INHIBITION OF NK BINDING TO K562 CELLS INDUCED BY MAB SATURATION OF ADHESION MOLECULES ON TARGET MEMBRANE

Cell to cell interaction play a major role in the induction of a immun e response. NK cells represent a special lymphoid subset which display s its cytotoxic function without the engagement of MHC system. In orde r to investigate the role of different adhesion molecules in the mecha nism of binding of the NK cell to the classic tumor target K562 cell, we have employed different unclustered mAbs of the Adhesion session (5 th ''CD'' Workshop, Boston 1993) mostly of the CAM (cell adhesion mole cule) subpanel. After their reactivity characterization both on lympho cytes and K562 cells, those that demonstrate reactivity against the tu mor target were tested in the binding assay. The target was pretreated with the monoclonal in order to block a possible reacting molecule fo r the effector, Then, after the incubation of lymphocytes with PE-labe lled anti CD16 mAb, their ability to bind to the target was tested in flow. While the majority of the mAbs did not induce any significant ch ange in the binding capacity of the NK subset, few of them did, and pr ecisely anti-CD58 (LFA-3) and anti-CD54 (ICAM-1) which showed differen t level of inhibition, particularly drastic with S002, S083 and S100. Other mAbs, such as the S011 (anti-CD59), due to the presence of the P I-linked glycoprotein recognized on both target and effector membranes , and to its capacity to stimulate NK activity, produced a total bindi ng of the NK population. The coincubation of targets with anti- CD54 a nd anti-CD58 allowed to reduce at the lowest level this function. This data seem to support the hypothesis of specific surface molecules inv olved in the binding process of the NK cell, after recognition of the target.