2 for maintaining cell survival. Absence of serum in the culture medium was important for optimal induction of CLA. The number of T cells adhering to E-selectin as well as tethering and shear stress resistance under hydrodynamic flow increased in correlation with the level of cell surface CLA expressed. Clonal analysis of CLA induction revealed that in serum-containing medium, which permits the majority of T cells to expand, only a minority of clones did not express CLA. Such T cells could be induced to highly express CLA within 8 days by switching from serum-containing to serum-free medium. This cell-surface phenotype change was closely associated with acquisition of E-selectin ligand activity. Fucosyltransferase VII, which is believed to be important for the generation of the CLA epitope on the P-selectin glycoprotein ligand-1 (PSGL-1) backbone, was shown to be significantly increased in CLA-positive versus CLA-negative T cell populations by PCR analysis. Our findings are consistent with the idea that restriction of CLA expression after activation, rather than positive selection of predetermined T cell subpopulations exposed to restrictive stimulatory conditions in unique microenvironments, may be important in vivo.