EXPRESSION OF ADHESION MOLECULES ON ACUTE LEUKEMIC BLAST CELLS AND SENSITIVITY TO NORMAL LAK ACTIVITY

Antigenic expression of CD54 and CD58 adhesion molecules was investigated on leukemic blast samples from ten patients with acute lymphoblastic (ALL) and 14 with acute myeloblastic (AML) leukemia. The mean intensity of fluorescence (MIF) was calculated and correlated with sensitivity of blast cells to the lytic activity of allogeneic lymphokine-activated killer (LAK) cells. CD54 antigen was expressed in all AML cases with an MIF of 11.2 while in ALL, though present in the majority of cases, it was absent in one case and expressed in less than 30% of blasts in two others, with an overall MIF of 3.0. CD58 expression was similar in both groups of patients, with an MIF of 7.6 in ALL and 7.0 in AML. In addition, in six of the ten ALL cases and in two of the 14 AML cases, leukemic blasts proved to be ''resistant'' to the cytotoxic activity of normal allogeneic LAK effectors. In these ''LAK-resistant'' patients, the CD54 antigenic expression was lower (p = 0.03) than in ''LAK-sensitive'' patients with an MIF of 1.7 vs 4.9 in ALL and 1.35 vs 12.9 in AML cases. Finally, blocking of CD54 and/or CD58 receptors on leukemic blasts resulted in a slight reduction of Cr-51 release. Findings suggest that CD54 is differently expressed on myeloid and lymphoid blasts and that there is a correlation between CD54 MIF and susceptibility of blasts to the LAK activity.