Increased sensitivity of cholera toxin B treated K562 cells to natural killer cells

Cholera toxin B-subunit (CTB) treatment of K562 erythroleukemia cells increased their sensitivity to be killed by NK-92 cells with more than 10%, compared to untreated cells. A similar treatment of non-T, non-B acute lymphoblastic REH leukemia cells, known to be unsensitive to NK cell mediated cytotoxicity, did not have any impact at all. Visualization of the cross-linked gangliosideM1 (GM1) using fluorescent labeled CTB, indicated accumulation of the fluorescence to one cap and a few smaller patches in both type of cells. Additional cross-linking using anti-CTB antibodies further accentuated capping and increased lysis in the case of K562 cells. Blocking experiments performed with anti-MICA/B, ULBP-2 and/or CD59 antibodies could not inhibit the increased sensitivity mediated by CTB.