Resistance of leukemic blasts to lymphokine activated killer (LAK)-mediated cytotoxicity is not related to their adhesion properties.

The expression of adhesion molecules on blasts from 14 patients with acute myeloid leukemia (AML) was investigated by immunofluorescence and flow cytofluorometry. All tested blast populations expressed CD18/CD11a complex [leukocyte function antigen-1 (LFA-1)] and CD29 (very-late antigen (VLA)) and the majority were positive for CD54 [intercellular adhesion molecule-1 (ICAM-1), 78.6%] and CD56 [neural cell adhesion molecule (NCAM), 64.3%]. The expression of two other alpha chains of CD18/CD11b and CD11c varied considerably (64.3% and 42.8% of positive cases, respectively). Only one case (AML-M4) showed a weak expression of the activated platelet antigen CD41b. None of the tested blasts expressed the vitronectin receptor (CD61/CD51). No significant correlation between the expression of adhesion molecules and the FAB type of leukemia could be found. All tested blast populations were completely resistant to NK-mediated cytotoxicity and relatively resistant to LAK-mediated cytotoxicity in the standard 51Cr release assay. While no statistically significant correlation of the results in cytotoxicity assays with the expression of adhesion molecules or the expression of HLA-DR antigen could be observed, 2 out of 3 completely resistant cases lacked ICAM-1. These results show that even leukemic blasts which express all of the tested adhesion molecules can still be resistant to LAK-mediated cytotoxicity.