GLYCOPHORIN A PROTECTS K562 CELLS FROM NATURAL-KILLER-CELL ATTACK - ROLE OF OLIGOSACCHARIDES

Glycophorin A is a protein with an abundant glycosylation (60% carbohy drate by weight), and studies have suggested that resistance of target cells to natural killing may be correlated with the level of glycopho rin A expression, To assess the role of glycophorin A and of its carbo hydrates in sensitivity to lysis by natural killer (NK) cells, the gly coprotein was inserted into the membrane of K562 target cells using el ectropulsation. Peripheral blood lymphocytes were used as effector cel ls. When glycophorin A was inserted into the membrane, the level of re sistance to NK cell attack increased with the number of glycophorin A molecules electroinserted. The resistance to lysis was not due to a de fect in target cell effector cell binding, Electroassociation of glyco phorin A did not cause a decrease in the expression of either ''positi ve signals'' for NK cells (such as CD71, CD15, and CD32 antigens) or c ellular adhesion molecules (CD18, CD29, CD54, and CD58), Furthermore, electroinsertion of glycophorin A did not trigger any ''negative signa ls,'' such as class I HLA antigen expression. Finally, it was shown th at the sialic acid and O-linked oligosaccharides of glycophorin A did not play any role in its effect against NK cells. Conversely, the uniq ue N-linked oligosaccharide was shown to be essential for resistance t o occur.