Bovine γ/δ T cells bind E-selectin via a novel glycoprotein receptor: First characterization of a lymphocyte/E-selectin interaction in an animal model

E-Selectin is an inducible adhesion protein expressed by endothelial cells and recognized by leukocytes during their extravasation from the blood into inflamed tissues. Originally, E-selectin was defined as a myeloid cell-specific adhesion protein, but recent studies have shown it to be recognized by human lymphocytes as well. These lymphocytes represent a memory T cell subset and have been shown to express the HECA-452 carbohydrate epitope (CLA⁺ lymphocytes). We extend these findings and show that ruminant γ/δ T cells bind E-selectin as well; and we provide preliminary evidence that this interaction is mediated by a novel glycoprotein receptor on the lymphocyte. Unlike conventional T cells (α/β T cells), γ/δ T cells from neonatal and mature animals bind E-selectin, suggesting that prior antigen stimulation and differentiation to a memory lymphocyte are not required for this interaction. Neuraminidase treatment of the γ/δ T cells or addition of ethylenediaminetetraacetic acid (EDTA) to the assay abrogates binding demonstrating the importance of sialic acid and divalent cations, which is consistent with other E-selectin-mediated adhesion events. However, previously defined E-selectin carbohydrate ligands, such as sialyl Lewis x on neutrophils and the HECA-452 epitope on human memory lymphocytes, are antigenically different than the carbohydrates on ruminant γ/δ T cells since the mAbs CSLEX and HECA-452 do not recognize these cells. Protease treatment of γ/δ T cells significantly inhibits their binding to E-selectin; however, previously characterized adhesion glycoproteins, such as L-selectin, CD44 and CD18, are not involved in the adhesive event. An E-selectin affinity column purities a single dycoprotein of 250 kD (280 kD under reducing conditions) from γ/δ T cell detergent lysates. Neuraminidase digestion of the 250-kD product as well as EDTA abolishes binding to E-selectin Finally, E-selectin expression in vivo appears to mediate γ/δ T cell accumulation. Stimulation of bovine skin with tumor necrosis factor α induced an increase in E-selectin expression that was associated with an influx of γ/δ T cells at the same site.