blood vessel endothelium at sites of infection expresses selected molecules P selectin and ISA lectin leukocytes such as neutrophils Express the ligand for selectins in the form of the silyl aidid lewis x carbohydrate a selects the binding of the endothelial selectins to s lex is weak and cannot hold the cell against the flow of blood instead the cell rolls along the wall of the blood vessel making and breaking many interactions with the selectins you