GANGLIOSIDES AND ANTITUMOR IMMUNITY

To elucidate the possible influence on the host's immune defense of ci ruclating gangliosides released from tumor cells, the effects of exoge neous gangliosides on the activities of some lymphocyte subpopulations were examined. The mono- and disialyllactosylceramides GM3 and GD3, w hich frequently are present in elevated amounts in sera of tumor-beari ng hosts, were found to inhibit strongly the cytotoxicity of natural k iller cells, to stimulate T-suppressor activity of peripheral blood ly mphocytes, and to inhibit their phytohemagglutinin-induced blast trans formation. All these effects may be linked to the ability of gangliosi des to modulate the arachidonic acid cascade in lymphoid cells, which for the first time was demonstrated in the course of our studies. Poss ible mechanisms underlying the immunomodulatory effects of serum gangl iosides as well as their role in the escape of tumor cells from immune surveillance and inhibition of the hosts immune system are discussed.