Target Cell Lysis mediated by Soluble Cytotoxin released from stimulated Lymphocytes

MANY investigations have shown that lymphocytes stimulated with a specific antigen, or non-specifically by plant mitogens such as phytohaemagglutinin (PHA), release soluble mediators of various reactions^1–6. One of these mediators has been identified as a cytotoxic factor^{5, 6}, largely on the basis of its ability to inhibit ¹⁴C-amino-acid incorporation into L cells. The actual effect of this cytotoxic factor remains uncertain because other evidence of its cytotoxicity is meagre and because the observed decline in protein synthesis does not distinguish between cell lysis, growth inhibition and/or cell detachment. Furthermore, its biological significance has been questioned⁷, because other investigators have stated that intimate contact between lymphocyte and target cell is essential for lysis of the latter.