Sulfation and sialylation requirements for a 120 kDa glycoprotein, an endothelial ligand for L-selectin in porcine peripheral lymph nodes

Leukocyte recruitment from blood into peripheral lymph nodes is controlled in part by a specific interaction of lymphocyteassociated L-selectin with endothelial cell receptors known as peripheral addressins. OlyCAM-1 (sgpSO) and CD34 (sgp90) in murine lymph nodes and a 105 kDa CD34 in human tonsils have been identified as peripheral addressins. We have characterized a 120 kDa protein from porcine lymph nodes. Validation of the 120 kDa porcine molecule as a peripheral addressin was based on its ability to bind MECA-79, a monoclonal antibody previously used to isolate peripheral addressins from mouse and human tissues and to a human L-aelectin-Fc chimera. Desialylation of the 120 kDa protein with neuraminidases significantly reduced its binding to L-selectin chimera but had no visible effect on binding to MECA-79. When isolated from lymph node expiants cultured in , the presence of chlorate, a metabolic inhibitor of sulfation, the 120 kDa protein displayed dramatically reduced ability to bind either L-selectin chimera or MECA-79, revealing that sulfation is necessary for the production of the functional molecule. These findings suggest that the porcine 120 kDa ligand represents a porcine CD34 homolog similar to other L-selectin-binding CD34 glycoforms previously observed in murine and human lymph nodes.