A SUPPORTIVE ROLE OF NEURAL CELL-ADHESION MOLECULE (NCAM) IN ADHESION BETWEEN LEUKEMIC BLASTS AND CYTOTOXIC LYMPHOCYTES

The expression and function of neural cell adhesion molecule (NCAM, CD56, Leu19) on leukaemic blasts was investigated. The expression of NCAM was frequent (64%) in 14 studied cases of acute myeloid leukaemia (AML) but not in chronic lymphocytic leukaemia (CLL: 1/3 cases positive) or immunocytoma (IC; no positivity). No correlation with the expression of other AM (intercellular adhesion molecule-1 (ICAM- 1), leucocyte function antigen-1 (LFA-1), VLA beta chain) or with AML type, according to FAB classification, was observed. Blocking of NCAM with anti-Leu 19 MoAb on AML targets resulted in a significant decrease of their susceptibility to LAK killing and in inhibition of conjugate formation. In the case of B prolymphocytic leukaemia (B-PLL) which did not express ICAM-1 or LFA-1 but was NCAM+, a complete resistance to LAK activity and lack of conjugate formation was observed. Blocking of NCAM on LAK effectors did not decrease their cytotoxic activity. Our results suggest that NCAM, in the presence of other AM, may have a supportive role in adhesion of leukaemic targets to LAK effectors.