Distribution of inhibitory or activating 2B4 receptors in dNK-cell clones. dNK cell clones (n = 140) and pNK cell clones (n = 65) were assessed for cytolytic activity against the P815 target cells either in the absence or presence of an anti-2B4 mAb. The zero line refers to the spontaneous lysis of P815 by NK-cell clones in the absence of an anti-2B4 mAb. The cytolytic value per each clone represents the percentage of inhibition or activation of the spontaneous lysis obtained in the presence of an anti-2B4 mAb. Each spot represents the mean value of individual clones analyzed in 2 independent tests.