A role for L-selectin in monocyte activation by Jurkat tumour cells

Monocytes and macrophages can distinguish between tumour cells and non-malignant cells of the same cell type. The surface structures mediating tumour cell recognition and tumour cell-induced cytokine production by monocytes or macrophages are still poorly characterized. The authors previously described N-linked sialic acid-containing carbohydrates associated with CD2 of the CD4+ tumour cell line Jurkat which induced tumour necrosis factor (TNF) secretion by human monocytes. In this report the authors demonstrate a role for monocytic L-selectin in this process. Mannose-6-phosphate, an inhibitor of L-selectin binding, blocked CD2-induced TNF production whereas other ligands for L-selectin (the monomeric monoclonal antibody to L-selectin, DREG-200; inositol hexaphosphoric acid; heparin) amplified CD2-induced secretion of TNF. Polyvalent L-selectin ligands as soluble monoclonal antibody (MoAb) DREG-56, the cross-linked MoAb DREG-200, and the marine algal polysaccharide fucoidin induced TNF production without addition of CD2. Jurkat-CD2 is associated with sialyl Lewis X-related carbohydrates which differ in their expression or composition from that of the non-stimulatory CD2 from non-malignant T cells. Taken together the data presented in this report suggest that-at least in the case of Jurkat-CD2-L-selectin is involved in monocyte activation by tumour typical carbohydrate structures.