In order to confirm the role of guinea pig lymphotoxin (GLT) in lectininduced cellular cytotoxicity (LICC), the effect of puromycin, a potent enhancer of GLT activity, on the LICC to target L·P3 cells induced by phytohemagglutinin (PHA) was investigated under serum-free conditions.
LICC was completely inhibited by puromycin, when it was added at the initiation of LICC culture, because of the inhibition of the release of GLT from the effector lymph node cells. However, LICC was markedly enhanced when puromycin was added several hours after the initiation of LICC culture. The interpretation of these facts is that GLT release can be inhibited by puromycin, but that the GLT already released exerts an enhanced cytotoxic effect on the target cells in the presence of puromycin. Enhancement of the cytotoxicity by the addition of puromycin several hours after the initiation of LICC culture was observed even after the removal of the GLT present in the supernatant, suggesting that the morphologically intact target cells were already affected by GLT in the early stages of LICC culture.