Some effects of neuraminidase on the in vitro interactions between spleen and mastocytoma (P815) cells

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Abstract
A recently advanced generalization is that a sialomucin coat surrounding tumour cells protects them from immunological surveillance. We have therefore studied the effects of neuraminidase (sialidase) on the immunolysis of P815 mastocytoma cells by sensitized spleen cells, in vitro, to test this hypothesis. In a very sensitive system in which immunolysis was quantitated by measurements of the release of 51Cr from labelled P815 cells, neuraminidase treatment of the target cells did not demonstrably make them more susceptible to attack by spleen cells. Killing proceeded in spite of a substantial contribution of sialic acid moieties to the net negative surface charge of the untreated P815 cells, and was not enhanced by enzymatic removal of substantial amounts of their bound surface sialic acids, as determined by cell electrophoresis. Thus, the generalization cannot be substantiated by our experiments. An interesting positive finding was that neuraminidase treatment of the killer, spleen cell population, enhances the 51Cr‐release from their targets.