Anti-tumour antibodies in normal mouse sera

Evidence for the involvement of the immune system in surveillance against nascent tumors was sought by testing whether normal mouse sera were cytotoxic in the presence of rabbit complement for a variety of lymphoid and non-lymphoid tumor-cell lines. Tumour-reactive antibodies were detected in all mouse sera tested, including sera from congenitally athymic (nude) mice. Considerable variation was noted, however, in the levels of naturally occurring antibodies against specific tumor antibodies were identified as being predominantly IgM. The possible relevance of natural anti-tumor antibodies to immune surveilance was discussed.