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

Antigenic expression of CD54 and CD58 adhesion molecules was investiga ted on leukemic blast samples from ten patients with acute lymphoblast ic (ALL) and 14 with acute myeloblastic (AML) leukemia. The mean inten sity of fluorescence (MIF) was calculated and correlated with sensitiv ity of blast cells to the lytic activity of allogeneic lymphokine-acti vated 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 ca ses, it was absent in one case and expressed in less than 30% of blast s in two others, with an overall MIF of 3.0. CD58 expression was simil ar in both groups of patients, with an MIF of 7.6 in ALL and 7.0 in AM L. In addition, in six of the ten ALL cases and in two of the 14 AML c ases, leukemic blasts proved to be ''resistant'' to the cytotoxic acti vity of normal allogeneic LAK effectors. In these ''LAK-resistant'' pa tients, the CD54 antigenic expression was lower (p = 0.03) than in ''L AK-sensitive'' patients with an MIF of 1.7 vs 4.9 in ALL and 1.35 vs 1 2.9 in AML cases. Finally, blocking of CD54 and/or CD58 receptors on l eukemic blasts resulted in a slight reduction of Cr-51 release. Findin gs suggest that CD54 is differently expressed on myeloid and lymphoid blasts and that there is a correlation between CD54 MIF and susceptibi lity of blasts to the LAK activity.