Using this approach, induction of high titers of anti-Id antibodies and protection against tumor challenge was demonstrated (Campbell et al., 1987, 1990; Kaminski et al., 1987; George et al., 1988), even in animals with established lymphoma (Campbell et al., 1988), suggesting that, although nominally self-antigens, idiotypic determinants can become immunogenic when administered in a context that allows overcoming T cell tolerance. This evidence concerns the gene ID1 and neoplasm.