Increased susceptibility of periodate-treated tumour cells to human but not to mouse or rat natural killer cells.

Abstract

Treatment of intact cells in the cold with low concentrations (1 mM) of sodium meta periodate (PI) selectively oxidizes the surface-exposed sialic acid residues to the corresponding aldehydes. Such treated tumour cells show greatly enhanced sensitivity to lysis by fresh human NK cells but not to mouse or rat NK cells. Reduction of the PI-treated cells with sodium borohydride (NaBH4) reduced their NK sensitivity to that of untreated cells. In target conjugate formation assays PI-treated tumour cells displayed a higher binding capacity than control cells or PI+NaBH4-treated cells to both mouse and human effector cells. Neuraminidase treatment of K562 and Molt-4 increased target susceptibility to human NK cells but not to mouse, whereas the susceptibility of Yac-1 cells was left unchanged using both human and mouse effector cells. The same pattern of reactivity is shown in the target binding assay. These findings indicate that subtle molecular changes in the surface-exposed carbohydrates of target cells might have a fundamental impact on their sensitivity to lysis by NK cells from certain species, and that in cross species effector-target combinations a higher binding capacity is not sufficient for increased lysis to occur.