Cutaneous Lymphocyte-assiciated Antigen (CLA) is a 140 kD homodimer protein recognized by a unique mAb, HECA-452. It is expressed on T lymphocytes in skin, subsets of peripheral blood memory T cells, NK cells, memory B cells and dendritic cells, as well as on monocytes, granulocytes and activated endothelial cells. CLA is a carbohydrate epitope of sialic acid and fucose-modified P-selectin glycoprotein ligand-1 (PSGL-1), a surface glycoprotein expressed on majority of peripheral blood leukocytes. CLA is a subset ligand for E-selectin, P-selectin, and L-selectin. It plays a role in memory lymphocyte homing, tethering, and rolling. Treatment of activated HUVEC cells with HECA-452 antibody inhibits lymphocyte adhesion. The HECA-452 antibody is cross-reactive with mouse CLA and is suitable for staining formalin-fixed paraffin embedded tissue sections.