NK binding capacity and lytic activity depend on the expression of ICAM-1 on target bone tumours

Osteosarcoma cell lines are differently lysed by natural killer (NK) lympho cytes. A critical step in the lytic process is the recognition and attachme nt of effector to target cells. To determine binding capacity and lytic act ivity of NK cells, we investigated the distribution and role of ICAM-1, 2 a nd 3 on two osteosarcoma cell lines (HOS and Saos-2) in basal conditions an d after TNF alpha treatment. Modulation of ICAM-1 after TNF alpha treatment modified the binding capacity of NK cells to osteosarcoma target cells. Th is modulation process appears to play a critical role in determining the su sceptibility of these cells to NK-mediated lysis.